Fig. 1

The tumors typically grew in a circumscribed manner, often with a well-formed, hyalinized fibrous capsule (a). Other features suggesting a slowly growing tumor, such as calcifications, were often present (b). Large numbers of foamy macrophages partially obscured the tumor cells (c). Close examination, however, showed atypical rhabdomyoblastic cells with enlarged, hyperchromatic nuclei (d). Desmin (e) and CD163 (f) immunostains highlight the neoplastic cells and macrophages