Primary pigmented carcinoma of the choroid plexus. A light and electron microscopic study.

Pigmented carcinoma of the choroid plexus was found in a 33-year-old man. Autopsy revealed no primary tumor in the skin or eyes. A slightly cystic pigmented tumor was present in the right lateral ventricle infiltrating the thalamus and striatum. Metastatic implants were found in both temporal lobes and the cerebellum. The spinal cord was covered by black meningeal nodules, and the cauda equina was completely encased by the tumor. Metastases were found in the liver, pancreas, and kidney. Microscopically the mass contained normal choroid plexus with psammoma bodies adjacent to carcinomatous epithelium forming prominent papillae and tubules. Melanin granules were found within the neoplastic cells and in the stroma. Electron microscopy demonstrated melanin granules in various stages of development in the cells, which were joined one to another by desmosome-like structures. This is the second reported case of pigmented carcinoma of the choroid plexus and the first with metastases outside the central nervous system.