Cellular proliferation characteristics of basal cell carcinoma: relationship to clinical subtype and histopathology

This study investigates the proliferation characteristics of 81 primary basal cell carcinomas (BCC) using detection of the Ki-67 antigen by immunohistochemistry. The tumours were classified into distinct sub-types based on their histological growth pattern and differentiation status. The mean Ki-67 growth fraction was 0.293 and this was found to vary between the different growth patterns, with morpheic, infiltrating and superficial tumours showing the highest levels of proliferation at 0.373, 0.351 and 0.335, respectively; the nodular and micronodular growth patterns were significantly lower at 0.248 and 0.232, respectively. No overall association was seen between proliferation and differentiation status although certain histological growth patterns such as nodular showed a greater propensity to differentiate. Proliferation was related to tumour size, with larger lesions exhibiting higher growth fractions although this may have also been related to tumour subtype as infiltrating and morpheic tumours tended to present with larger tumour diameters. The spatial distribution of proliferating cells by Ki-67 labelling was not related to tumour subtype, differentiation or growth fraction. These studies have shown BCC to possess proliferative characteristics akin to other solid tumours commonly regarded as more rapidly dividing. There was an association between growth fraction and tumour subtype consistent with higher proliferation in the lesions considered to be more aggressive.