The proliferating cell nuclear antigen index in breast carcinomas does not correlate with mitotic index and estrogen receptor immunoreactivity.

To investigate the expression of a marker of cell proliferation (PCNA/Cyclin) and its putative relationship with histological grading, mitotic index and estrogen receptor immunoreactivity, we studied twenty-seven cases of invasive breast carcinoma in formalin-fixed, paraffin-embedded tissue sections. The PCNA and estrogen receptor were detected by the PC 10 and H 222 monoclonal antibodies respectively, using an avidin-biotin-peroxidase method. The median value of PCNA index was 20.9% with a range from 1.4 to 84.2%. We did not find any significant relationship between PCNA index and the histological grading, mitotic index and estrogen receptor immunoreactivity. We conclude that PCNA detected by the monoclonal antibody PC 10 in formalin-fixed material looks at present unreliable as a proliferation marker in breast carcinoma.