SMARCB1 and small cell carcinoma: Quite often, SMARCB1-deficient sinonasal carcinoma presents as small blue round cell tumors which mimic other sinonasal malignancies including undifferentiated carcinoma, NUT sinonasal carcinoma, lymphoma, small cell carcinoma, olfactory neuroblastoma, melanoma, and rhabdomyosarcoma.