Skin cancer arising in scars: a systematic review.

BACKGROUND Despite numerous case reports, epidemiologic evidence regarding true rate of skin cancer in scars of any etiology is sparse. METHODS Systematic literature review of all published epidemiologic studies on skin cancer in scar tissue from surgery, ulcers, or burns using citation databases and manual review. RESULTS There were no epidemiologic data to quantify risk of skin cancer in surgical scars or chronic ulcers. Two eligible cohort studies were identified, from Denmark and Sweden, in which skin cancers in 16, 903 and 37,095 burn patients, respectively, were ascertained through cancer registry follow-up. Each reported standardized incidence ratios (SIRs) for skin cancer types on any site that were uniformly less than unity compared with the general population. Only the Danish cohort assessed skin cancers specifically on past burn injury sites and found a burn-site-specific SIR of 1.2 (95% confidence interval (CI)=0.4-2.7) for squamous cell carcinoma (SCC), 0.7 (95% CI=0.4-1.1) for basal cell carcinoma, and 0.3 (95% CI=0.0-1.2) for melanoma. CONCLUSIONS Available epidemiologic data suggest that burn patients are not at higher risk of skin cancers in general, although a modest excess of SCC in burn scars cannot be excluded, nor can excess risk with longer follow-up. Risk of skin cancer in scars other than burn scars has not been investigated epidemiologically.