A Retrospective Single-institute Study Reveals a Vertical Gradient of the Density of Cutaneous Melanoma from Head to Toe

Background: The bodily distribution of melanoma is frequently reported without consideration of the skin surface area, which could be misleading in melanoma risk regarding anatomical sites.

Objectives: To gain insights into the melanoma distribution on the body surface when the body surface area is considered.

Methods: Cutaneous melanoma data were extracted from a single dermatopathology laboratory, and the relative density from each body site was calculated by taking into consideration the skin surface area. Data from a previous publication were analyzed as a validation. Surveillance, Epidemiology and End Results Program data were also used for comparison.

Results: Relative tumour density (RTD) of melanoma in men and women exhibits a moderate head-to-toe linear gradient, with the upper body sites showing higher density than the lower body sites in general. In particular, the ear and face show the highest RTD while the least UVR (ultraviolet radiation)-exposed buttock, abdomen and groin have the lowest, followed by the thigh and lower legs. The trend is similar in both sexes, but more obvious for men.

Conclusions: It was well documented that the trunk and lower legs are the most frequently diagnosed sites for men and women, respectively. However, when the surface area is considered, the melanoma distribution exhibits a rough head-to-toe gradient, which perhaps reflects a combined effect of solar UVR and clothing coverage. UVR protection on the face and ear should be emphasized as these are the sites with the highest RTDs.