title: Cytological features of cystadenocarcinoma in cyst fluid of the parotid gland: Diagnostic pitfalls and literature review.
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 x 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.
authors.affiliation: Department of Diagnostic Pathology, Kurume University Hospital, Kurume 19107, Japan. akihiko4@med.kurume-u.ac.jp
authors.forename: Akihiko
authors.initials: A
authors.lastname: Kawahara
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Harada
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Mihashi
authors.forename: Jun
authors.initials: J
authors.lastname: Akiba
authors.forename: Masayoshi
authors.initials: M
authors.lastname: Kage
mesh_terms: D020420:Cyst Fluid / Q000166:cytology*; D003536:Cystadenocarcinoma / Q000175:diagnosis* / Q000473:pathology*; D003951:Diagnostic Errors; D006801:Humans; D008297:Male; D010306:Parotid Gland / Q000473:pathology*; D010307:Parotid Neoplasms / Q000175:diagnosis* / Q000473:pathology*; D055815:Young Adult