Acral lentiginous melanoma (ALM), is the most common form of melanoma in Japanese patients, and accounts for approximately 50% of all melanoma cases1). Among 
ALM, the lesions on foot sole is most frequent, followed by the lower nail lesions2).
    On the other hand, the occurrence frequency of malignant melanoma in the palm is relatively low (10%) 3), thus suggesting that cases with palmer ALM are rare, and that 
there may be different etiology between palmar melanoma and planter melanoma. Although characteristic genetic alterations are detected in melanomas according to their involved areas, BRAF or NRAS are not frequently found in ALM, and no previous studies have been reported characteristic genetic alteration of palmar melanoma. 
    Accordingly, we supposed that factors other than genetic abnormality were involved in the etiology of palmar ALM.

The association between mechanical stress and malignant melanoma on the palm and fingers