Skeletal muscle differentiation in Wilms' tumor. Antibody identification and explant culture.

We studied a case of Wilms' tumor with focal areas of well-differentiated skeletal muscle by immunoperoxidase staining using anti-skeletal muscle myosin and by tissue culture explant of the tumor. Strong immunostaining occurred in areas of well-differentiated muscle but also occurred in focal areas where the cells were undifferentiated. The primary explant of this tumor was attempted using standard serum-containing culture media and a serum-free hormonally defined culture medium. While serum-containing culture media gave rise to a fibroblastlike cell population, the serum-free hormonally defined medium produced cells of myoid origin. Ultrastructurally, all stages of early myogenesis from myoblasts to myotubules were observed in this primary explant grown in serum-free medium.