Sarcomas with combined features of liposarcoma and leiomyosarcoma. Study of two cases of an unusual soft-tissue tumor showing dual lineage differentiation

Two cases are described of a soft-tissue sarcoma characterized histologically by the intimate admixture of areas displaying the features of liposarcoma and leiomyosarcoma. Both cases occurred in men, 70 and 77 years of age. The lesions were located in the left scrotum and abdominal cavity, respectively. Histologically, the lipomatous component in both cases consisted predominantly of well-differentiated liposarcoma with myxoid areas. The smooth-muscle component was characterized by intersecting fascicles of spindle cells displaying nuclear atypicality and scattered mitotic figures; the spindle cells in these areas were strongly immunoreactive with actin and desmin antibodies. The above tumors must be distinguished from angiomyolipoma, spindle-cell lipoma, myolipoma of soft tissue, and more importantly, from "dedifferentiated" liposarcoma. The development of dual lineage differentiation within adipose tissue tumors as exemplified by these two cases may be more prevalent than has been generally recognized, and may require the application of immunohistochemical markers for specific identification of the spindle-cell component.