Proliferative activity in non-Hodgkin's lymphomas: A comparison of the Bromodeoxyuridine labeling index with PCNA immunostaining and quantitative image analysis

Cellular proliferation is being evaluated as an independent prognostic indicator in a variety of tumors, including non-Hodgkin's lymphomas (NHL). Although the labeling index (LI), using either tritiated thymidine or monoclonal antibodies to bromodeoxyuridine, is considered to be the gold standard of cell kinetic measurements, recent advances in the use of antibodies specific to cellular proliferating antigens and computer-based image analysis have potentially established a new technology for evaluating the growth fraction of NHL. Proliferating cell nuclear antigen (PCNA), a protein associated with DNA polymerase that is expressed only in the nuclei of cells actively synthesizing DNA, was quantitated in 46 formalin-fixed, paraffin-embedded samples of various types of NHL using the Cell Analysis Systems 200 image analyzer. The results were expressed as the percentage of nuclear area (%NA) positive for PCNA. These results were compared with the bromodeoxyuridine LI, and a correlation coefficient of 0.78 was calculated using first-order linear regression. An average positive NA of 8.2% for low- grade NHL, 32% for intermediate-grade, and 43% for high-grade NHL was observed. The potential advantages PCNA quantitation by image analysis may offer over LI are discussed.