Rhabdomyoma of the tongue. Report of a case with light microscopic, ultrastructural and immunohistochemical observations.

Adult rhabdomyoma is a benign neoplasm of skeletal muscle origin, which mainly occurs in the head and neck region. Because of its rarity the diagnosis may be missed, especially if cross-striations cannot be demonstrated by light microscopy. By applying supplementary diagnostic evaluation with immunohistochemistry and electron microscopy, the diagnosis is established. Positive staining with desmin unequivocally demonstrates that the tumour cells are derived from muscle tissue. The presence of myofibrils, Z-bands and numerous mitochondria by ultrastructural examination are characteristic features of this tumour.