Comprehensive mapping of all reported RAC1 mutations to date (from TCGA, AACR Project GENIE, COSMIC, and metastatic cancer data combined; www.cbioportal) reveals RAC1-A159V as a hotspot mutation mainly enriched in HNSCC (but also found in colorectal, cervical, and several other cancers, yet never in melanoma), while RAC1-P29S is a melanoma-prevalent mutation, which is also found in HNSCC and other cancers (Figure 1E, Supplementary Table S3). Here, RAC1 is linked to metastatic malignant neoplasm.