Acinic cell carcinoma of parotid gland with prominent lymphoid stroma: A diagnostic dilemma

"Acinic cell carcinoma (ACC) with lymphoid stroma" represents a separate subgroup of salivary gland tumors with a thin fibrous capsule, a microfollicular growth pattern and a prominent lymphoid infiltrate completely surrounding the epithelial component. Lack of familiarity with this entity may create diagnostic problems. Recognition of this rare histologic variant is also important because it behaves far less aggressively than the conventional ACC. We describe cytological and histological findings in one such rare occurrence in the parotid gland of a 27-year-old female. Fine-needle aspiration of this mass revealed cohesive clusters of relatively uniform cells revealing mild pleomorphism, nuclear overlapping, frequent microacinar pattern, abundant granular/vacuolated/foamy/oncocytoid basophilic cytoplasm with ill-defined cytoplasmic borders. Background showed small mature lymphocytes, reactive lymphoid cells and lymphohistiocytic aggregates. Histopathological examination of resected tumor ACC with tumor cells containing periodic acid-Schiff positive diastase resistant granules arranged predominantly in microcystic pattern and surrounded by dense lymphoid stroma containing lymphoid follicle with prominent germinal centers.