High-grade salivary gland carcinoma with the ETV6-NTRK3 gene fusion: A case report and literature review of secretory carcinoma with high-grade transformation.
Secretory carcinoma or mammary analog secretory carcinoma is an entity of salivary gland carcinoma that is characterized by the ETV6-NTRK3 gene fusion. Although it is generally considered to be a low-grade malignancy, some cases of secretory carcinoma with high-grade transformation (SCHG) have been reported. We herein describe a case of SCHG composed almost exclusively of the high-grade component. The patient presented with a growing mass in the buccal mucosa and underwent surgery. Tumor cells showing high-grade nuclear atypia were arranged in solid or cribriform nests with comedo-like necrosis. A differential diagnosis included high-grade salivary gland carcinoma, such as salivary duct carcinoma. Immunohistochemically, tumor cells were focally positive for S-100 and negative for mammaglobin and showed nuclear positivity for pan-Trk. A reverse transcription polymerase chain reaction assay showed that the tumor harbored the ETV6-NTRK3 gene fusion. A histological review of microscopic slides of the tumor did not reveal a typical secretory carcinoma component, except for a very focal area. We ultimately diagnosed this tumor as SCHG. This case underscores the importance of recognizing the histological spectrum of SCHG and the utility of pan-Trk immunohistochemistry to detect secretory carcinoma, which may be targeted by tyrosine kinase inhibitors.
['Asai|Satsuki|S|http://orcid.org/0000-0003-4800-4126', 'Sumiyoshi|Shinji|S|http://orcid.org/0000-0002-2292-4373', 'Yamada|Yosuke|Y|https://orcid.org/0000-0001-7952-2706', 'Tateya|Ichiro|I|', 'Nagao|Toshitaka|T|', 'Minamiguchi|Sachiko|S|', 'Haga|Hironori|H|http://orcid.org/0000-0003-4322-9561']
salivary gland carcinoma ETV6-NTRK3 secretory carcinoma high-grade transformation pan-Trk