The ETV6-RET Gene Fusion Is Found in ETV6-rearranged Low-grade Sinonasal Adenocarcinoma Without NTRK3 Involvement
Abstract
Recently, a novel translocation-associated carcinoma restricted to the sinonasal tract, the ETV6-rearranged low-grade sinonasal adenocarcinoma (SNAC) was reported. This entity is morphologically and immunohistochemically different from secretory carcinoma (SC) of the salivary glands, but harbours an identical fusion between exon 5 of ETV6 and exon 15 of NTRK3.
Herein, we report an unique case of ETV6-RET low-grade SNAC occurring in 32-year-old female. The tumor originated in the maxillary sinus and extended into the middle meatus.
Microscopically, the tumor was tubular with focal cystic change, and consisted of cuboidal to cylindrical cells with bright, eosinophilic cytoplasm. Immunohistochemically, the tumor cells were diffusely positive for CK7, GCDFP-15, SOX10, and vimentin, and negative for CK20, GATA3, and mammaglobin.
As seems to be characteristic for ETV6-rearranged low-grade SNAC, DOG-1 was positive, and S-100 showed patchy expression. Fluorescence in situ hybridization demonstrated split signals for the ETV6 as well as RET probes, but intact NTRK3 signals.
The next-generation sequencing panel confirmed an in-frame fusion between exon 6 of ETV6 and exon 12 of RET with 80 fusion-spanning reads. Our identification of the ETV6-RET gene fusion in ETV6-rearranged low-grade SNAC is intriguing, as it further strengthens the genetic ties between this tumor entity and SC.
The significance of separating the morphologically different, but genetically identical ETV6-rearranged low-grade SNAC and sinonasal SC, awaits reports of clinical outcomes in larger series of both tumor types.