Multiple myeloma masquerading as chromophobe adenoma.

A 62-year-old woman presenting with intracranial lesion eroding the sella with compression of optic chiasma was found to have plasmacytoma of the pituitary area. At the time of initial surgery, the patient had no biochemical, immunologic or marrow findings of multiple myeloma. The intracranial tumor was interpreted initially as chromophobe adenoma on light microscopy, but the diagnosis of plasmacytoma was established by electron microscopic examination of the tumor. The case illustrates the usefulness of electron microscopy as a diagnostic tool.