A study of proliferative markers in central neurocytoma.

To gain a better insight into the biological behavior of central neurocytomas, various proliferative indices were studied in these tumors and correlated with the histological features as well as the clinical outcome. Twenty cases of neurocytoma were selected over a 16 year period (1980-1995), which accounted for 0.28% of all intracranial tumors reported at this centre. Treatment consisted of surgical resection (total 14, subtotal six) followed by radiotherapy. Except for five patients who died of surgical complications, the remaining 15 were all alive and well during the follow-up period, varying from six months to 72 months (average 32 months). Thirteen tumors showed benign histological characteristics (Group I) while seven showed mitoses + necrosis (Group II). The proliferative index was assessed in formalin-fixed paraffin-embedded tissue of 17 cases using the silver nucleolar organiser region (AgNOR) technique and immunohistochemical staining for proliferating cell nuclear antigen (PCNA-PC10 antibody) and Ki-67 antigen (MIB-1 monoclonal antibody). The AgNOR counts ranged from 1.2 to 2.6 (mean 1.9 +/- 0.4), PCNA labeling index (LI) from 0.1 to 5.5 (mean 2.5 +/- 1.8) and MIB-1 LI from 0.1 to 3 (mean 0.8 +/- 0.02). There was no significant difference in any of these parameter values between histological Groups I and II, except that MIB-1 LI tended to be higher in Group II tumors. Further, there was no significant correlation between these proliferative indices and the mitotic rate of the tumors as well as the survival of the patients. A longer follow-up will be required to determine the relationship between proliferative markers and outcome as well as to bring out any heterogeneity in their biological behavior. Since these are relatively rare tumors, multicentric pooling of data will be required to reach a definitive consensus regarding their biological aggressiveness and consequentially, the use of radiotherapy in their treatment. The present report is a contribution in this direction.