Secretory carcinoma of the parotid with adenoid cystic carcinoma cytological pattern: A cytological-pathological correlation with literature review.

Secretory carcinoma (SC) is a rare low-grade malignant tumor, defined by ETV6-NTRK3 fusion, identifiable by FISH. We describe a case in a 58-year-old male with a painless slowly growing 16mm palpable mass within left superficial parotid. FNA of the mass showed highly cellular specimen with moderate to large pleomorphic cells with round to ovoid nuclei with vesicular chromatin and distinct nucleoli. Cells had moderate to large amounts of vacuolated cytoplasm. Abundant globular metachromatic material, resembling that of adenoid cystic carcinoma, was noted. This material was seen extracellularly and intracytoplasmic, and stained magenta on Diff-Quik and blue-green on Papanicolaou-stained slides. The tumor cells on a cell block preparation were positive for Mammaglobin and S-100. PAS stain highlighted extracellular and intracytoplasmic secretions. FNA diagnosis was "Positive for Malignancy. Morphologic features most compatible with Mammary Analogue Secretory Carcinoma". ETV6 FISH studies as well as histologic examination of excised tumor confirmed the diagnosis. Finding the globular metachromatic material in SC, that is generally seen in adenoid cystic carcinoma, broadens a cytological differential diagnosis of both entities. Cytological differential diagnosis, clinical, histological, immunohistochemical, and molecular features of secretory carcinomas are discussed in this study.