Intraoral multifocal adult rhabdomyoma. Report of a case and review of the literature.

Adult rhabdomyomas are uncommon, benign neoplasms of the head and neck region. They are usually solitary, but may rarely be multifocal. We report the clinical and morphologic features of a multifocal adult rhabdomyoma apparently present in the floor of the mouth of an elderly woman for 20 years. At the time of exploratory surgery, the surgeon believed there was diffuse multinodular enlargement of both sublingual glands. The differential diagnosis of a biopsy specimen that was taken for frozen section included salivary gland oncocytosis, a reactive process. On examination of permanent sections, however, the lesion was found to be a multifocal rhabdomyoma. No evidence of salivary gland tissue was found. Ultrastructural study demonstrated the characteristic attempts by this tumor to recapitulate its origin from skeletal muscle by the formation of abnormal contractile elements.