Rhabdomyoma of the retroperitoneum. A report of a tumor with both adult and fetal characteristics: a study by light and electron microscopy, histochemistry, and immunochemistry.

An unusual benign tumor of skeletal muscle origin is described. The tumor was located in the left retroperitoneum of a newborn female. The tumor contained features of both an adult and fetal rhabdomyoma when studied by light and electron microscopy, immunocytochemistry, and histochemistry. This is the only report of this type of neoplasm in the literature.