Abstract
Cystadenocarcinoma is a rare malignant tumor, with an estimated incidence of 2% of malignant salivary gland tumors. Cytological diagnosis of cystadenocarcinoma is important for differential diagnosis between benign lesions and malignant tumors with cystic growth. We report a case of cystadenocarcinoma causing difficulty in cytological diagnosis. A 23‐year‐old man presented with an asymptomatic mass in the left parotid gland that had been present for 2 years. The mass was elastic hard, measuring 30 × 35 mm in diameter. Preoperative fine‐needle aspiration cytology (FNAC) showed a small number of tumor cell clusters in the cystic fluid. The cluster was arranged in a ball‐like structure and was cohesive with overlapping. Tumor cells had a small vacuolated, soap‐bubble appearance in the cytoplasm. The papillary‐cystic variant of acinic cell carcinoma (ACC‐PCV) was suggested from these findings on FNAC. Histologically, the tumor was not encapsulated, but formed large cystic spaces against a background of fibrous connective tissue. The tumor cells in the cystic dilated duct showed papillary structures, which were continuous with the lining cuboidal cells. There was neither a definite double‐layered arrangement in cystic ducts and solid islands nor histological findings characteristic of the papillary‐cystic or follicular pattern of ACC‐PCV. As tumor cells with a small vacuolated, soap‐bubble appearance of the cytoplasm are common findings of both cystadenocarcinoma and ACC‐PCV, they are of little use for differentiation; however, they are so characteristic that the majority of benign salivary gland lesions with cystic structures can be excluded, if enough attention is paid. Diagn. Cytopathol. 2010. © 2009 Wiley‐Liss, Inc.