Oncocytic variant of choroid plexus papilloma.

Two cases of oncocytic plexus papilloma are presented which were in the fourth ventricle and cerebello-pontine angle in women aged 70 and 63 years, respectively. The cytoplasm of the transformed tumor cells was enlarged, eosinophilic, and granular; and it was characterized ultrastructurally by innumerable mitochondria. Most of them had lamellar cristae, a clear matrix, and contained dense granules. These 'oncocytes' are identical with oncocytes of the human thyroid, parathyroid, bronchi, kidneys, adrenals, salivary gland and myocardium, and non-neoplastic choroid plexus epithelium. As far as we know, this is the first report of an oncocytic variant of the choroid plexus papilloma. Two unusual cases are described.