[Significance of p53 protein expression and proliferative potential with MIB-1 on tumor recurrence of pituitary...

Total or subtotal removal on initial surgery was carried out in 103 cases of pituitary adenomas and followed up for more than 5 years in 97 cases. 22 (21%) of 103 cases had tumor recurrence after the initial surgery. The p53 protein (DO-7, Novocastra Lab.) expression and proliferative potential with MIB-1 monoclonal antibody (MBL Co.) were evaluated in the non-recurrent and recurrent pituitary adenomas. Tissue samples were embedded in paraffin after fixation in 10% formalin and 3 microns sections were activated by microwave heating before being immersed with the antibodies. The positivities of the immunostaining for p53 protein and MIB-1 were calculated as % values of tumor cell nuclei stained to 1000 tumor cell nuclei in several fields. Most of the recurrent pituitary adenomas were large macroadenomas with suprasellar extension. However, tumor recurrence was not correlated with tumor type in terms of the hormonal secretion, surgical approach, and radiotherapy. 15 cases of the non-recurrent group had values of 1.0 +/- 0.5% (mean +/- SD) for their MIB-1 positive nuclei, whereas 18 cases of the recurrent group had high values of 2.5 +/- 1.2%. A statistically significant difference was observed between the two groups. 11 of the 18 cases of recurrent pituitary adenomas revealed high values of MIB-1 in excess of 2.0%. p53 protein was not found in 21 cases of the non-recurrent group. However, 5 (28%) of the 18 cases of recurrent pituitary adenomas demonstrated p53 protein expression with positive nuclei staining at lower than 1.0%. It is concluded that evaluations of the p53 protein expression and proliferative potential with MIB-1 represent important factors in predicting tumor recurrence of pituitary adenomas.