High-grade non-intestinal type sinonasal adenocarcinoma with ETV6::NTRK3 fusion, distinct from secretory carcinoma by immunoprofile and morphology

We report 2 cases of high-grade sinonasal adenocarcinoma with a distinct morphological and immunohistochemical phenotype. Albeit histologically different from secretory carcinoma of the salivary glands, both tumors presented here share an ETV6::NTRK3 fusion. The highly cellular tumors were composed of solid and dense cribriform nests, often with comedo-like necroses in the center, and minor areas with papillary, microcystic, and trabecular formations without secretions, mostly located at the periphery of the lesion. The cells displayed high-grade features, with enlarged, crowded, and often vesicular nuclei with conspicuous nucleoli and brisk mitotic activity. The tumor cells were immunonegative for mammaglobin while showing immunopositivity for p40/p63, S100, SOX10, and GATA3, as well as for cytokeratins 7, 18, and 19. For the first time, we describe 2 cases of primary high-grade non-intestinal type adenocarcinomas of the nasal cavity, distinct from secretory carcinoma by morphology and immunoprofile, harboring the ETV6::NTRK3 fusion.

Automated summary

We present 2 cases of high-grade sinonasal adenocarcinoma with a unique morphological and immunohistochemical phenotype. Despite being histologically different from secretory carcinoma, both tumors harbor an ETV6::NTRK3 fusion. The tumors consisted of solid and dense cribriform nests with central comedo-like necroses, and peripheral areas with papillary, microcystic, and trabecular formations. The tumor cells showed high-grade features with enlarged nuclei, conspicuous nucleoli, and brisk mitotic activity. Immunohistochemical analysis revealed immunonegativity for mammaglobin but immunopositivity for p40/p63, S100, SOX10, GATA3, and cytokeratins 7, 18, and 19. These cases describe primary high-grade non-intestinal type adenocarcinomas of the nasal cavity with distinct morphology and immunoprofile, characterized by the ETV6::NTRK3 fusion.