Other genes with frequent mutations in introns included PTPRD (14 mutations in 9 samples), which also frequently had mutations in the coding region; NOTCH2 (6 mutations, including 2 splice-site mutations in 6 samples), which also frequently had mutations in the coding region; ERBB4 (6 mutations in 6 samples), a well-known oncogene playing a role in many cancers [reviewed in (98)]; and DROSHA (5 mutations in 5 samples), which encodes a core enzyme (nuclease) of the miRNA processing pathway and has been shown to be upregulated in BCC (99). This evidence concerns the gene NOTCH2 and skin basal cell carcinoma.