SMARCB1(INI1)‐deficient sinonasal adenocarcinoma: Report of a case previously diagnosed as high‐grade non‐intestinal‐type sinonasal adenocarcinoma

SMARCB1(INI1)‐deficient sinonasal carcinoma is a recently recognized entity with wide histomorphologic spectrum. The classification of sinonasal adenocarcinoma (SNAC) is complex and yet to be redefined, especially the category of high‐grade non‐intestinal‐type SNAC. Recently SMARCB1(INI1)‐deficient SNACs with an unique oncocytoid/rhabdoid cytomorphology and variable degrees of glandular formation have been reported. Here we described a rare case of SMARCB1(INI1)‐deficient SNAC composed of mainly oncocytoid/rhabdoid cells with mixed solid and cribriform patterns. This case was originally diagnosed as non‐intestinal‐type SNAC and was reclassified due to complete loss expression of SMARCB1(INI1) by immunohistochemistry (IHC). The SMARCB1(INI1) stain provides a valuable tool for identification of this specific type of SNAC. We compared this case with other SNACs diagnosed in our department and reviewed relevant literature for this specific type of SNAC.