[Melanosis of choroid plexus papilloma of the lateral ventricle: a case report].

A case of pigmented, well differentiated, choroid plexus papilloma is reported. A 45-year-old man came to our hospital complaining of attacks of vertigo and nausea. Skull X-ray films and CT scan demonstrated a calcified tumor in the left middle fossa. Tumor removal was done, and it was found that the tumor occupied the inferior horn of the left lateral ventricle. Histological examination revealed well differentiated choroid plexus papilloma containing various shaped pigment granules in the cytoplasm. The pigment granules in the tumor cells were stained black by Fontana-Masson method for melanin. The stain was negative in a section subjected to oxidative bleach. Granules were PAS-positive and autofluorescence. Therefore, the pigment granules had properties of both melanin and lipofuscin. In the electron microscopic study the ultrastructural appearance of the pigment was similar to that of neuromelanin, but not to that of pre-melanosome of neural crest origin. The pigment in this case seemed to be formed by "melanization" of lipofuscin as Barden's theory of pseudo-peroxidation. There are several case reports of pigmented choroid plexus carcinoma. However, no case of pigmented, well differentiated choroid plexus papilloma has, so far, been reported.