Epidemiology and histological spectrum of cutaneous melanoma in Sri Lanka: a population-based analysis, 2015–2022

Background: Cutaneous melanoma is a biologically aggressive malignancy demonstrating substantial geographic, ethnic, and environmental heterogeneity. Although melanoma incidence remains markedly lower in South Asia than in Western populations, demographic aging, improved cancer surveillance, and evolving dermatopathology infrastructure may progressively alter melanoma burden in low- and middle-income countries (LMICs). Population-level melanoma epidemiology from Sri Lanka remains limited.
Methods: A retrospective population-based epidemiological study was conducted using Sri Lanka National Cancer Registry data from 2015 to 2022. All cutaneous melanoma cases (ICD-10 C43) were included. Comparative analyses incorporated non-melanoma skin cancers (NMSC; ICD-10 C44) and overall malignant neoplasm incidence. Crude incidence rates, age-specific incidence rates, mortality rates, and age-standardised incidence rates (ASIRs) per 100,000 population were calculated using the WHO standard population methodology. Temporal trends were evaluated using annual percentage change (APC) analysis through log-linear regression. Mortality-to-incidence ratios (MIRs) were calculated as survival proxies. Histological subtype distributions and sex-specific differences were evaluated descriptively and analytically.
Results: Between 2015 and 2022, 760 melanoma cases were recorded nationally, including 396 males (52.1%) and 364 females (47.9%), producing a male: female ratio of 1.09:1. Annual melanoma incidence increased from 74 cases in 2015 to 117 cases in 2022, representing a 58.1% relative increase in crude case burden. Crude incidence ranged from 0.35–0.53 per 100,000 population, whereas ASIR remained relatively stable between 0.33–0.51 per 100,000 population. APC analysis demonstrated no statistically significant increase in ASIR (APC +0.41% annually; P=0.792). Incidence increased sharply after 50 years and peaked among individuals aged ≥75 years. Melanoma mortality demonstrated a gradual expansion with persistently elevated MIR values ranging approximately 0.36–0.44. Melanoma not otherwise specified (NOS) represented 81.9% of classified cases. Among specified subtypes, acral lentiginous melanoma and nodular melanoma predominated. NMSC incidence exceeded melanoma approximately sixfold and demonstrated statistically significant incidence acceleration (APC +5.31%; P=0.028).
Conclusion: Melanoma incidence in Sri Lanka remains substantially lower than in Western populations but demonstrates progressive absolute expansion associated predominantly with demographic ageing rather than substantial increase in melanoma risk. Persistent high MIR values and extensive NOS histological classification indicate ongoing diagnostic and pathological limitations. These findings support the emergence of an early melanoma epidemiological transition in Sri Lanka within the broader framework of LMIC cancer evolution.