Atypical lipomatous tumors with smooth muscle differentiation: report of two cases.

Two cases of soft-tissue atypical lipomatous tumors with areas of smooth muscle cell differentiation are presented. The patients were a 72-year-old man (Case 1) and a 62-year-old woman (Case 2); their neoplasms were located in the left inguinal region and on the chest, respectively. The adipocytic component in Case 1 contained cells with nuclear atypism and lipoblasts. Case 2 showed only slight nuclear atypism and lacked any lipoblasts. Smooth muscle fascicles were composed of well-differentiated cells with a few mitoses having none or only a slight atypism. They expressed muscle-specific actin and desmin in both cases. No recurrence was recorded during the follow-up time.