COMPARISON OF IMMUNOSTAININGS FOR PROLIFERATING CELL NUCLEAR ANTIGEN AND KI-67 IN HUMAN EXTRAOCULAR LESIONS

Background: Cell kinetic information is helpful to understand disease progression, treatment response, and prognosis of the neoplasms. To co mpare the usefulness and limitations of antibodies that recognize the cell cycle-associated molecules, proliferating cell nuclear antigen (P CNA) and Ki-67, we performed immunostaining in formalin-fixed, paraffi n-embedded tissue sections of extraocular lesions. Methods: Specimens were obtained from patients undergoing routine surgical procedures. Fo rmalin-fixed, paraffin-embedded sections were stained for PCNA and Ki- 67 using the monoclonal antibodies PC10 and MIB-1, respectively. Micro wave oven heating for antigen retrieval was performed before immunosta ining. Results: In squamous cell carcinomas and basal cell carcinomas, PCNA immunostaining varied greatly. Basal cells of benign epithelial lesions showed moderate to weak PCNA staining. Strong PCNA immunoreact ivity was demonstrated in foci of inflammation and germinal centers. M icrowave processing en hanced the intensity of those PCNA immunostaini ngs. As the PCNA immunostaining intensity had a great variability, the absolute numbers of PCNA-positive cells were hard to count in some ti ssues. High Ki-67 counts were observed in squamous cell carcinomas, fo ci of inflammatory cells, and germinal center cells. Basal cell carcin omas and benign lesions showed low Ki-67 counts. Every section showed clear nuclear staining in Ki-67 immunostaining. Conclusion: Careful co nsideration is required in the assessment of cell proliferation using PCNA. The immunostaining of Ki-67 may be more accurate than that of PC NA for evaluating cell proliferation in formalin-fixed, paraffin-embed ded tissues.