Proliferation of invasive breast carcinomas and colorectal adenocarcinomas: an immunohistochemical in situ investigation with the monoclonal antibody Ki-67.

The proliferation rates of 46 invasive breast cancers and of 22 invasive adenocarcinomas of the large intestine were determined immunohistochemically using the monoclonal antibody Ki-67. According to Gerdes et al., Ki-67 reacts with a nuclear-associated antigen selectively expressed in proliferating cells. The maximum number of Ki-67+ tumour cells was calculated in each case. Statistical analysis revealed that the number of proliferating tumour cells was significantly higher in colorectal tumours than in breast cancers (p less than 0.001). Furthermore, age dependency of the proliferation rate was observed for breast cancers. Tumours of females less than or equal to 50 years old showed a significantly higher number of proliferating cells than did tumours of patients greater than 50 years old (p less than 0.05). The maximum number of proliferating cells was not found to correlate with the tumour stage or node status in either type of malignancy. The immunohistochemical findings correspond well to results of studies of tumour cell kinetics in breast cancer and colorectal carcinoma using the tritiated thymidine labelling index (3HTLI). Thus, the application of Ki-67 obviously not only enables a detailed in situ study of proliferating cells in human cancer but also might partially substitute the expensive and time-consuming determination of the 3HTLI as a prognostic tumour marker.