Lump That Lies Again Tibia Mri Showed No Sign of Tumor

Introduction

Cutaneous and subcutaneous masses of the extremities incorporate a wide and potentially bewildering array of benign and malignant processes. It tin can be difficult to discover a description of lesions of this type in the musculoskeletal radiology literature, because these lesions are rarely identified or classified according to their superficial location and considering some of them are seen but by dermatologists, without radiologic evaluation. An understanding of the microscopic beefcake of the skin can aid in the formulation of a differential diagnosis (^,Fig ane). The pare consists of three layers: the epidermis, the dermis, and subcutaneous fat. The epidermis is the thinnest layer and is equanimous mainly of keratinocytes, with smaller populations of Langerhans cells, Merkel (neuroendocrine) cells, melanocytes, and unmyelinated axons. Underneath this layer lies the dermis, which consists of fibroblasts, endothelial and neural cells, and supporting elements such as a collagen matrix and the arrector pili muscles. The dermal layer also contains mast cells; macrophages; and specialized cells for hair growth, temperature regulation, and epithelial renewal. The apocrine glands secrete an oily fluid and are afflicted by catecholamines, while the eccrine glands secrete sweat. Both types of glands begin in the dermis and end at the skin surface. Below the dermis lies the subcutis or subcutaneous fat layer, which consists of lipid cells, nutrient vessels, and thin septa (^,ane,^,two).

From this myriad of cell types, a broad variety of benign and malignant soft-tissue lesions may arise. Many of the cancerous lesions may resemble benign ones at computed tomography (CT) and magnetic resonance (MR) imaging. Noesis of the patient's clinical history and pertinent laboratory test results, besides as an active dialogue with the referring physician, may enable a more curtailed differential diagnosis. The radiologist should exist familiar with the anatomic and histologic features, too equally the imaging characteristics, of these lesions.

The article provides a concise review and clarification of benign and cancerous soft-tissue lesions that arise in the epidermis, dermis, and sub-cutis as a result of disease, inflammation, or trauma.

Lesions of the Epidermis

Various lesions may arise from neural cells in the epidermal and dermal layers. Superficial neurofibromas may occur in the subcutaneous fat layer every bit well as the dermal and epidermal layers of the pare. In 1 report of patients with type 1 neurofibromatosis, 94% of superficial lesions extended to the skin surface (^,3). Nonetheless, most single neurofibromas are non associated with neurofibromatosis. The nodular blazon of superficial neurofibroma in both the superficial and the deeper locations sometimes can be distinguished from other cutaneous masses by virtue of the "target sign," a key zone of low signal intensity seen on T2-weighted images. The central zone is equanimous of longitudinal bundles of remainder nervus fibers or dense collagen and fibrillary tissue, which may account for the low bespeak intensity there; and myxoid textile may account for the higher peripheral signal intensity (^,3,^,four) (^,Fig 2). However, the target sign is seen in only approximately 21% of superficial lesions establish in patients with type 1 neurofibromatosis. The nigh common MR advent of superficial lesions in type i neurofibromatosis is a diffuse, poorly defined focus of heterogeneous signal intensity on T2-weighted images (^,3).

Hemangiomas are described according to the predominant blazon of vessel from which they originate, as clangorous, capillary, arteriovenous, or venous hemangiomas. The most frequent subcutaneous type is a capillary hemangioma, which is composed of small vessels with flattened endothelium. These lesions are found in the epidermal and subcutaneous layers. Lesions are usually identified in infancy or babyhood and may modify in size. Clangorous hemangiomas are dilated blood-filled spaces and are often intramuscular in location. They may contain phleboliths and other calcifications that can be seen on radiographs. Arteriovenous hemangiomas are acquired past abnormal communication of arteries and veins and may have a superficial or deep location. Some authors consider these lesions to be indicative of persistence of the fetal capillary bed. The deeper lesions may crusade bruits and an arteriovenous shunt. Venous hemangiomas also may contain phleboliths and, when seen in the extremities, are intramuscular in location (^,v). MR images may demonstrate fat elements within the tumor, as frequently occurs in cavernous hemangiomas. T2-weighted images may depict a serpiginous edge and feeding vessels (^,5). Information technology may be hard to distinguish lymphangiomas from clangorous hemangiomas, as both are multilocular cystic spaces. MR images show cavernous spaces also as a serpentine branching pattern in the lesions (^,Fig 3^,).

Granuloma annulare is the manifestation of a beneficial inflammatory procedure that may impact the epidermis, dermis, and subcutaneous fat layer of the skin. It is predominantly plant in children and young adults and may occur in a localized, perforating, generalized, or subcutaneous class. The localized grade, which is usually seen in the upper and lower extremities, may be manifested every bit multiple nodular ringed pare eruptions. The generalized form is similar to the localized type but has a wider distribution. The perforating form may extend to and penetrate the epidermis (^,6). The subcutaneous form is ever seen in children and bears a close histologic resemblance to a rheumatoid nodule. The meridian age of occurrence of this form is 2–v years. The lesion usually is a painless, solitary mass and frequently is plant in the pretibial region. Spontaneous regression has been seen, and local or distant recurrence has occurred in 19%–75% of cases (^,7). MR images depict an ill-divers subcutaneous mass (^,Fig 4^,) with a signal that is isointense on T1-weighted images and heterogeneously hyperintense on T2-weighted images when compared with the signal in muscle (^,vii). Lesions that show depression betoken intensity on both T1-weighted and T2-weighted images also have been reported; the signal intensity difference in such cases may be due to the degeneration of collagen within the mass (^,6). Treatment commonly consists of local excision. Since the nodules resemble those in rheumatoid arthritis, diagnosis may be aided by clinical and laboratory findings. Positive mucin staining is characteristic of granuloma annulare just not rheumatoid arthritis.

Leukemia cutis is defined as infiltration of the peel by leukemic cells, and its presence is associated with a grave prognosis (^,8). The epidermis, dermis, or subcutaneous fatty layer, or some combination thereof, may be infiltrated by neoplastic leukocytes. A item blazon of leukemia may be manifested in different types of pare lesions, even in the same patient: The clinical appearance of leukemia cutis may be that of ulcerative lesions, nodules, urticaria, or bullous lesions. Such lesions may be manifestations not only of leukemia but also of lymphoma (^,Fig 5^,).

Pigmented skin tumors are one of the nearly frequent reasons for dermatologic evaluation. MR imaging may be useful for differentiating melanoma from benign pigmented skin tumors such as blueish nevi and intradermal nevi (^,nine). Melanin has paramagnetic backdrop, and lesions with a higher melanin content have been shown to have higher or mixed signal intensity on T1-weighted images (^,10). In one small study, investigators showed that primary melanoma could be distinguished from metastatic melanoma and benign pigmented lesions by means of a tumor-to-fatty contrast ratio calculated on the basis of the appearance of these lesions on T2-weighted images (^,9). In full general, the T2-weighted signal intensity of malignant tumors was higher than that of subcutaneous fatty, whereas that of beneficial lesions was lower than that of subcutaneous fatty. The college T2-weighted signal intensity of cancerous lesions may be secondary to the presence of hemorrhage (^,ix). Other authors who investigated metastatic melanoma reported that, although there was no articulate correlation betwixt melanin content and signal intensity on T2-weighted images, a correlation was found betwixt melanin content and T1 shortening (^,10) (^,Fig 6^,). In the same study, tumors with no visible melanin paint at histologic assay included a greater number of lesions with hypo- to isointense signal on T1-weighted images and mixed signal on T2-weighted images when compared with the signal in muscle (^,x).

Lesions of the Dermis

Schwannoma is a benign lesion that arises from the Schwann cells of the nerve sheath. The tumor may be eccentric and may displace the peripheral nerve. Schwannoma is most commonly found in adults between the ages of twenty and 50 years. Ancient schwannoma, also known as degenerative neurilemmoma, may be found in an older patient population because it is a lesion of long elapsing. Most reported cases in the extremities are found in deep locations (^,11), just superficial schwannomas may occur in the dermal layer (^,Fig 7). Symptoms of tenderness and numbness are frequently reported at initial presentation. Calcification and ossification, perivascular hyalinization, and cystic necrosis are seen at histologic analysis, only a mineralized matrix usually is not seen on radiographs. Degeneration is hypothesized to occur over a long fourth dimension and is manifested on MR images as a focus of central necrosis, which may exist surrounded by a fibrous capsule (^,Fig 7). The lesions are well circumscribed. Most schwannomas are composed of Antoni type A and type B cells; withal, in ancient schwannomas, there is a loss of the type A cells and the tumor is equanimous largely of Antoni type B cells (^,11). Areas of necrosis may mislead the observer and cause a schwannoma to be misdiagnosed equally a sarcoma (^,11).

Cutaneous angioleiomyoma is an uncommon neoplasm; angioleiomyomas are more frequently establish in the uterus and the gastrointestinal tract (^,12). Dermatologists often treat cutaneous angioleiomyomas and, therefore, descriptions of the imaging features of this neoplasm are scarce in the literature (^,Fig eight^,). The lesions occur in the dermis and subcutis and may derive, in office, from the smooth muscle cells of the arrectore pilorum. Patients may nowadays with one or more painful alone subcutaneous nodules that are freely movable. The lesions are about frequently seen in the lower extremity and are associated with spontaneous precipitous pain. Discomfort might be elicited by such diverse stimuli equally a cold temperature or air current. The lesions occur more than frequently in women than in men, and pregnancy may increase the severity of pain. Some authors differentiate among solid, clangorous, and venous subtypes, but all subtypes comprise benign-actualization smooth muscle cells and vascular channels. In rare cases, nuclear pleomorphism and mitotic figures have been reported in these lesions. Small nervus fibers may be nowadays in the stroma or walls of these tumors; some investigators have hypothesized that such nerve fibers may exist the source of pain. Complete excision of the lesion is the handling of choice (^,12,^,xiii). The tumor may become malignant, degenerating into a superficial leiomyosar-coma, only this occurrence is rare; such lesions account for merely 2%–iii% of soft-tissue sarcomas.

Giant cell tumor of the soft parts is some other rare neoplasm, with the largest reported serial consisting of 22 cases (^,14). The neoplasm may be benign or malignant and has been observed in children and in adults up to 80 years old. The lesions are most commonly establish in the deep dermis or subcutaneous fat layer, but adjacent muscle invasion has been seen. The lower extremity is the most frequent location, followed by the trunk. At histologic analysis, the soft-tissue lesions closely resemble their osseous counterparts. Areas of stromal hemorrhage and hemosiderin deposition accept been noted in approximately 50% of the lesions. Metaplastic bone formation was seen in approximately forty% of the lesions in one instance series (^,xiv). Malignant behavior is very rare and may be associated with singular cells, including pleomorphic giant cells. Differential diagnosis, based on histologic findings, includes giant prison cell–rich extraskeletal osteosarcoma and giant cell–rich malignant gristly histiocytoma (^,15). The recurrence rate for giant prison cell tumor of the soft parts, at approximately 6%, is lower than that for its osseous counterpart (^,fourteen). Low-betoken-intensity foci within the lesions on T1-weighted and T2-weighted images have been documented and may reflect hemosiderin deposition (^,Fig 9^,) (^,16,^,17).

Dermatofibrosarcoma protuberans is a superficial neoplasm that arises in the dermis, just large lesions may extend into the deeper soft tissues. Lesions are seen most commonly in the torso only have been observed in both the upper and the lower extremities. Patients may nowadays with an indurated plaque that, over the course of several years, may develop into an ulcerated nodule (^,18). Males are more oft afflicted than are females, and the tumor almost unremarkably is seen in the 2d through fifth decades of life. Childhood dermatofibrosarcoma protuberans as well has been reported, and in this age group the lesion is found in the easily or anxiety (^,xviii). Local recurrence may be seen after resection, simply metastases are rare. The neoplasm contains spindle cells arranged in a storiform pattern. The MR appearance of the neoplasm is nonspecific, with signal often isointense to that of musculus on T1-weighted images and signal intensity college than that of fat on T2-weighted images (^,Fig x) (^,19).

Epithelioid sarcoma may be manifested as a subcutaneous mass or a nonhealing ulcer. The lesions begin in the dermis, and, in areas like the finger, where in that location is lilliputian subcutaneous fat, they may ulcerate through the skin surface. They may be painless and tedious growing and therefore easily ignored in the early on stages of disease. Tumors occur in the distal parts of the extremities, specially the manus and forearm, in young adults (^,Fig 11a^,). Patients besides may demonstrate palpable lymphadenopathy in the afflicted extremity (^{, ,}Fig 11b), and this event should prompt a search for potential tumor satellites at diagnosis. Regional lymph node dissection is recommended, and amputation of the digit is considered if a tumor is institute in the finger or toe (^,20). Radiographs may depict focal cortical thickening or stippled soft-tissue calcification. The tumor has a variable appearance on MR images: It may exist well marginated and homogeneous in a superficial location but infiltrative and heterogeneous in a deeper location (^,21). Deep-seated tumors may attach to tendon sheaths, fascias, and tendons or may spread forth neurovascular bundles and quickly disseminate disease (^,21). Histologic assay reveals large polygonal epithelioid cells with eosinophilic cytoplasm and vesicular nuclei. Broad infiltrative margins and a variable degree of nuclear pleomorphism and necrosis may be observed. Reported local recurrence rates are as high as 77%, and both recurrence and metastasis may have place many years afterwards an initial resection (^,21).

Cutaneous adnexal tumors consist of a broad range of benign and cancerous neoplasms. Lesions are classified co-ordinate to their site of origin in the apocrine, eccrine, or sebaceous glands. Many of the lesions behave in a benign style, just virtually all have a carcinomatous counterpart. As the tumors are irksome growing and asymptomatic, medical attending usually is not sought until pregnant local invasion by malignant lesions has occurred (^,22). Eccrine gland carcinomas are house subcutaneous nodules that occur in adults across a wide age range (eighteen–eighty years). The 5-yr survival charge per unit is approximately 60%. Eccrine glands are constitute everywhere on the torso, except the lips and parts of the ballocks. Immunohistochemical assay may help differentiate the carcinomatous variants of cutaneous adnexal tumors from other peel carcinomas. Duct formation may exist seen, with islands of malignant cells. The MR imaging appearance of the nodules is nonspecific (^,Fig 12^,). Primary therapy is surgical resection with a broad margin; only even with a wide margin, death may occur months or years subsequently an initial resection, secondary to lymph node involvement or distant metastases. Radiations therapy has been used with moderate success for local control, but chemotherapy is even so under investigation (^,23).

Merkel jail cell carcinoma is a rare ambitious neuroendocrine tumor. The Merkel cell is establish in the epidermis, where it is associated with a flattened axon final plate and may function as a mechanoreceptor for touch. Equally the neoplasm originates in the dermis and only rarely involves the epidermis, its origins have been questioned. Neurosecretory granules found in tumor cells suggest that the tumors derive from Merkel cells (^,24).

Patients may present with painless scarlet or violaceous nodules on sun-exposed skin. The age range for incidence of this tumor is broad, but most cases occur in adults older than 65 years. There is an increased incidence of this neoplasm in immunosuppressed patients with leukemia, an organ transplant, or rheumatoid arthritis. Tumors in the immunosuppressed population also may exist establish in patients younger than 65 years (^,25). At histologic assay, the tumor cell nuclei contain finely dispersed chromatin and have rounded contours. These features are helpful in eliminating melanoma, lymphoma, and cutaneous small cell epithelioid tumors from the differential diagnosis (^,26).

CT and MR images may show inflammatory fat stranding adjacent to the lesion (^,Fig 13) (^,27, ^,28). Other MR findings may include additional peel and subcutaneous tumor nodules aligned in a row and next large lymph node masses. MR imaging may be useful for evaluating patients for lymphatic interest. Side by side lymph node metastases were seen on MR images in 33% of patients in one case series (^,28). Compared with muscle, the lesions showed signal that was isoin-tense or slightly hyperintense on T1-weighted images and hyperintense on T2-weighted images. Large masses showed an inhomogeneous betoken on T2-weighted images (^,28). The prognosis is poor, although in that location are reported cases of spontaneous regression of the tumour and lymph node metastases, a process that is believed to be mediated by T-cell immunity. The response to chemotherapy may be short lived. The overall local recurrence rate is 25%, and regional lymph node metastasis occurs in an estimated 52% of cases. The disease takes a more aggressive course in transplant recipients, and 56% of those affected somewhen die of the illness (^,25).

Cutaneous metastases are oftentimes harbingers of avant-garde disease. The distribution of cutaneous metastases roughly parallels the overall incidence of visceral malignancies in the full general population. In a study of Veterans Administration patients, cutaneous metastases from lung cancer, melanoma, colon cancer, and genitourinary cancers were seen most oft (^,29). Approximately 75% of patients in the study population had a chief malignancy and widespread disease. Meta-static lesions normally were observed in shut proximity to the chief lesion site. Only xviii% of metastases occurred in the extremities, and these were nearly frequently from melanoma. Metastases from lung cancer and melanoma usually were confined to the dermis, and lesions of all types in near cases spared the epidermis (^,29). To our noesis, there is no description of these lesions in the radiology literature, nor is it known how frequently cutaneous metastases demonstrate characteristics of the index neoplasm. We have observed that the metastatic lesions vary in appearance.

Lesions of the Subcutaneous Fat Layer

Lipomas are the most common soft-tissue tumour, and superficial lipomas account for approximately 16%–50% of soft-tissue tumors. Superficial lipomas mainly are found in the subcutaneous fat layer, but lipomas also may occur in deep locations beneath the superficial fascia. Deep lipomas of the extremities are unremarkably intramuscular or infiltrating and may reach a much larger size than do superficial lipomas. A superficial lipoma unremarkably is soft and mobile on concrete examination and is rarely larger than 5 cm in bore. On MR images, lipomas accept bespeak intensity similar to that of adjacent subcutaneous fat. The lesions are separated from the subcutaneous fat by a thin capsule and may contain thin septa (^,xxx) (^,Fig fourteen^,).

Another lesion thought to derive from Schwann cells is the granular cell tumor, which occurs in both benign and malignant forms. Most benign lesions are found in the subcutaneous fat layer of the extremities, are four cm or less in size, and accept a round or oval shape. A granular jail cell tumor of the beneficial subtype may have low point intensity on T1-weighted and T2-weighted images (^,Fig 15), a feature that makes it indistinguishable from a benign gristly tumor. A peripheral rim of loftier signal intensity in benign lesions on T2-weighted images also has been reported (^,31). Literature most the imaging advent of the malignant subtype is deficient. A size of more than than four cm, a location in the deep soft tissues, and infiltration of side by side structures have been cited equally malignant characteristics. Malignant tumors also may have a more inhomogeneous betoken intensity than do benign tumors on T2-weighted images (^,31). Histologic evaluation reveals a prominent stromal component in the tumors and a ribbonlike system of tumor cells, both of which may account for the low indicate intensity seen on MR images (^,31).

Nodular fasciitis is a mutual soft-tissue neoplasm in young and heart-aged adults. Its most frequent manifestation is a subcutaneous nodule, but larger intramuscular forms as well have been reported. Lesions may exist tender or painful and are seen about frequently in the upper extremity, specifically the forearm (^,32). On T1-weighted images they may demonstrate a indicate that is isointense or hyperintense to that of muscle. On T2-weighted images, they may accept point that is hyperintense to that of musculus (^,Fig 16). Lesions appear round or oval and normally are well confining (^,33,^,34). Histologic examination may reveal hypercellularity, with plump fibroblasts bundled in fascicles (^,33). Some authors believe that the MR imaging characteristics of the lesions change according to the phase of their development. A myxoid matrix is visible in the early phase of germination. As the lesion matures, cellularity increases. Lesions of both histologic types may demonstrate high point intensity on T1- and T2-weighted images. Mature lesions oft are characterized by increased fibrosis, and the fibrotic areas have low signal intensity on T1- and T2-weighted images (^,34). Treatment is excision, and there is a low rate of recurrence.

Malignant fibrous histiocytoma is the most mutual soft-tissue sarcoma and is institute about frequently in the thigh. In one large case series, subcutaneous tumors constituted 43% of the lesions (^,35). Superficial subcutaneous tumors are smaller, and the superficial location implies a better prognosis. Such tumors may be confined to the subcutis or extend from the subcutis to the fascia (^,36). The longer overall survival of patients with superficial tumors may be related to the higher incidence in this group of tumors of the myxoid subtype, which is associated with a lower incidence of metastatases, equally well every bit to lesion size (^,35). Histologic subtypes include myxoid, storiform, pleomorphic, and inflammatory patterns. The storiform subtype is the ane nearly unremarkably found in the extremity (^,37).

MR imaging of soft-tissue malignant fibrous histiocytomas reveals lesions with intermediate to low bespeak intensity on T1-weighted images and inhomogeneous high betoken intensity on T2-weighted images (^,Fig 17^,). Images depict calcification in v%–20% of the lesions. High-grade myxoid lesions may appear cystic, and images acquired subsequently the administration of gadolinium reveal the nodular nonmyxomatous elements in tumors of this type (^,37).

Synovial sarcomas account for approximately 10% of all soft-tissue sarcomas. The 10-year survival rate for patients with these lesions is 11%–58%. Superficial lesions generally occur in the distal portions of the extremities or in paraarticular locations (^,38). The mean age at occurrence is thirty years. Favorable clinical factors include young age of the patient, tumor size of less than five cm, and tumor location in the distal part of the extremity (^,39). Several types of synovial sarcoma accept been recognized, including biphasic, monophasic epithelial, monophasic fibrous, and poorly differentiated synovial sarcomas. Monophasic tumors in the distal extremities imply a worse prognosis than do tumors of the biphasic type (^,38).

Soft-tissue calcification is seen in approximately 30% of synovial sarcomas. MR images may demonstrate circuitous signal characteristics, with fluid levels, hemorrhage, and septation in the lesions. Neoplasms with a bore of less than 5 cm may have a more than benign advent, with well-circumscribed margins and homogeneous high signal intensity on T2-weighted images (^,Fig 18) (^,40).

Inflammation-induced Lesions

Inflammatory processes such as gout and rheumatoid arthritis may produce lesions in both bone and soft tissue. Rheumatoid nodules frequently are seen in the subcutaneous soft tissues most pressure points and prominent bones, such every bit the heel pad. These soft-tissue lesions are easily diagnosed if at that place is radiographic evidence of arthritis in the next articulation. The MR appearance of rheumatoid nodules may vary from depression signal intensity on both T1- and T2-weighted images to heterogeneous increased signal intensity on T2-weighted images (^,Fig xix^,). Heterogeneous increased signal intensity has been noted in nodules with central necrosis (^,41). These nodules also may communicate with bursal sacs. Like rheumatoid arthritis, tophaceous gout may result in the formation of nodular soft-tissue masses that may contain calcification (^,Fig 20a^{, ,}). Low point intensity may be observed in the tophi on both T1- and T2-weighted images (^{, ,}Fig 20b, ^,20c); notwithstanding, signal intensity characteristics are nonspecific, as high betoken intensity on T2-weighted images also has been reported (^,42).

Kimura disease is an inflammatory disorder that is seen most often in Asian males who are in their 2nd or 3rd decade of life. Patients nowadays with painless masses, eosinophilia, and high serum IgE concentrations. Subcutaneous masses are seen most frequently in the head and neck and often involve the major salivary glands and regional lymph nodes. Upper-extremity masses also have been reported to occur in the epitrochlear regions. The etiology of this illness is unclear, merely laboratory findings are suggestive of an autoimmune response to an unknown stimulus. MR images may demonstrate bulky, poorly marginated subcutaneous soft-tissue masses with signal that is isointense to or slightly higher in intensity than the signal of muscle on T1-weighted images. Lesions all have high signal intensity relative to that of musculus on T2-weighted images and are homogeneously enhanced (^,Fig 21^{, ,}). The masses are equanimous of enlarged lymph nodes with eosinophilic infiltration in the paracortical areas, increased postcapillary venules, and hyperplastic lymphoid follicles. Handling may include surgical excision if conservative management with steroids is not constructive. The rate of recurrence is equally high as 25% afterward treatment with surgery alone, simply cancerous transformation has not been reported (^,43,^,44).

Trauma-related Lesions

Trauma-induced soft-tissue masses about often are institute in locations adjacent to prominent basic. Some patients, particularly children, do not recall the occurrence of injury. The subcutaneous fatty layer may demonstrate a multifariousness of signal intensity changes that correspond to the stages of fatty necrosis. Linear areas of edema with high bespeak intensity are commonly seen on T2-weighted images, but no well-demarcated soft-tissue mass is visible. In a chronic lesion, areas of low signal intensity appear on T1-weighted and T2-weighted images every bit fibrosis and hemosiderin deposits accumulate in the injured areas (^,45). If the patient has experienced high-velocity trauma, internal degloving may take identify around the pelvis, a condition that produces a Morel-Lavallée lesion. The skin and subcutis split from the fascia, producing a cavity that is filled with fluid and debris. Lesions are constitute effectually the thigh and accept a well-defined oval or fusiform shape. They are usually partially or wholly encapsulated (^,Fig 22^,). Signal intensity may alter from that seen in a hemorrhage to that typical in a seroma, depending on the chronicity of the lesion. Patchy internal or peripheral enhancement also may exist seen (^,46).

In summary, superficial soft-tissue masses are manifestations of a broad diverseness of beneficial and malignant processes. Knowledge of the patient's clinical history and straight visual exam of the lesion may assist narrow the differential diagnosis.

Figure ane.  Schema shows the layers and specialized structures of the skin.

Figure ii.  Type 1 neurofibromatosis in a 16-year-one-time girl. Axial T2-weighted fatty-suppressed MR image of the thigh shows a subcutaneous neurofibroma (arrowhead) with a low-betoken-intensity fundamental target sign and the excision site (pointer) of a previous neurofibrosarcoma.

Figure 3a.  Hemangiomatosis and lymphangiomatosis in a kid. (a) Coronal T1-weighted MR image shows reticulation in the subcutaneous fat of the upper function of the left leg (arrowheads). (b) Axial inversion recovery MR epitome shows a large central vessel (arrow) and a branching blueprint of reticulation (arrowhead).

Figure 3b.  Hemangiomatosis and lymphangiomatosis in a child. (a) Coronal T1-weighted MR paradigm shows reticulation in the subcutaneous fat of the upper office of the left leg (arrowheads). (b) Axial inversion recovery MR image shows a large primal vessel (arrow) and a branching design of reticulation (arrowhead).

Figure 4a.  Granuloma annulare in a 9-twelvemonth-old daughter. (a) Lateral radiograph of the tibia shows a superficial soft-tissue mass in the pretibial region (arrowhead). (b) Axial CT prototype shows a soft-tissue lesion (arrow) with an irregular superficial margin and lower attenuation than that in muscle.

Figure 4b.  Granuloma annulare in a 9-year-old girl. (a) Lateral radiograph of the tibia shows a superficial soft-tissue mass in the pretibial region (arrowhead). (b) Axial CT image shows a soft-tissue lesion (arrow) with an irregular superficial margin and lower attenuation than that in muscle.

Figure 5a.  Leukemia cutis in a 29-year-old man with astute T-cell lymphoblastic leukemia. (a) Photograph shows a purple macular rash on the man'due south confront and shoulders. (b) Sagittal T2-weighted prototype shows ulceration (arrowhead) in an intermediate-signal-intensity dermal and epidermal mass (arrow) on the back of the human foot.

Figure 5b.  Leukemia cutis in a 29-year-old man with acute T-cell lymphoblastic leukemia. (a) Photograph shows a purple macular rash on the man's face and shoulders. (b) Sagittal T2-weighted paradigm shows ulceration (arrowhead) in an intermediate-signal-intensity dermal and epidermal mass (pointer) on the dorsum of the foot.

Effigy 6a.  Principal melanoma on the plantar surface of the pes. (a) Short-axis axial T1-weighted MR paradigm shows a low-betoken-intensity neoplasm in the deep dermis and epidermis (pointer). The indicate in the lesion is isointense or slightly hyperintense compared with that in musculus. (b) Brusk-axis centric T2-weighted MR paradigm shows a balmy, inhomogeneous increment in signal intensity in the lesion (pointer).

Figure 6b.  Primary melanoma on the plantar surface of the foot. (a) Short-axis axial T1-weighted MR image shows a low-point-intensity neoplasm in the deep dermis and epidermis (arrow). The point in the lesion is isointense or slightly hyperintense compared with that in musculus. (b) Brusk-axis axial T2-weighted MR image shows a mild, inhomogeneous increase in indicate intensity in the lesion (arrow).

Figure 7.  Ancient schwannoma in a 42-year-former woman. Axial T2-weighted fat-suppressed MR paradigm shows a well-divers high-signal-intensity lesion (arrowhead) that contains a discrete central focus of necrosis with an sick-divers low-signal-intensity margin (arrow).

Figure 8a.  Cutaneous angioleiomyoma adjacent to the patella in a 26-twelvemonth-sometime man. (a) Axial T1-weighted MR image shows a well-divers, homogeneous, oval lesion (arrowhead) that appears to have invaded the capsule. The results of a histologic assay showed no capsular infiltration. (b) Centric T2-weighted fatty-suppressed MR image shows heterogeneous high signal intensity in the lesion (arrowhead).

Figure 8b.  Cutaneous angioleiomyoma next to the patella in a 26-year-old man. (a) Axial T1-weighted MR image shows a well-defined, homogeneous, oval lesion (arrowhead) that appears to have invaded the capsule. The results of a histologic analysis showed no capsular infiltration. (b) Axial T2-weighted fat-suppressed MR image shows heterogeneous high signal intensity in the lesion (arrowhead).

Figure 9a.  Giant cell tumor of the soft parts adjacent to the genu in a 71-year-old woman. (a) Sagittal T1-weighted MR image shows a round inhomogeneous lesion (arrow) in the subcutaneous fat. The lesion has higher indicate intensity than that in musculus. (b) Axial T2-weighted fat-suppressed MR image shows mildly increased bespeak intensity in most of the lesion (arrow) and a low-signal-intensity focus that may reverberate hemosiderin deposition.

Figure 9b.  Giant jail cell tumor of the soft parts adjacent to the knee in a 71-year-quondam woman. (a) Sagittal T1-weighted MR image shows a round inhomogeneous lesion (arrow) in the subcutaneous fat. The lesion has higher signal intensity than that in musculus. (b) Axial T2-weighted fatty-suppressed MR epitome shows mildly increased betoken intensity in virtually of the lesion (arrow) and a depression-signal-intensity focus that may reverberate hemosiderin deposition.

Figure 10.  Dermatofibrosarcoma protuberans of the foot in a 33-twelvemonth-one-time adult female. Short-axis axial contrast-enhanced T1-weighted fat-suppressed MR paradigm shows a lesion with marked inhomogeneous enhancement (pointer). The results of a histologic analysis demonstrated the penetration of the lesion through the dermis and subcutaneous fat layer to the fascia.

Effigy 11a.  Epithelioid sarcoma in the finger of a 52-twelvemonth-one-time man. (a) Sagittal T1-weighted MR paradigm shows a heterogeneous low-betoken-intensity neoplasm on the dorsal surface of the finger at the level of the middle phalanx (arrow). (b) Centric T2-weighted fat-suppressed MR image of the ipsilateral elbow shows an enlarged lymph node with inhomogeneous signal intensity (arrowheads).

Figure 11b.  Epithelioid sarcoma in the finger of a 52-yr-old human being. (a) Sagittal T1-weighted MR paradigm shows a heterogeneous low-signal-intensity neoplasm on the dorsal surface of the finger at the level of the middle phalanx (arrow). (b) Axial T2-weighted fat-suppressed MR prototype of the ipsilateral elbow shows an enlarged lymph node with inhomogeneous signal intensity (arrowheads).

Figure 12a.  Sweat gland carcinoma in the hand of a forty-twelvemonth-old man. (a) Coronal T1-weighted MR prototype shows an inhomogeneous mass (arrow) next to the offset metacarpal bone. (b) Axial dissimilarity-enhanced T1-weighted fat-suppressed paradigm shows the inhomogeneous enhancement and ill-divers edges of the mass (arrow).

Effigy 12b.  Sweat gland carcinoma in the manus of a 40-twelvemonth-onetime man. (a) Coronal T1-weighted MR image shows an inhomogeneous mass (arrow) adjacent to the first metacarpal os. (b) Centric contrast-enhanced T1-weighted fat-suppressed prototype shows the inhomogeneous enhancement and ill-defined edges of the mass (arrow).

Figure 13.  Merkel prison cell carcinoma in the upper arm of a 64-twelvemonth-onetime woman. Sagittal T1-weighted MR epitome shows an ill-defined lesion (arrow) located in the subcutaneous fat and extending to the dermis. The lesion has signal isointense to that in musculus and hypointense to that in adjacent fat. The subcutaneous fat stranding is indicative of inflammation.

Effigy 14a.  Lipoma in the subcutaneous fatty layer in the shoulder of a 30-twelvemonth-old man. Axial T1-weighted MR paradigm (a) and axial T2-weighted fat-suppressed MR image (b) show a discrete soft-tissue mass with internal bespeak intensity identical to that of fat (arrowhead) and, in a, a surrounding thin rim of low signal intensity that represents a capsule.

Effigy 14b.  Lipoma in the subcutaneous fat layer in the shoulder of a 30-year-old homo. Axial T1-weighted MR image (a) and axial T2-weighted fatty-suppressed MR image (b) show a discrete soft-tissue mass with internal signal intensity identical to that of fat (arrowhead) and, in a, a surrounding thin rim of low signal intensity that represents a capsule.

Effigy 15.  Granular prison cell tumor in a 24-twelvemonth-erstwhile woman. Coronal T2-weighted MR paradigm shows an oval lesion with depression signal intensity (arrow) in the subcutaneous fat of the pes, near the heel.

Figure 16.  Subcutaneous nodular fasciitis in a 33-year-erstwhile-man. Axial T2-weighted inversion recovery MR image shows a lesion (arrowhead) with a lobular contour, a thin surrounding capsule, and a low-signal-intensity core in the subcutaneous fat layer side by side to the fascia.

Effigy 17a.  Superficial cancerous fibrous histiocytoma in a 44-year-old man. (a) Coronal T1-weighted MR prototype shows a multilobulated depression-betoken-intensity lesion in the subcutaneous fat (arrowhead) adjacent to the iliotibial band, with edema (arrow) in the surrounding soft tissue. (b) Centric T2-weighted fatty-suppressed MR epitome shows inhomogeneous high indicate intensity in the tumor (arrowhead) and the surrounding region of soft-tissue edema (pointer).

Effigy 17b.  Superficial malignant fibrous histiocytoma in a 44-year-old man. (a) Coronal T1-weighted MR image shows a multilobulated low-signal-intensity lesion in the subcutaneous fat (arrowhead) adjacent to the iliotibial band, with edema (pointer) in the surrounding soft tissue. (b) Centric T2-weighted fat-suppressed MR image shows inhomogeneous high signal intensity in the tumor (arrowhead) and the surrounding region of soft-tissue edema (arrow).

Effigy 18.  Synovial sarcoma. Sagittal T2-weighted fat-suppressed MR image shows a well-defined homogeneous high-indicate-intensity lesion (arrowhead) with internal septa. The lesion is located on the superficial surface of the Achilles tendon.

Figure 19a.  Rheumatoid arthritis. (a) Short-centrality axial T1-weighted MR image of the foot shows depression-signal-intensity rheumatoid nodules (arrows) nether the metatarsal heads. (b) Short-axis centric T2-weighted inversion recovery epitome shows low bespeak intensity in most of the nodules (pointer), with peripheral areas of loftier signal intensity in the lateral lesions (conjoined arrows). Adventitial bursitis side by side to the lateral nodules (arrowhead) also is visible.

Figure 19b.  Rheumatoid arthritis. (a) Short-axis axial T1-weighted MR image of the foot shows low-signal-intensity rheumatoid nodules (arrows) under the metatarsal heads. (b) Short-centrality axial T2-weighted inversion recovery image shows low indicate intensity in most of the nodules (pointer), with peripheral areas of high bespeak intensity in the lateral lesions (conjoined arrows). Adventitial bursitis adjacent to the lateral nodules (arrowhead) also is visible.

Figure 20a.  Gout. (a) Axial CT image of the manus of a 44-twelvemonth-erstwhile woman shows calcification in tophi (white arrows) and a well-defined area of erosion (black arrow) in a phalanx. (b) Axial T1-weighted MR image of the talocrural joint of a 56-year-old man shows an intermediate-bespeak-intensity tophus adjacent to the lateral attribute of the fibula (arrow). (c) Axial T2-weighted MR image of the ankle shows a tophus (arrow) with both high-and low-indicate-intensity components.

Effigy 20b.  Gout. (a) Axial CT paradigm of the hand of a 44-year-former woman shows calcification in tophi (white arrows) and a well-divers area of erosion (black arrow) in a phalanx. (b) Axial T1-weighted MR epitome of the talocrural joint of a 56-twelvemonth-quondam homo shows an intermediate-signal-intensity tophus next to the lateral attribute of the fibula (pointer). (c) Centric T2-weighted MR image of the ankle shows a tophus (pointer) with both loftier-and low-point-intensity components.

Figure 20c.  Gout. (a) Axial CT image of the mitt of a 44-yr-former woman shows calcification in tophi (white arrows) and a well-defined area of erosion (blackness arrow) in a phalanx. (b) Centric T1-weighted MR image of the ankle of a 56-twelvemonth-old man shows an intermediate-point-intensity tophus adjacent to the lateral aspect of the fibula (pointer). (c) Axial T2-weighted MR image of the talocrural joint shows a tophus (arrow) with both loftier-and depression-betoken-intensity components.

Figure 21a.  Kimura disease. (a) Axial T1-weighted paradigm shows an inhomogeneous subcutaneous lesion in the thigh, with signal intensity higher than that of musculus (arrowhead). Fat stranding is visible at the lesion margin. (b) Axial T2-weighted image shows a peripheral region of high signal intensity and a central region of low indicate intensity in the lesion (arrowhead). (c) Sagittal dissimilarity-enhanced T1-weighted fat-suppressed image shows an ill-defined enhanced mass in the groin (arrowhead).

Figure 21b.  Kimura disease. (a) Axial T1-weighted paradigm shows an inhomogeneous subcutaneous lesion in the thigh, with signal intensity higher than that of muscle (arrowhead). Fat stranding is visible at the lesion margin. (b) Centric T2-weighted prototype shows a peripheral region of high signal intensity and a cardinal region of low point intensity in the lesion (arrowhead). (c) Sagittal dissimilarity-enhanced T1-weighted fat-suppressed epitome shows an ill-divers enhanced mass in the groin (arrowhead).

Effigy 21c.  Kimura disease. (a) Axial T1-weighted image shows an inhomogeneous subcutaneous lesion in the thigh, with betoken intensity higher than that of muscle (arrowhead). Fat stranding is visible at the lesion margin. (b) Centric T2-weighted image shows a peripheral region of loftier signal intensity and a fundamental region of depression betoken intensity in the lesion (arrowhead). (c) Sagittal contrast-enhanced T1-weighted fatty-suppressed image shows an sick-defined enhanced mass in the groin (arrowhead).

Effigy 22a.  Morel-Lavallée lesion in a 52-year-old woman after a motor vehicle accident. (a) Coronal T1-weighted MR image shows a fusiform homogeneous low-signal-intensity lesion in the subcutaneous fat layer (arrowhead) adjacent to the fascia. Fat stranding (arrow) also is visible. (b) Centric T2-weighted fat-suppressed image shows a fluid collection with a well-defined superficial margin and internal droppings (arrowhead), equally well equally fatty stranding (arrow).

Figure 22b.  Morel-Lavallée lesion in a 52-yr-old woman after a motor vehicle blow. (a) Coronal T1-weighted MR image shows a fusiform homogeneous low-indicate-intensity lesion in the subcutaneous fatty layer (arrowhead) next to the fascia. Fat stranding (arrow) likewise is visible. (b) Centric T2-weighted fatty-suppressed paradigm shows a fluid collection with a well-defined superficial margin and internal debris (arrowhead), likewise as fat stranding (arrow).

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Source: https://pubs.rsna.org/doi/10.1148/rg.265055729

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