AICDA and cutaneous melanoma: Clusters 1 and 4 are specific to skin melanomas (MELA) and B cell malignant lymphomas (MALY) respectively, displaying characteristic origin signatures highly similar to the known signatures SBS7b (cosine similarity = 0.83, exposure to ultraviolet light) and SBS84 (cosine similarity = 0.88, activity of activation-induced cytidine deaminase (AICDA or AID)).