A 50-year-old Japanese female of acral lentiginous melanoma in situ involved into deeper eccrine duct epithelium on the right middle finger was described. Histopathologically, increased number of atypical melanocytes were proliferated involving both lower epidermis and deeper portion, 643μm from epidermal basal layer, of eccrine sweat duct epithelium, which is a rare histological finding in usual ALM. It is well known and interesting that malignant melanoma in situ, especially ALM in situ often proliferate involving into superficial portion of eccrine duct epithelium, however, our case was exceptional.
We supposed that ALM in situ cells could proliferate with affinity to eccrine duct epitherlium. Taken together, we need careful treatment and follow-up for ALM in situ with proliferation into the deeper portion of eccrine duct as our case.