Basal cell carcinoma of the skin: Topographic distribution and clinicopathological differences with regards to the extent of sunlight exposure

Objective To analyze a topographic distribution of cutaneous basal cell carcinoma (BCC) and clinicopathological differences of disease with regards to the extent of sunlight exposure. Methods A total of 1,065 BCC cases from 815 patients were investigated. The topographic regions of the body affected were merged into the sun-protected, intermittently sun-exposed, and permanently sun-exposed sites. Results BCCs occurred most commonly in the permanently sun-exposed sites (63.8%), followed by intermittently sun-exposed sites (30.8%), and sun-protected sites (5.4%). There was higher proportion of the men in the parts of the body intermittently exposed to sunlight and vice versa, higher percentage of the women in the sun-protected, as well as, in the permanently sun-exposed parts. There was a statistically significant trend towards an increased age with rising extent of sunlight exposure. Superficial BCC correlated positively with the intermittently sun-exposed sites and negatively with the permanently sun-exposed sites. Nodular BCC was related to the permanently sun-exposed sites and negatively with the intermittently sun-exposed sites. Infiltrative BCC was linked to permanently sun-exposed sites, while it was completely absent in the body regions, the skin of which was usually protected from UVR. A proportion of BCCs with aggressive growth phenotype positively correlated with rising extent of sunlight exposure. Conclusion Considerable clinicopathological variations in BCCs depending on locations and corresponding solar exposure levels were confirmed. With respect to the body sites, from which the lesions arise, this neoplasia may have distinct etiopathogenesis and biology. Probably, different patterns of sun exposure are independent risk factors for certain histological BCC subtypes and hence prognosis of this malignancy.