Epidemiology and demographic patterns of mucosal lentiginous melanoma: A retrospective NCDB cohort.

Abstract

e21608 Background: Mucosal lentiginous melanoma (MLM) arises from melanocytes in mucosal surfaces and is one of the rarest forms of melanoma, accounting for approximately 1–1.4% of all melanoma cases. It frequently follows an aggressive clinical course with poor long-term survival. Diagnosis is often delayed, and treatment guidance remains limited due to the scarcity of large studies. Broader epidemiologic data are needed to clarify its presentation and clinical context, prompting the use of the National Cancer Database (NCDB) to examine demographic patterns in patients with MLM. Methods: A retrospective cohort study using the 2004–2020 NCDB identified 330 patients with histologically confirmed MLM (ICD-O-3 Code 8746). Demographic variables included age, sex, race, Hispanic origin, facility type, urban status, income quartile, and Charlson-Deyo score. Treatment modalities and tumor characteristics were also analyzed. Descriptive statistics summarized patient features, and incidence trends were evaluated through regression analysis. Results: The incidence of MLM remained stable from 2004 to 2020 (R² = 0.515). Patients were primarily older adults (mean 64.9 years), female (71.8%), non-Hispanic (92.4%), and White (91.8%). Most had a Charlson-Deyo score of 0 (79.1%) and lived in metropolitan areas (85.3%), with 42.4% in the highest income quartile. The vulva (26.7%) and perianal skin (12.4%) were the most common primary sites. Surgical resection was performed in 79.0% of cases, with 58.2% achieving negative margins. Radiation, immunotherapy, and chemotherapy were administered to 24.8%, 19.4%, and 12.5% of patients, respectively, while hormone therapy was rarely used (0.9%). Palliative care was uncommon, with 95.5% of patients not receiving symptom-directed interventions. Patients traveled a mean of 73.6 miles (SD = 161.5) for treatment, most commonly at academic/research programs (66.3%). Early mortality was low (0.8% at 30 days; 1.5% at 90 days). Tumors averaged 39.0 mm, and mean overall survival reached 78.7 months, with survival rates of 66.2% at two years, 44.7% at five years, and 28.2% at ten years. Conclusions: This NCDB study provides the first population-level characterization of MLM. It predominantly affects older, non-Hispanic White females most commonly arising on the vulva and perianal skin. Most patients underwent surgical resection, and over half achieved complete tumor removal, with low early mortality. Radiation and immunotherapy were the most frequently used treatments, while palliative care was uncommon. Socioeconomic findings revealed that patients were more likely to reside in metropolitan areas, belong to the highest income quartile, and receive care at academic centers. These results underscore the need for further investigation into how demographic, socioeconomic, and treatment-related factors contribute to variability in outcomes for this rare melanoma subtype.