Cell proliferation in colorectal adenocarcinomas: Comparison between Ki-67immunostaining and bromodeoxyuridine uptake detected by immunohistochemistry and flow cytometry

We compared three different means of assaying tumor proliferative activity in 30 human colorectal adenocarcinomas labeled in vivo with bromodeoxyuridi ne (Br-dUrd). The labeling indices (LI) of BrdUrd obtained both by flow cyt ometry (FCM) and immunohistochemistry (TH) were also compared with the labe ling index of Ki-67. These methods were then related to tumor ploidy and pa thological features. Flow cytometry was performed in accordance with Begg's method after intrave nous infusion of BrdUrd four hours before surgery. Immunohistology was carr ied out on paraffin-embedded sections with monoclonal antibodies against Br dUrd and Ki-67. A positive correlation was found between BrdUrd LI obtained by both FMC and IH (p <0.0001), a finding that complies with the literature. However, we r eport on a correlation between Ki-67 LI and BrdUrd LIs in colorectal tumors (p=0.012). The results were valid for all tumors when they were subdivided into diploid and aneuploid groups. The labeling indices were significantly higher in the aneuploid turner group than in the diploid group (p=0.047). No relationship between proliferation parameters and tumor stage or grade w as found. To our knowledge, this is the first report on a positive correlation betwee n tumor proliferation indices in BrdUrd LIs and Ki-67 in colorectal carcino mas. This finding validates the value of Ki-67 immunostaining, which, howev er, should be confirmed in a larger series under the same technical conditi ons.