Ki-67 expression of immunohistochemistry using computerized image analysis is a useful prognostic marker in follicular lymphomas

Ki-67 is a useful proliferation marker in various tumors including lymphoma. In general, the number of Ki-67 positive cells in immunohistochemistry (IHC) is counted manually for routine pathological diagnosis. However, a manual count is subjective and time consuming. Currently, image analysis is often used for the quantification of positive cells in tissue in IHC. Thus, to determine the pathological prognostic factors for follicular lymphoma (FL), we studied the relationship between Ki-67 expression in IHC and the treatment effect and prognosis using image analysis software. We analyzed 82 newly-diagnosed patients with FL. All patients were treated with rituximab-containing regimens. The median Ki-67 expression was 17.0%. A high expression of Ki-67 tended to be associated with short overall survival (P = 0.058). Moreover, Ki-67 expression was significantly lower in patients with FL grade 1-2 than in those with FL grade 3a. This study suggests that image analysis provides an accurate, reproducible, and easy method of measuring Ki-67 expression in IHC in FL, and is possibly a useful marker for treatment selection or prognosis prediction in FL.