We first analyzed the genomic profile of cutaneous type adult T-cell leukemia/lymphoma (ATLL) in an attempt to clarify its clinical and biological characteristics. Genomic gains of 1p, 7q and 18q and loss of 13q were frequently detected. Gain of 1p36.33-32 or loss of 13q33.1-3 indicated poor prognosis. Among cases with generalized lesions, erythema/papule or nodule/tumor cases showed a distinct genomic profile, indicating that these 2 groups were biologically different and developed via different genetic pathways. Furthermore, cases with generalized nodule/tumor lesions tended to progress to aggressive ATLL.