Alzheimer's neurofibrillary tangles and paired helical filaments in the pheochromocytoma cells of the adrenal medulla--electron microscopic and immunoelectron microscopic observations. 
Alzheimer's neurofibrillary tangles (NFT) and paired helical filaments (PHF) were found in the pheochromocytoma cells of the adrenal gland removed from a 54-year-old female.  By electron microscopy they were identical to those found in the brains affected by dementia of Alzheimer type.  In the tumor cells, most of the PHF were found dispersed loosely in the cytoplasm, while typical NFT were infrequent.  By immunoelectron microscopy using peroxidase-antiperoxidase method, both NFT and dispersed PHF were stained positively with a polyclonal antiserum to human tau protein.  This is the first observation of NFT and PHF in paraneuronal tumor cells.  The patient has no obvious Alzheimer's disease.