Comparative Analysis of Ki-67 Protein as a Proliferative Expression Index in Cutaneous Basal and Squamous Cell Carcinoma in Federal Medical Centre Umuahia, Nigeria

Background: Evaluating the tumor proliferative index helps predict clinical behavior and provides prognostic insights for cutaneous basal cell carcinoma (cBCC) and squamous cell carcinoma (cSCC). Objective: This study aimed to identify differences in the proliferative indices among variants of cBCC and cSCC diagnosed at a tertiary healthcare center. Method: Skin biopsies histologically diagnosed as cBCC and cSCC between 2012 and 2018 at the Federal Medical Centre (FMC) Umuahia, Abia State, Nigeria, were analyzed. Archival formalin-fixed, paraffin-embedded (FFPE) tissue blocks were retrieved along with clinical data, and were prepared on charged microscope slides and the immunohistochemical staining was carried out. The primary antibody used in this study was clone BioCare CRM325C (RM) and adenotonsillar tissue blocks/slides served as positive controls. Ki-67 immunohistochemistry was performed on fresh 4μm sections of the tumor specimens. Results: The application of Ki-67 immunoperoxidase on both BCC and SCC cohort, yielded an intense observable brownish nuclear stain in areas of dense proliferating tumour cells on both cutaneous tumours. The average Ki-67 index for all cSCC cases was 24.7%, with a range of 2.3% - 80%, while the mean for cBCC was 15.8%, ranging from 1.2% - 45.6%. Variants with high proliferative indices were observed in 11.9% of cBCC cases and 29.1% of cSCC cases. Among the low proliferative index category, cSCC accounted for 5.4%, while cBCC represented 14.3%. For mild proliferative indices, cSCC cases made up 7.3% and cBCC, 11.9%. The majority of cases showed moderate proliferative indices, with 61.9% for cBCC and 58.2% for cSCC. Overall, there was a significant difference in proliferative indices between cSCC, cBCC, and their variants. Conclusion: The study found a significantly higher rate of cell proliferation, measured by Ki-67 immunostaining, in cSCC and its variants compared to cBCC. However, certain variants of cBCC also exhibited high Ki-67 expression, indicating they can be as aggressive as some cSCC variants.