[Oncocytic carcinoid of the lung]

An observation of oncocytic carcinoid of the lung is described. The diagnosis was established by electron microscopic examinations which revealed a large number of mitochondria in cell elements of the tumor. Morphological differential diagnosis of this kind of carcinoid, particularly in the pre-operative period, is difficult because signs of oncocytic neoplasias such as large cell size, oxyphilia, and cytoplasmic granularity may be found in metastases of some kinds of cancers as well as in oncocytic adenoma of the lung.