Metastatic sarcomatoid renal cell carcinoma manifesting as a subcutaneous soft tissue mass

Metastases from visceral malignancies to subcutaneous soft tissues are relatively rare and their diagnosis requires a high level of suspicion. It is even more challenging if a metastatic lesion shows non‐specific high‐grade spindle cell morphology overlapping with various primary cutaneous and soft tissue tumors. We describe a unique case of subcutaneous metastasis of sarcomatoid renal cell carcinoma which was the first manifestation of the occult malignancy. The patient had a history of lipomas and dysplastic nevi and presented with an upper back mass. The mass, located superficially within the subcutis, was composed of atypical spindle cells arranged in a storiform pattern. By immunohistochemistry, the tumor cells were strongly diffusely positive for cytokeratin AE1/AE3 and vimentin and negative for Melan‐A, S‐100 protein, SOX10, melanoma cocktail, epithelial membrane antigen (EMA), p63, CK7, CK18, CK20, smooth muscle actin (SMA), desmin, CD34, TTF‐1, CD21, CD99 and bcl‐2. Scattered tumor cells were positive for MDM2 immunostain, but MDM2 amplification was not detected using fluorescent in situ hybridization (FISH). Co‐expression of cytokeratin and vimentin by the tumor raised the possibility of metastatic renal cell carcinoma and positivity of the tumor for PAX8 supported this hypothesis. A large renal mass was detected radiologically and the subsequent nephrectomy specimen showed high‐grade clear cell renal cell carcinoma with sarcomatoid features.     

Myoepithelioma of parotid gland presenting as infra-auricular subcutaneous mass

Myoepithelioma is a rare but well-characterized group of tumours, among which myoepithelioma of the salivary glands is the best known. We report two patients with myoepithelioma of parotid gland presenting as infra-auricular subcutaneous mass. The lesions were clinically suspected to be epidermal cyst. The biopsies revealed that most of the tumour cells showed epithelioid features with oval or spindle eosinophilic cytoplasm. No ductal or syringomatous epithelial structures were observed. The tumour cells showed cytoplasmic immunoexpressions of vimentin, cytokeratin (AE1/AE3), S-100 protein and smooth muscle actin (SMA). In one patient, a strong calponin positivity was observed. Maguetic resonance imaging (MRI) of both patients revealed exophytic, well-defined, strongly enhancing mass in superficial lobe of parotid gland, confirming the parotid gland origin. Myoepithelioma of parotid gland can be presented as a slowly growing tumour of pre- or infra-auricular area. In dermatologic department, it can be misdiagnosed as various dermal or subcutaneous tumours.     

Subcutaneous porocarcinoma clinically presenting as a soft tissue tumor

Porocarcinoma is a rare malignancy with glandular adnexal differentiation. A 38‐year‐old Japanese man noticed a subcutaneous mass in right inguinal region about 20 years prior to being examined. Radiological examinations demonstrated the mass, 11 × 10 cm in size, was in the subcutaneous fat tissue. Recently, the mass grew rapidly, and it was biopsied by an orthopedist based on clinical diagnosis of primary soft tissue tumor. Histopathological examination of the resected specimens also revealed that the tumor lacked involvement to the skin. Microscopically, the tumor was mainly composed of poroid cells with partially obvious squamous differentiation, accompanied by focal ductal structures immunoreactive for CEA and EMA. The tumor contained a low‐grade area consisting of poroid cells and high‐grade area with squamous differentiation. This histopathological heterogeneity suggested malignant transformation from poroma. The patient had the tumor in almost same size over the period of 20 years, which is the longest in the previous reports. This unique case of subcutaneous porocarcinoma is reported.     

Malignant TFE3‐rearranged perivascular epithelioid cell neoplasm (PEComa) presenting as a subcutaneous mass

Perivascular epithelioid cell neoplasms (PEComas) are a group of mesenchymal tumours with concurrent melanocytic and myogenic differentiation. Although many cases are sporadic, PEComas can be associated with tuberous sclerosis. A distinct subset of deep‐seated PEComas has been shown to carry TFE3 fusions. To our knowledge, this is the first reported case of primary subcutaneous malignant PEComa with molecular confirmation of TFE3 gene rearrangement.     

Malignant giant cell tumor of soft parts presenting as a skin tumor

Malignant giant cell tumor of soft parts is a rare neoplasm that histologically resembles a giant cell tumor of bone. It has a distinctive multinodular growth pattern and is composed of numerous osteoclast-like giant cells, histiocytes, and fibroblasts. Although this tumor is usually found in deep soft tissues, a superficial form has been described in the subcutaneous tissue and fascia. The authors report two patients, aged 75 and 78, with malignant giant cell tumors presenting as ulcerating skin nodules of the arm and foot. The tumors were relatively small, measuring less than 3.5 cm in greatest dimension, and involved the entire dermis and subcutaneous tissue. The clinical differential diagnoses included Kaposi's sarcoma, melanoma, and hematoma. Dermatopathologists and dermatologists should be aware of this entity to avoid confusion with other benign and malignant neoplasms that may contain multinucleated giant cells. The distinguishing histologic and immunohistochemical features of this tumor are discussed.     

Dermatofibrosarcoma protuberans presenting as a subcutaneous mass: a clinicopathological study of 15 cases with exclusive or near-exclusive subcutaneous involvement

Dermatofibrosarcoma protuberans (DFSP), a cutaneous fibrohistiocytic tumor of intermediate (borderline) malignancy, typically arises in the dermis and subsequently infiltrates the subcutaneous tissue. Very rarely DFSP may either arise within the subcutaneous fat without dermal involvement or show very extensive subcutaneous involvement with only minimal and clinically subtle dermal involvement. We present the clinicopathological features of 15 cases of DFSP showing exclusive or near-exclusive involvement of the subcutaneous fat. The differential diagnosis with other subcutaneous spindle cell neoplasms is emphasized. Awareness of this rare subset of DFSP should prevent its misdiagnosis as other less aggressive tumor types.     

Ectopic immature renal tissue presenting as a pedunculated sacral mass in a neonate

Ectopic immature renal tissue (EIRT) has been reported in a variety of tissues of mesodermal origin, including the dermis of the skin. We report a case of a newborn with a congenital lumbosacral mass with pathologic findings consistent with EIRT. This report highlights the clinical and pathologic considerations of EIRT, including associations with spinal dysraphism, teratoma, and Wilm's tumor.     

Gonococcal septicaemia presenting as a subcutaneous abscess.

In a case of disseminated gonococcal infection the diagnosis was delayed until Neisseria gonorrhoeae was grown from pus from a discharging abscess of the biceps muscle. This unusual skin manifestation appears not to have been reported before.     

Extra-abdominal desmoid tumor: an unusual subcutaneous lesion presenting as shoulder pain

A 50-year-old Hispanic woman presented to the medical walk-in clinic of a local community hospital complaining of shoulder pain. The problem had begun 9 months previously, and first manifested as dull right shoulder pain that developed after she carried a bag of groceries up one flight of stairs. A diagnosis of “muscle strain” and “arthritis” was made for which nonnarcotic analgesics were prescribed. The pain persisted, and 2 months later she was re-evaluated and diagnosed with degenerative joint disease. An orthopedics consultation was sought for further evaluation. During this examination, she pointed out to the physician that she had a “lump in her shoulder,” but she was informed that this was of no consequence and that her complaints were due to arthritis. Roentgenograms of the right shoulder and thoracic spine were performed and determined to be within normal limits. Once again she attempted to control the pain with nonsteroidal anti-inflammatory agents to no avail. Because the pain had become unbearable, she sought relief at the medical walk-in clinic. Physical examination was remarkable for a solitary, skin-colored, firm, deeply-seated tumor measuring 3×4 cm located over the right posterior of the deltoid. The mass was exquisitely tender to palpation and was fixed to the underlying muscle. There was a full range of motion as well as good muscle strength of the shoulder, but movement of the arm in any direction was painful. The patient subsequently underwent a deep, partial excisional biopsy of the lesion, and a firm white tumor mass of about 3 × 3 cm in size was dissected away from the deltoid muscle. Although the majority of the tumor was excised, visible portions of the lesion were not removed because they were present deep within the bulk of the muscle. Histopathologic examination revealed a large, deeply-seated poorly-circumscribed fibrous proliferation containing areas in which there were numerous spindle cells arranged in fascicles ( Figs 1, 2, and 3 ). Neither cellular atypia nor mitotic figures were seen. The diagnosis of extra-abdominal desmoid tumor was made. The patient subsequently underwent a wide re-excision of the area and tolerated the procedure well, developing normal function of the arm following surgery, although there was slight persistent tenderness of the deltoid. Because of the known association of desmoid tumors with familial polyposis coli ¹ , a barium enema was performed. No colonic polyps were demonstrated.

Figure 1 Open in figure viewer PowerPoint Histopathology of desmoid tumor at scanning magnification. There is a large, poorly-circumscribed, diffuse spindle cell proliferation that extends into the subcutis, muscle, and fascia (hematoxylin and eosin; original magnification, ×10)     

A "high-risk" epithelioid hemangioendothelioma presenting as a solitary, ulcerated, subcutaneous tumor

So-called "high-risk" epithelioid hemangioendotheliomas are uncommon neoplasms that demonstrate classic histopathologic features of epithelioid hemangioendotheliomas and a size larger than 3 cm or >3 mitotic figures per 50 high power fields. These neoplasms show an increased rate of metastasis (25% of cases) and are associated with a poor 5-year survival (59%). They may pose a diagnostic challenge for dermatopathologists as they mimic metastatic carcinoma, malignant mixed tumor, melanocytic neoplasms, epithelioid sarcoma, and epithelioid angiosarcoma. High-risk epithelioid hemangioendothelioma has not been previously reported as a solitary ulcerated mass in the skin. Here, we describe one such lesion that developed as a rapidly growing ulcerative skin tumor in a 33-year-old African American man with a remote history of Burkitt lymphoma. We also review the evolution and controversies in the understanding and classification of this neoplasm.     

Sarcoidosis presenting as multiple subcutaneous nodules

We report a young West Indian man who presented with non-specific constitutional symptoms and widespread subcutaneous nodules which were non-diagnostic on histology. The diagnosis of sarcoidosis was made on the basis of progressive bilateral hilar lymphadenopathy, interstitial pulmonary infiltration, a raised serum angiotensin-converting-enzyme level and a granulomatous hepatitis. All symptoms and signs improved dramatically on cortosteroid therapy.     

Malignant cutaneous glomus tumor presenting as a rapidly growing leg mass in a pregnant woman

A 21-year-old pregnant woman presented with a rapidly growing >2 cm nodule on her right leg, involving dermis and subcutaneous tissue. Histologically, the tumor was composed of sheets and nests of neoplastic cells with variable cytomorphology, including typical round to ovoid glomus cells with clear cytoplasm and well-defined cell borders, small cells and spindle cells. Numerous medium to large vessels were present throughout the tumor. Moderate- to high cellularity, nuclear atypia and frequent mitotic figures (42 MF/50 High power field (HPF)) were noted. Immunohistochemistry showed cytoplasmic and membranous expression of actin (HHF-35) and membranous expression of type IV collagen. The histologic features and immunoprofile were consistent with the diagnosis of malignant glomus tumor, a rare soft tissue neoplasm that typically arises on the extremities. Histologic features that infer malignancy in glomus tumors include the combination of large size (>2 cm) and deep location, or atypical mitotic figures, or moderate to severe cytologic atypia with high mitotic activity (>5 mitoses /50 HPF). Although our case was superficially located, the nuclear atypia and mitotic rate, as well as the large size, fulfilled the criteria for a malignant glomus tumor.     

Cutaneous sarcoidosis presenting as a testicular mass

Urologic involvement in sarcoidosis is rare. We report a patient who presented with a testicular mass and, shortly thereafter, manifested nasal lesions of the papular variant of cutaneous sarcoidosis. Histologic examination from both organ systems yielded sarcoidal granulomas. The patient was successfully treated using oral corticosteroids. Sarcoidosis continues to replace syphilis as "the great imitator of the 1990s," and clinicians must be increasingly aware of its variable presentations.     

Frontal mucocele presenting as a subcutaneous tumour on the forehead

A 57-year-old Japanese woman had a 3-month history of an asymptomatic subcutaneous tumour on the forehead. The patient presented a slightly elevated, elastic soft subcutaneous mass, 3 cm in diameter, on the mid to left-side forehead. Slight swelling of the left upper eyelid was observed. CT scanning and magnetic resonance images revealed a sharply demarcated cystic mass from the subcutaneous area on the forehead expanding into the frontal sinus and intracranial space. The tumour was diagnosed as a frontal mucocele and combined external and endoscopic approaches were performed. It is rare that a patient with a frontal mucocele is initially referred as a case of a subcutaneous tumour because most of the patients complain primarily of the ophthalmic symptoms. However, the present case reminds us that frontal mucocele is one of the differential diagnoses for a subcutaneous mass on the forehead.