Demographic and socioeconomic patterns of malignant melanoma in junctional nevus: An NCDB analysis.

e21572 Background: Malignant melanoma in junctional nevus (MMJN) is a rare type of cutaneous melanoma that originates in melanocytes located at the dermoepidermal junction. Although uncommon, malignant transformation in a junctional nevus is aggressive, with documented cases progressing to parotid and cervical lymph nodes as well as distant sites. Nevus-associated melanomas, including those arising in junctional nevi, have shown better overall prognosis independent of sentinel lymph node status. Due to MMJN being grouped with broader melanoma categories, we conducted a large-scale analysis of the NCDB to clarify demographic and socioeconomic factors influencing diagnosis and outcomes. Methods: A retrospective cohort analysis using NCDB data (2004–2020) was performed to evaluate demographic and socioeconomic characteristics of patients with MMJN (ICD-O-3 code 8740/3). Variables included age, sex, race, Hispanic origin, income, insurance, facility type, region, tumor features, surgical procedures, primary site, treatment, and Charlson-Deyo comorbidity score. Incidence trends were analyzed using descriptive statistics. Results: A total of 612 patients were identified with a stable incident trend over the study period (R²=0.18). Most were male (56.7%), White (97.5%), and non-Hispanic (93.0%), and had a mean age at diagnosis of 56.14 years (SD=16.83). The largest proportion were treated at academic/research programs (43.7%), in the Pacific region (35.0%), and lived in metro areas ≥250k population (78.8%). Private insurance (66.3%) and Medicare (27.1%) were most common. Nearly half lived in the highest income quartile (49.2%), and the mean travel distance was 32.4 miles. The trunk (37.8%) and lower limb/shoulder (25.4%) were the most frequent anatomical sites. Most tumors were Stage 0 (23.5%) or Stage I (28.4%); Stage II–IV disease were rare. The mean tumor size was 18.37 mm. Most patients had a Charlson–Deyo score of 0 (91.2%). Survival beyond thirty days (98.8%) and ninety days (98.5%) was high. Wide local excision (26.3%) and wide excision with sentinel node biopsy (24.5%) were the most common procedures. Few received radiation (1.5%), chemotherapy (0.5%), or immunotherapy (0.8%). Survival rates were 96.5% at two years, 92.0% at five years, and 78.1% at ten years. Conclusions: To our knowledge, this is the first NCDB analysis focused on MMJN, addressing a major gap in the literature on this rare neoplasm. Consistent with prior case studies describing nevus-associated melanoma, most patients were non-Hispanic, White, and presented with early-stage disease. This study also provides the first large-scale evaluation of socioeconomic characteristics, showing that most lived in higher-income metro regions and received care at academic centers. Further research is needed to determine how these demographic and socioeconomic patterns impact detection, treatment decisions, and long-term survival.