PROLIFERATING CELL NUCLEAR ANTIGEN AND KI-67 IMMUNOHISTOCHEMISTRY IN BRAIN-TUMORS - A COMPARATIVE-STUDY

Proliferating cell nuclear antigen (PCNA) is a 36-kDa DNA polymerase-partial derivative auxiliary protein which accumulates in the nucleus during S phase of the cell cycle. Immunohistochemical labeling indices (LI) of PCNA and Ki-67 were compared using an avidin-biotin complex method on frozen sections of 27 nervous system tumors, 3 normal cerebral cortices, and 3 peripheral nerves. In glial tumors, PCNA and Ki-67 LI increased with increasing tumor grade (Daumas-Duport system). In 5 low-grade glial tumors, PCNA and Ki-67 LI were less-than-or-equal-to 1%, except for one optic nerve glioma (Ki-67 LI = 6%). In 7 grade 3 astrocytomas and 1 mixed glioma, PCNA LI were less-than-or-equal-to 1-1.5%, while Ki-67 LI were 2%-10%. In 7 grade 4 astrocytomas and 1 metastatic carcinoma, PCNA LI ranged from 6%-15% while Ki-67 LI ranged from 17%-30%. In 5 of 6 schwannomas, focally high PCNA LI (4%-65%) were noted, despite low LI with Ki-67 (less-than-or-equal-to 1.6%). Scattered normal schwann cell nuclei also stained with PCNA, but normal cerebral cortex did not. These data suggest that: (1) in higher-grade gliomas, PCNA may be more specific S-phase marker, although a less sensitive proliferation marker, than Ki-67; (2) PCNA LI do not distinguish low-grade gliomas from grade 3 astrocytomas; (3) in schwannomas, PCNA may not reflect proliferative activity since it seems to react with an epitope present in normal schwann cells; and (4) the variable PCNA staining pattern introduces greater difficulties in cell counting than with Ki-67. These factors may limit the use of this anti-PCNA antibody in evaluating nervous system tumors.