Figure. Ratios of Observed to Expected (O:E) Number of Skin Cancers by Body Site.

The O:E ratios with 95% CIs are reported for all cases combined and for the most common cancers by multiplying the total number of cases at all sites (excluding overlapping and unspecified sites) by the proportional body surface area (head and neck, 9%; trunk, 37%; upper extremities, 18%; and lower extremities, 36%). Body surface area estimates were derived from Wallace’s Rule of Nines.²⁷ We report P values from a χ² test assessing whether there is a global difference in the observed and expected counts across the 4 body sites.