Risk of classic Kaposi sarcoma with residential exposure to volcanic and related soils in Sicily

Purpose: Before AIDS, endemic (African) Kaposi sarcoma (KS) was noted to occur in volcanic areas and was postulated to result from dirt chronically embedded in the skin of the lower extremities. The primary cause of all KS types is KS-associated herpesvirus (KSHV) infection, but cofactors contribute to the neoplasia. We investigated whether residential exposure to volcanic or related soils was associated with the risk of classic Kaposi sarcoma (cKS) in Sicily. Methods: Risk of incident cKS (N = 141) compared with population-based KSHV seropositive controls (N = 123) was estimated for residential exposure to four types of soil, categorized with maps from the European Soil Database and direct surveying. Questionnaire data provided covariates. Results: Residents in communities high in luvisols were approximately 2.7 times more likely to have cKS than those in communities with no luvisols. Risk was not specific for cKS on the limbs, but it was elevated approximately four- to five-fold with frequent bathing or tap water drinking in communities with high luvisols. Risk was unrelated to communities high in andosols, tephra, or clay soils. Conclusions: Iron and alumino-silicate clay, major components of luvisols, may increase cKS risk, but formal investigation and consideration of other soil types and exposures are needed