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M 65 y.o., FNA submandibilar mass
Warthin’s tumour (adenolymphoma, cystadenolymphoma, papillary cystadenoma lymphomatosum)

Warthin's tumour is the second commonest tumour involving the
major salivary glands. It often has a large cystic component
reflected in numerous macrophages, admixed with background
debris and lymphoid cells, including follicle centre cells as well as
the epithelial component. The epithelium is oncocytic, presenting
in flat sheets of cuboidal, well-outlined cells with dense
(non-vacuolated) slate grey (MGG) or bright eosinophilic (Papanicolaou)
cytoplasm. These can be admixed with mast cells. Aspirates
lacking either lymphoid or epithelial component can also be
suspected of being Warthin's tumour, but for definitive diagnosis
both lymphocytes and oncocytes must be present. Differential
diagnosis includes mucoepidermoid carcinoma which is often cystic.
The characteristic appearance of oncocytes in flat sheets with no
overlapping of nuclei and no cytoplasmic vacuolation helps to
distinguish the two.