Lipoleiomyosarcoma of the mediastinum.

A case is described of a mediastinal soft tissue sarcoma, in a 76-year-old man, characterized microscopically by the intimate combined features of liposarcoma and leiomyosarcoma. The lipomatous component consisted of well differentiated liposarcoma with myxoid areas. The smooth muscle component was characterized by fascicles of spindle cells showing nuclear atypia and scattered mitoses. The spindle cells displayed intense reactivity for alpha smooth muscle actin (ASMA), desmin and vimentin. Differential diagnoses included dedifferentiated liposarcoma, spindle cell liposarcoma, angiomyolipoma and myolipoma. To the best of our knowledge no case of sarcoma in the mediastinum with combined features of liposarcoma and leiomyosarcoma has been reported. The dual lineage differentiation of the lipoleiomyosarcoma may be difficult to identify in small biopsy samples which may not represent the tumor as a whole. Lipoleiomyosarcoma should be included in the differential diagnosis of soft tissue tumors arising in the mediastinum.