Immunohistochemical evaluation of proliferative activity (Ki-67 index) in different histological types of cutaneous basal cell carcinoma

Evaluation of tumor cell proliferation status belongs to the basic prognostic indicators in a routine biopsy report. In cutaneous basal cell carcinoma (BCC), however, there are discrepancies about a true prognostic significance of this histopathological parameter. The aim of this study was to assess a proliferative activity (Ki-67 index) in BCCs of the skin. Biopsy specimens from 80 cutaneous BCCs (63 primary, 17 recurrent) of different histological types from 75 subjects (34 men, 41 women) were enrolled into this study. All samples were immunohistochemically stained by antibody against Ki-67 antigen (DAKO, clone MIB-1, dilution 1:100). For the statistical analysis, χ 2 test was employed. We found a striking percentage variability of nuclear Ki-67 expression in individual tumors (range 2–70%). Mean value of Ki-67 index was 27.4% (in primary tumors 28.1 %, in recurrent lesions 25.6%). The highest Ki-67 expression occurred in infiltrative BCCs (average 38.1%), morpheaform BCCs (average 37.0%), and superficial BCCs (average 35.7%), the lowest expression was recorded in nodular BCCs (average 21.7%) and BCCs with adnexal (trichoepithelial) differentiation (18.6%). There were not persuasive and statistically significant quantitative differences in proliferation activity of tumor cells between the individual histological BCC types, as well as between primary and recurrent lesions. A distribution of Ki-67 positive cells in tumor nests was mostly irregular and areas with a high number of Ki-67 labeled cells often occurred adjacent to areas with a lower number of cells expressing this marker. Because of a marked Ki-67 staining variability, we can conclude that the simple quantification of BCC proliferation activity alone may not be sufficient for the prediction of further biological behavior, evolution and clinical outcome of this malignancy.