The diagnosis of a sinonasal undifferentiated carcinoma (SNUC) became a diagnosis of exclusion and must also be distinguished from an aggressive, poorly differentiated carcinoma with round blue cells and an abrupt keratinization NUT (NUclear protein in Testis) carcinoma, which can be diagnosed by at least diffuse nuclear staining of > 50% of tumor cells for a NUT protein [14,15] and a SMARCB1 (INI-1)-deficient sinonasal carcinoma or sinonasal neuroendocrine carcinoma (SNEC) [16,17,18]. Here, NUTM1 is linked to sinonasal undifferentiated carcinoma.