Our cross-species analysis of human and canine melanomas is particularly important since canine patients are used as spontaneous models of human mucosal melanoma, and while we found many similarities, such as mutations in NRAS, TP53, and NF1, the genomes of canine melanomas lacked mutations in other key human mucosal melanoma drivers, such as SF3B1 and ATRX. Thus, dogs may not represent a faithful genetic model for these sub-types of human mucosal melanoma. Here, ATRX is linked to mucosal melanoma.