Multifocal recurrent adult rhabdomyoma.

The clinical and morphologic features of a recurrent, multifocal, adult, extracardiac rhabdomyoma are reported. This benign skeletal muscle neoplasm is composed of large round to polyhedral cells containing cross striations. The ultrastructural features consist of hypertrophic Z bands, intranuclear inclusions, and numerous mitochondria with linear, intracristal inclusions. The low thymidine labeling index and long potential doubling time correspond wi th the length of time for clinical recurrence.