Benign acral lesions showing parallel ridge pattern on dermoscopy


Miki Tanioka, M.D., Ph.D., Department of Dermatology, Graduate School of Medicine, Kyoto University, Shogoin, Sakyo-ku, Kyoto 606-8507, Japan. Email:


One of the recent advances in dermoscopy is the significance of parallel ridge pattern (PRP), which has 99% specificity in detecting both melanoma in situ and advanced melanoma on the acral volar skin. This review features exceptionally benign acral lesions showing PRP on dermoscopy. These benign lesions can be distinguished from malignant melanoma, because of the typical clinical history and associated symptoms. However, it is sometimes difficult for dermatologists to exclude malignant melanoma and a subsequent skin biopsy should be strongly recommended. These benign lesions include pigmentation due to a dye such as para-phenylenediamine, acral pigmented macules associated with Peutz–Jeghers syndrome, anti-cancer drug-induced hyperpigmentation on the volar skin, acral subcorneal hemorrhage and pigmented warts.