Acinic-cell carcinoma, papillary-cystic variant: A diagnostic dilemma in salivary gland aspiration

Fine-needle aspiration (FNA) plays a pivotal role as the initial diagnostic modality of choice when dealing with salivary gland (SG) lesions. Due to the heterogeneous nature of most SG neoplasms, cytologic interpretation on FNA can be quite challenging. This is particularly valid when dealing with rare tumor types, such as the papillary-cystic variant of acinic-cell carcinoma (ACC-PCV), resulting in a high rate of false-negative cytologic diagnoses. Seven cases of ACC-PCV diagnosed on tissue resection with a prior FNA performed in cytology were studied. Material consisted of Diff-Quik and Papanicolaou stained cytologic smears, as well as hematoxylin-eosin stained cell block and histopathologic sections. In no case did the FNA performed prior to the surgical resection eventuate in a cytopathologic diagnosis of cancer. A retrospective morphologic review of the smears disclosed several characteristics common to all 7 cases, i.e., mostly tightly cohesive fragments of neoplastic epithelium seen as monolayered sheets or with a prominent papillary architecture, high nuclear:cytoplasmic ratio ductal-type epithelium, cystic material and degenerated cellular debris, histiocytes, cells with squamoid and metaplastic oncocytic changes, vacuolated and pigmented histiocyte-like tumor cells, and lack of a predominant single-cell component or naked neoplastic cell nuclei. ACC-PCV represents a rare yet significant cause of false-negative results for cancer on SG aspirations. An erroneous interpretation may occur due to lack of experience in dealing with this tumor type, the rarity of published literature on ACC-PCV, and a predominantly cystic, somewhat variegated appearance of the tumor mimicking other benign and malignant SG lesions.