PLEOMORPHIC ADENOMA

• It is a well circumscribed tumour with complete or partial encapsulation with dense fibrous tissue.

• Epithelial components include proliferating ductal and myoepithelial cells forming ductal structures containing eosinophilic material.

• These cells also may form sheets, strands or islands.

• Ductal cells are cuboidal in shape with scanty cytoplasm.

WARTHIN TUMOUR

• Warthin tumour is made up of epithelial component and lymphoid component.

• Cystic formation, papillary projections are seen, showing germinal centres.

• The cyst are lined by papillary proliferation of bilayered oncocytic epithelium.

• The epithelial cells are abundant, finely granular, eosinophilic and are arranged in two layers.

• The inner luminal layer consists of tall columnar cells with centrally placed, palisaded and slightly hyper-chromatic nuclei.

• The outer luminal layer consists of cuboidal or polygonal cells with more vesicular nuclei.

MUCOEPIDERMOID CARCINOMA

• Microscopically, three types of cells are seen, dispersed in the connective tissue stroma.

• First type is Epidermoid cells which are squamous with distinct intercellular bridges, rarely with evidence of keratin formation.

• Second type is mucous secreting cells which are ovoid, filled with mucin and peripherally placed nucleus (clear cells)

• Intermediate cells are another type of cells, ovoid with darkly staining nucleus and scanty eosinophilic cytoplasm.

ADENOID CYSTIC CARCINOMA

• The tumour is composed of uniform cells resembling basal cells arranged in anastamosing whorls or duct like pattern.

• Some of these duct like areas contain mucoid material.

• This feature gives rise to the characteristic appearance described as “cribriform”, “honeycomb” or “swiss cheese” pattern.

• There may be areas where the cells are tubular or more solid

• The connective tissue components is often hyalinized and surrounding the tumour cells, forming a structural pattern of cylinders (ACC aka cylindroma).

Source: Maji Jose