Histopathological evolution of a cutaneous myxofibrosarcoma.

A 54-year-old woman presented with a 6-month history of a tender and swollen plaque appearing as a panniculitis affecting the left pretibial area. The initial histopathology revealed dermal and subcutaneous inflammation with interstitial histiocytes and mucinosis suggestive of either granuloma annulare or necrobiosis lipoidica. Over the subsequent 6 months the plaque grew progressively, despite treatment with topical corticosteroids under occlusion. Distal to the plaque reduced sensation developed in the limb. Biopsies of the nodular areas now revealed a dense dermal infiltrate of atypical spindle cells within a prominent myxoid stroma and a pleomorphic multinucleated epithelioid cell component. These features were those of an intermediate grade myxofibrosarcoma. This soft-tissue sarcoma may initially masquerade clinically as a panniculitis and a granulomatous process on biopsy as in our patient, leading to a delay in surgical therapy.