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Case Reports

Abstract

Liposarcoma is the most common type of sarcoma in adults. Dedifferentiated liposarcoma is a rare variant with potential for metastasis and local recurrence.  Cutaneous presentations, or superficial liposarcoma, are rarely encountered. We present a case of primary cutaneous dedifferentiated liposarcoma. 71-year-old male presented with a tan-brown to violaceous nodule on the left thigh with no appreciable underlying mass. Past dermatology history included keratinocyte carcinoma, primary cutaneous marginal zone B-cell lymphoma in remission, and stage IIIB melanoma currently under surveillance. Punch biopsy revealed an infiltrative dermal proliferation of severely atypical spindled cells with rare atypical mitotic figures within a dense collagenous stroma, showing no specific morphologic features of differentiation. Immunohistochemical studies showed focal desmin expression and were negative for S100, ERG, myogenin, and caldesmon. p53 immunostain exhibited a wild-type expression pattern, while MDM2 showed strong staining in the atypical cells. Fluorescence in situ hybridization was done and identified 12q15 MDM2 amplification. CT chest, abdomen, and pelvis were negative for a retroperitoneal process or pulmonary metastases and an MRI of left lower extremity showed only focus of atypical subcutis without mass effect. The imaging and pathologic findings were consistent with superficial dedifferentiated liposarcoma. Surgical resection revealed a dedifferentiated liposarcoma (1.1 cm) arising from an atypical lipomatous tumor (15.2 cm). Superficial dedifferentiated liposarcoma most commonly occurs in the extremities. Dedifferentiation entails a risk of metastasis unlike well differentiated/atypical lipomatous tumors. Large size (>8 cm) and lung metastasis at diagnosis have been associated with a poorer prognosis. Mainstay treatment is surgical resection.