Abstract: 【Abstract】 Objective To analyze potential roles of mechanical stress in the formation of plantar melanoma. Methods A retrospective analysis was conducted on 129 cases of plantar melanoma in Xiangya Hospital, Central South University between 2014 and 2021, and the distribution and clinical characteristics of plantar melanoma were analyzed. The goodness-of-fit test was used to compare the distribution of plantar melanoma between weight-bearing areas （the toes, forefoot, lateral midfoot, heel） and non-weight-bearing areas of the foot （the arch）, while t test, Fisher′s exact test and Wilcoxon rank sum test were used to analyze differences in clinicopathological characteristics of plantar melanoma between weight-bearing areas and non-weight-bearing areas of the foot. Results Among the 129 patients with plantar melanoma, 66 （51.2%） were males and 63 （48.8%） were females, and their age at onset was 60.6 ± 13.1 years. Plantar melanoma mostly occurred on the heel （65 lesions, 1.31 lesions per square centimeter）, followed by the forefoot （31 lesions, 0.41 lesions per square centimeter）, the bottom of the toes （15 lesions, 0.43 lesions per square centimeter）, lateral midfoot （11 lesions, 0.38 lesions per square centimeter） and the arch of foot （7 lesions, 0.16 lesions per square centimeter）. The goodness-of-fit test showed that melanoma was more prone to occur in the weight-bearing areas than in the non-weight-bearing areas （χ2 = 66.59, P < 0.001）; compared with the arch of foot, a higher incidence density was observed in the heel and forefoot （χ2 = 38.29, 5.23, P < 0.001, = 0.022, respectively）. There were no significant differences in the gender ratio, age and occupation of patients, prevalence rates of left/right foot involvement, Breslow thickness, ulceration status, Clark grades, lymph node metastasis rate, and stages between melanomas in the weight-bearing areas and those in non-weight-bearing areas （all P > 0.05）. Conclusion Plantar melanoma was more prone to occur in the weight-bearing areas than in the non-weight-bearing areas, suggesting that mechanical stress may be related to the occurrence and development of melanoma.

Key words: Melanoma, Mechanical stress, Clinicopathological characteristics