Effect of anatomical site on prognosis and progression pattern in early-stage acral melanoma: A retrospective cohort study of 281 cases.

Abstract

The evolution of human bipedalism has led to distinct functional roles for the lower and upper limbs. In acral lentiginous melanoma (ALM), the factors influencing the first site of metastasis (whether lymphatic or systemic) remain unclear. This study aimed to compare the prognosis and metastatic progression patterns of upper versus lower-limb ALM. Patients with early-stage ALM whose exact location of the tumor was documented were retrospectively analyzed. First lymph node metastasis was significantly more frequent in lower-limb ALM, while first distant metastasis was more common in upper-limb ALM. This pattern was more evident in stage II ALM and nail unit melanomas compared to non-nail unit acral melanomas. Cox proportional hazards regression identified upper-limb location, ulceration, Breslow thickness, and lymphovascular invasion as independent predictors of systemic metastasis-free survival. For lymph node progression-free survival, only Breslow thickness and bone involvement were identified as independent prognostic factors. This was a retrospective study performed at a tertiary referral center. Lower-limb ALM, especially toenail melanoma was associated with first lymph node metastasis, while upper-limb ALM was significantly related to first distant metastasis, implying necessity of tailored surveillance strategies in early-stage ALM.