Smooth muscle in atypical lipomatous tumors. A report of three cases.

Three cases of atypical lipomatous tumor with areas of smooth muscle are presented. The patients were a 49-year-old man, a 45-year-old woman, and a 63-year-old man; their neoplasms were located in the spermatic cord, the mediastinum, and the retroperitoneum, respectively. The smooth muscle foci were well differentiated in all cases. Smooth muscle was present in the primary tumor in the first and second cases (spermatic cord and mediastinum) and in a recurrence in the second case (there has been no recurrence in the first case). In the third case (retroperitoneum), smooth muscle was found only in a recurrence; it was absent from later recurrences, which showed the features of dedifferentiated liposarcoma. The smooth muscle component did not appear to influence the behavior of the tumor in any case.