RESUMO
Malignant hibernoma, also called round cell liposarcoma, is a subtype of liposarcome. It is composed of so-called mulberry cells with scanty stroma. The characteristic mulberry cell has a centrally located nucleus and multivaculoated foamy cytoplasm in which eosinophilic fat droplet granules are contained. The authors experienced a case of malignant hibernoma. The patient, 16-year-old male, had a slowly growing nontender firm solitary subcutaneous mass on the center of chin for about 6 months. He hadn't episode of trauma or exposure to X-ray irradiation on the chin. Histopathological findings of punch biopsied skin specimen revealed compact mulberry cells intermingled with normally matured fat cells in the deep dermis and muscle layer, but there were neither significant infiltrations of lymphocyte nor myxoid changes. The tumor mass was totally removed including surrounding tissues as much as possible. The surgically removed tissue specimen revealed brownish discoloration in the center. Histopathologically, it revealed numerous capillaries and massive extravasated erythrocytes like a hemangiona, just beneath the hibernoma mass. There was no evidence of local recurrence or metastasis during 2.5 years of post-operative observation.