Oncocytic myoepithelioma and pleomorphic adenoma of the salivary glands

Twenty oncocytic myoepitheliomas (MEs) and pleomorphic adenomas (PAs) were composed of interlacing fascicles of swollen spindle-shaped or/and epitheli oid oncocytic myoepithelial cells showing intense finely granular immunorea ctivity with anti-mitochondrial antibody. Focal vacuolation of the cytoplas m of oncocytic myoepithelial cells and their gradual transition into sebace ous metaplasia were observed in 3 cases. Another unusual feature found in 5 cases was the presence of slit-like adenomatoid spaces lined with double-l ayered oncocytic myoepithelium closely resembling Warthin's tumour. The nuc lei of oncocytic cells were characterized by enlargement, hyperchromasia an d polymorphism, which should not be confused with malignancy. Oncocytic cha nge in myoepithelial cells in MEs and PAs can cause pitfalls in the differe ntial diagnosis of salivary gland tumours. We describe some unusual histolo gical features associated with onococytic metaplasia in benign myoepithelia l cell-derived salivary gland rumours, hoping to help to avoid the overdiag nosis of malignancy.