Melanomas at the acral location lead to poor survival, which may be partly because acral lentiginous melanoma, a distinct melanoma subtype, has a distinct biological profile and foul clinical behavior. However, since almost 50% of acral melanomas are not of the acral lentiginous melanoma subtype, the worse clinical behavior could also be due to the intrinsic features of the location.

A recent retrospective, observational study investigated if melanomas of the lower limb excluding acral lentiginous melanoma differ by location. 

Two hundred eighty-five patients with superficial spreading and nodular melanomas of the lower limb were included in the study. Melanomas were compared by site, clinical and pathological characteristics, and the differences by location of disease-free and melanoma-specific survival by the Kaplan-Meier method and Cox proportional hazard method. 

The results showed that the patients with melanomas on the foot, compared to those on the rest of the limb, were older and reported having suffered fewer sunburns; the melanoma more frequently emerged in rarely sun-exposed areas, was more frequently of nodular type, showed thicker tumors, with more ulceration, less regression, and more advanced stage of the disease. Foot location was associated with an increased risk of relapse and decreased melanoma-specific survival. 

Thus, it was concluded that melanoma development in the foot is less because of sun exposure and shows pathological features, which can worsen prognosis and cause poorer survival.

Source: Gavillero A, García-Casado Z, Requena C, et al. Differences by anatomical site of non-acral lentiginous melanomas of the lower limb. Dermatology 2022 Mar 29:1-9.