NOTCH1 and head and neck squamous cell carcinoma: Within tumors invading into submucosa or muscularis propria, most SCC cells (>80%) did not express ICN1 with or without NOTCH1 mutations6, 7; however, a small subset of SCC cells expressed ICN1 in the invasive tumor front (35.3% for HNSCC, n = 17; 37.0% for ESCC, n = 227) (Fig. 7a; Supplementary Fig. 6).