Adenoid cystic carcinoma: A study of 19 cases of salivary and extra-salivary tumours diagnosed by fine needle aspiration cytology.

Background: Adenoid cystic carcinoma (ACC) arises at sites where seromucinous or sweat gland epithelium is present and commonly affects the salivary glands. Rarely it can occur at extra-salivary locations.

Methods: A retrospective analysis of 19 cases of ACC diagnosed on fine needle aspiration cytology (FNAC) over a period of 15 y (2002-2016) was made.

Results: Of 19 total cases, there were 10 salivary and 9 extra-salivary ACCs. Extra-salivary tumours were seen in 2 cases each in trachea, tongue and in one case each in bronchus, lung, subcutaneous tissue, maxillary antrum, and external auditory canal. The age ranged from 14-80 y (mean: 49.5 y), 10 patients were male and 9 were female. The smears were highly cellular in 11 cases, moderately cellular in 5 cases while 3 cases were paucicellular. Multilayered dense clusters, tissue fragments, dispersed cells and cup-shaped fragments were seen. Relatively uniform cells with high nuclear: cytoplasmic ratio, hyperchromatic nuclei, irregular margins, and nuclear moulding were observed. Variable sized hyaline globules, finger-like hyaline material, hyaline cylinders, and hyaline cords were noted. The cytologic diagnosis of ACC was rendered in 13 cases while in 6 cases it was one of the differential diagnosis including monomorphic adenoma, membranous variant of basal cell adenoma, adnexal tumour, polymorphous adenocarcinoma, and pleomorphic adenoma (PA).

Conclusions: Cytologists must be aware of varied locations where ACC can occur. A diagnosis of ACC must not rely exclusively on the occurrence of hyaline globules but necessitates a close scrutiny of cellular and nuclear features to avoid diagnostic pitfalls.