Membrane-bound paracrystalloid structures in alveolar rhabdomyosarcoma.

We report here a case of an alveolar rhabdomyosarcoma in a 25-year-old woman. Ultrastructural examination revealed a few periodical membrane-bound crystalloids, similar to those regarded as specific for alveolar soft-part sarcoma. Our study provides evidence supporting a myogenic origin of those periodic structures, and simultaneously a myogenic origin of alveolar soft-part sarcoma.