A case of "ETV6-FISH-negative" secretory carcinoma of the parotid gland: immunohistochemical study.

Secretory carcinoma of the salivary glands is a relatively new disease concept, and is characterized by "morphological resemblance to mammary secretory carcinoma and ETV6-NTRK3 gene fusion." Herein we describe a confusing case and briefly discuss practical diagnostic problems. The patient was a 71-year-old Japanese man who had a tumor consistent with secretory carcinoma at the microscopic and immunohistochemical levels. Immunohistochemically, EMA and S100 protein were noted to be positive along with various cytokeratins as well as mammaglobin and pSTAT5. Moreover, vimentin was focally positive. Smooth muscle actin, p63, p40, and androgen receptor were negative. However, a search using fluorescence in situ hybridization did not reveal a definite split signal for the ETV6 gene. It is presumed that confirming the diagnosis of secretory carcinoma without genetic retrieval will be accepted as a diagnostic method, and we hope that worldwide general recognition may earlier reach "gradual acceptance."