Oncocytic cystadenoma of the parotid gland with prominent signet-ring cell features.

A case of distinctive benign cystadenoma of the parotid gland composed of several different morphological components is presented. The most conspicuous morphological component and the largest part of the neoplasm was represented by solid sheets of oncocytic cells surrounded by myoepithelial cell layer. Most oncocytic cells possessed large intracytoplasmic vacuoles with the nuclei displaced towards the periphery, imparting them with a striking signet-ring cell appearance. The size of the intracytoplasmic vacuoles ranged from 4 to 50 microm. Immunohistochemically these signet-ring cells lacked immunoreactivity for S-100 protein and cytokeratin but they strongly stained for antimitochondrial antibody 113-1. The present case illustrates an unusual, hitherto undescribed, morphological feature of benign oncocytic cystadenoma of the parotid gland.