356 Polypoid melanoma is associated with aggressive histopathological characteristics and poor clinical prognosis

Abstract

Polypoid melanoma is a rare subtype of melanoma characterized by pedunculated exophytic growth. These tumors tend to have a thick Breslow depth, but it is unknown if the prognosis of this subtype is worse compared to other variants of melanoma. A retrospective review was performed of 37 polypoid melanomas and compared to 264 non-polypoid nodular melanomas. Each case was independently re-evaluated by board-certified dermatopathologists for the following histopathologic parameters including Breslow depth, mitotic rate, ulceration, and angiolymphatic invasion. Basic demographic data and clinical characteristics were collected from electronic medical record data and compared, including clinical stage at diagnosis, rates of recurrence, and survival, between polypoid and nodular melanoma subtypes. Patients with polypoid melanoma had a younger average age than patients with nodular melanoma. Histopathologic review revealed that polypoid tumors had a significantly higher average Breslow depth, and had a higher frequency of ulceration and angiolymphatic invasion than nodular melanomas. Analysis of clinical outcomes by log-rank test showed a higher risk of distant recurrence and worse overall survival in polypoid tumors compared to nodular melanomas. Multivariate analysis showed an association of polypoid subtype with higher distant recurrence and worse survival. This association was independent of other prognostic factors including Breslow depth and ulceration. This study shows that polypoid melanoma is associated with a higher frequency of aggressive histopathological characteristics and poor clinical prognosis compared to non-polypoid nodular melanoma.