Pleomorphic adenoma with extensive oncocytic papillary cystic areas and trichilemmal keratinisation - A unique presentation.

Pleomorphic adenoma (PA) is a commonly occurring benign salivary gland tumour known for its surfeit of histo-morphologic appearances ranging from myxochondroid, plasmacytoid, and squamoid elements to the infrequently seen osseous and adipose tissue metaplasia. Oncocytic metaplastic changes, a rare finding, present in the form of sheets/islands/cords of polygonal cells with rich eosinophilic or occasionally clear cytoplasm and an oval/round nucleus. We report one such rare case which portrayed extensive oncocytic changes in a unique bilayered/multi-layered epithelium, lining the papillary cystic areas similar to that of Warthin's tumour and extensive keratinisation simulating the newly recognised entity "adnexa-like differentiation/trichilemmal keratinisation", along with foci of cholesterol clefts and multi-nucleated giant cells.