Anatomic mapping of acral melanocytic nevi and acral lentiginous melanomas among Taiwanese patients: A retrospective cohort study

Background: The early diagnosis of acral lentiginous melanoma (ALM) contributes to clinical outcomes since ALM can be mistaken for acral melanocytic nevus (AMN). ALM occurrence is reported to correlate with stress-bearing areas, which may assist in differential diagnoses. Our objective is to evaluate the distribution patterns of ALMs and AMNs on the palms and soles among Taiwanese patients. Methods: A retrospective analysis was performed by reviewing the charts of 1400 patients diagnosed with benign and malignant pigmented lesions confirmed after excisional biopsy at our institution between 2000 and 2022 in Taiwan. Correlations between lesions and clinicopathological factors were analyzed. Results: 309 AMNs and 177 ALMs were included. Mechanical stress was significantly associated with plantar ALMs (weight-bearing area: 92.65 %, arch: 7.35 %, P < 0.001). Significant differences in the distribution patterns were observed for plantar ALMs compared with all AMNs (P < 0.001) and non-atypical AMNs (P < 0.001), but were not observed between palmar AMNs and ALMs. Conclusion: Plantar ALMs were most commonly observed on the weight-bearing areas of the soles, distinct from the distribution of all AMNs and of non-atypical AMNs. The distribution features and anatomic mapping of ALMs may facilitate the early clinical diagnosis of ALM.