RB1 and head and neck squamous cell carcinoma: In addition, RB1 somatic mutations have been reported to be frequent in the SCLCs (up to 98%) [10, 38, 40] but were found to be rare in the HPV‐positive UCSCCs analyzed here (0%), and in previously reported HPV‐positive cervical adeno‐ and squamous cell carcinomas (7%) or HPV‐positive head and neck squamous cell carcinomas (3%) [36, 37] (Fig. 4A).