A Case of Parotid Secretory Carcinoma Diagnosed by Preoperative Cytology

Abstract

Secretory carcinoma is a tumor for which the disease concept has only recently been established. Secretory carcinomas occur most frequently in the parotid gland (50%–70% of cases). They have a predilection for subjects in their 40s, and the incidence tends to be slightly higher in males. It is estimated that 10% of all salivary gland carcinomas are secretory carcinomas. The histology is similar to that of acinic cell carcinoma, and the diagnosis is often difficult to make by preoperative cytology. Detection of the ETV6-NTRK3 fusion gene plays an important role in the definitive diagnosis of secretory carcinoma. We report a case in which the fusion gene ETV6-NTRK3 was detected by preoperative cytological diagnosis.

The patient was a 51-year-old man who visited our hospital with the chief complaint of a gradually enlarging mass in the right parotid region. Examination revealed a mass in the right parotid region measuring 20 mm in diameter, and fine-needle aspiration was performed. Cytological examination revealed a papillary cystic arrangement of cells that were thought to be of epithelial origin, and immunohistochemical study showed positive staining for S-100 (+), mammaglobin (focal+), CK19 (+); the ETV6 split signal was observed by FISH. Based on these findings, a preoperative diagnosis of secretory carcinoma was made, and the parotid gland lesion was treated by excision. Postoperative histopathology confirmed the diagnosis of secretory carcinoma.

The detection of the fusion gene ETV6-NTRK3 by RT-PCR or FISH plays an important role as a genetic marker for diagnosing this tumor, and FISH analysis of cell block specimens, in addition to HE staining, PAS staining, and immunostaining, enabled confirmation of the diagnosis.