Stromal amyloid in pheochromocytomas.

Amyloid has been documented in the stroma of a number of neuroendocrine tumors. It is usually associated with elaboration of a polypeptide hormone product. Twenty-three adrenal pheochromocytomas occurring in 18 patients were graded for the extent of amyloid deposits on the hematoxylin-eosin-stained slides, confirmed to be amyloid by Congo red stain and polarization microscopy. Fourteen of 20 cases (70%) showed evidence of stromal amyloid; in two thirds of these cases, it was considered abundant. The awareness of amyloid deposits in approximately 70% of pheochromocytomas is important for surgical pathologists, as this occurrence has not been thought to be common in these tumors and might be a source of diagnostic difficulty.