Rhabdomyoma of the base of the tongue.

The histopathological and imaging findings of a rhabdomyoma of the base of the tongue were studied. An immunohistochemical examination of the tumour cells showed positive immunostaining for myoglobin, desmin, and striated muscle actin, but negative immunostaining for smooth muscle actin. Electron microscopy showed many glycogen granules and mitochondria in the tumour cells. The T2-weighted and contrast-enhanced magnetic resonance images (MRI) clearly delineated morphological features of this tumour, but T1-weighted MRI and computed tomography (CT) images showed no important features. These findings are typical for an adult extracardiac rhabdomyoma located in the head and neck region, and they will be useful for diagnosis of this tumour.