Anatomical distribution of basal cell carcinoma in Israel using relative tumor density scores

Background: Ultraviolet radiation (UVR) is considered a major risk factor for the development of basal cell carcinoma (BCC). Calculating the relative tumor density (RTD) by adjusting the proportion of BCC lesions relative to the skin surface area at a specific site enables comparison of the proportion of tumors at different anatomical sites and better understanding of the association with sun exposure. Objectives: To characterize anatomical distribution of BCC in the Israeli population using RTD score. Methods: A retrospective, cross-sectional study that includes all histologically confirmed BCC samples obtained from a major national pathological institute, which receives specimens from numerous surgeons throughout Israel, during the first trimester of 2012. Results: A total of 1,712 skin lesions were diagnosed as BCC during the study period. RTD in the head and neck area was the highest over the body (RTD = 6.6). We found that RTD over the upper arms in males was higher than the proportion of skin surface area (RTD = 1.1). A comparison of RTD values in subsites of the head and neck region indicates that men have higher RTD values for the ears, neck, and scalp than women. However, the nose and eyes areas have female predominance. Conclusions: Using RTD scores, our study demonstrates the unique UVR exposure pattern in the Mediterranean climate of Israel and supports the notion that UVR is an important risk factor for the development of BCC lesions.