Oncocytoma of the lung.

A tumor diagnosed as an oncocytoma was removed from the lower right lung of a 22-year-old patient. Specimens from the formalin fixed tumor were studied by light microscopy and by electron microscopy. Large numbers of mitochondria were observed in all the tumor cells at the ultrastructural level despite many artefacts due to fixation. The presence of two tumor cell types "typical" oncocytes and "condensed" oncocytes were demonstrated by electron microscopy. This appears to be the second pulmonary oncocytoma in which mitochondrial hyperplaxia has been demonstrated. The tumor was similar to previously reported cases of salivary gland oncocytomas.