Characteristics and survival of patients with invasive amelanotic melanoma in the USA.

Amelanotic melanoma (AM) has not been well characterized on a population-based level. Using cross-sectional, prospective data from 18 Surveillance, Epidemiology, and End Results registries, we carried out χ(2)-tests to compare characteristics of patients with AM with characteristics of patients with melanotic melanoma (MM), the Kaplan-Meier method to calculate 5-year survival among patients with AM and MM by stage, and competing risks regression to generate subdistribution hazard ratios for patients with AM using age, sex, and stage as predictors. We identified 628 cases of AM and 157,524 cases of MM. Patients with AM were more often male and older than patients with MM (P = 0.011 and P < 0.001, respectively). AM was more common on the face/ears compared with MM and less common on the trunk (P = 0.004 and P < 0.001, respectively). Ulceration was over three times more common among patients with AM than among patients with MM (38.0 vs. 12.5%, P < 0.001), and it remained more common among patients with AM even when stratified by Breslow depths of up to 2 mm (P < 0.001). Patients with AM were over three times more likely than patients with MM to have distant disease at diagnosis (10.0 vs. 2.9%, P < 0.001). Five-year melanoma-specific survival was significantly lower in patients with AM than in patients with MM (72.3 vs. 91.1%, P < 0.001). In competing risks regression, only stage was a significant predictor of melanoma-specific death. Our results demonstrate that the demographics of patients with AM and MM differ. AM is more advanced at diagnosis and is often more lethal than MM. Understanding the epidemiology of AM may help identify patients at highest risk and improve strategies for early detection.