The proliferative cell fraction in cytology specimens: A study of human esophageal carcinoma

Immunostaining of cell cycle-related antigens, especially Ki-67, DNA polymerase α, and proliferating cell nuclear antigen, has become an important method to assess the proliferative activity of tumors. These three nuclear antigens were studied by immunohistochemical analysis of cytologic smears. These smears were obtained by scraping the cut surface of 10 cases of esophageal squamous cell carcinoma and were fixed and prepared by different methods. The results were compared with those of tissue sections to apply the immunocytochemical findings of these antigens to cytology specimens. Smears that were placed on Denhardt- or Neoprene-coated slides and subsequently fixed in 4% paraformaldehyde and methanol exhibited the best cell adherence to the slides, had minimal loss of antigenicity, and had good preservation of cell morphologic features for all three antigens examined. The percentage of positive tumor cells in the cytology smear was generally in good agreement with that in the tissue section. For these three antigens, proliferating cell nuclear antigen demonstrated a much higher percentage of positive cells than either Ki-67 or DNA polymerase α, in both the smears and the tissue sections. In summary, Ki-67, DNA polymerase α, and proliferating cell nuclear antigen can be immunolocalized successfully in cytology smears and may become another parameter to assess the proliferative activity of tumors in the field of diagnostic pathology.