An atypical case of atypical lipomatous tumor.

A 56-year-old woman was referred to us with an asymptomatic nodule on the thigh. The nodule was about 11x7 cm in diameter with a well-demarcated, smooth, surface. Magnetic resonance imaging showed the intensity of the nodule to be entirely monotonous or partially heterogeneous. Histological examination revealed a proliferation of adipocytes varying considerably in size and including many mono- or multivacuolated lipoblasts. Immunohistochemically, some of the tumor cells were positive for p53 and MDM2. Histologically, the atypical lipomatous tumor, lipoblastoma, spindle cell lipoma, pleomorphic liposarcoma, and hibernoma comprised the list of possible, differential diagnoses. We considered our case to be a variant of atypical lipomatous tumor, although it did not correspond to any of the 4 atypical lipomatous tumor subgroups. There has been no recurrence to date.