Oncocytic tumours.

Oncocytic tumours represent a distinctive set of lesions with distinctive granular cytoplasmic eosinophilia of the neoplastic cells. These cells are called oncocytes because of the "swollen" appearance they have as the result of a striking accumulation of mitochondria. Although generally uncommon, oncocytic tumours are by no means rare and have been reported, with different frequencies, in virtually every organ. A variety of biochemical and molecular changes have been identified, and the aberrant biogenesis of mitochondria in oncocytic cells bears intriguing similarities to that of a group of degenerative disorders known as mitochondrial encephalomyopathies. Although the relationship between the accumulation of mitochondria and the occurrence of tumours is unknown, investigation into the cellular alterations of oncocytes may further our knowledge of a variety of important biological processes such as proliferation, energy production and ageing.