Introduction In a Belgian population of cutaneous malignant melanoma (MM) patients, we examined the association of known risk factors for MM with site distribution, histological subtype and number of primary melanomas.
Methods Four hundred and twelve melanoma patients, who attended the Department of Dermatology at the University Hospitals Leuven (Belgium) between 2004 and 2009, were included in the study. Data on demographic factors, such as age and gender, and known risk factors for MM, including phototype, number and site of highest distribution of common naevi as well as atypical naevi, skin photodamage and family history of melanoma were obtained through personal interview and physical examination. Correlation between the risk factors and body site, histological subtype and primary melanoma count were analyzed by calculating the odds ratios (OR) and 95% confidence intervals (95% CI) using logistic regression analysis.
Results MM on the head and neck increases with age (3.6% each year), is more frequent in males (OR=3.5, CI: 1.9–6.7) and less likely to develop in people with atypical naevi (OR=0.4, CI: 0.2–0.9). Truncal melanoma decreases with age (3.3% each year), is also more likely in males (OR=2.3, CI: 1.4–3.8) and in patients who have the highest common naevi density situated on the back (OR=2.1, CI: 1.3–3.5). Melanoma on the lower extremities is more typical for females (OR=4.4, CI: 2.5–7.6) and in those with the highest common naevi concentration on the lower extremities (OR=1.7, CI: 1.02–3.0). Superficial spreading malignant melanoma decreases with age (3% each year), is more likely to occur among females (OR=2.4, CI: 1.4–4.1) and in patients who have atypical naevi (OR=3.4, CI: 1.6–7.3). Nodular melanoma is more common in males (OR=5.2, CI: 2.2–12.3) and is less likely to develop in patients with atypical naevi (OR=0.3, CI: 0.1–0.9). Lentigo maligna melanoma incidence increases with age (8,6% each year). Occurence of more than one primary MM is correlated with low skin type (I vs. other skin types) (OR=4.7, CI: 2.2–10.1) and presence of atypical naevi (OR=3.7, CI: 1.8–7.8).
Conclusion Data indicate that in a Flemish population of MM patients, a preferential link exists between MM site and local concentration of common naevi, age and gender. Specific histological subtypes are correlated with age, gender and presence of atypical naevi while multiple primary melanomas develop preferentially in patients with low skin type and atypical naevi. These findings support the existence of more than one pathway towards melanoma.