Conclusions: We identified that that the partial loss (mosaic expression) of SMARCB1 in SNSCCs is associated with high-grade malignant characteristics and a negative effect on patient survival; meanwhile, SMARCA4-mosaic expression in SNSCCs is associated with high-grade malignant characteristics and an increase in tumor size concerning the intact SMARCA4. The gene discussed is SMARCB1; the disease is neoplasm.