CLINICAL-FEATURES AND GROWTH FRACTIONS OF PITUITARY-ADENOMAS

BACKGROUND The Ki-67 monoclonal antibody is expressed by proliferating and dividing cells, but not by resting cells, The specificity of the monoclonal antibody, MIB-1, against the Ki-67 antigen has been establi shed by immunostaining of formalin-fixed paraffin-embedded tissue in a microwave oven. METHODS The growth fraction of 85 pituitary adenomas was studied retrospectively by immunohistochemical analysis using the monoclonal antibody MIB-1. The adenomas were classified into three typ es: microadenoma, expansive type, and invasive type, based on findings on Cd TPA enhanced magnetic resonance imaging. RESULTS The mean MIB-1 index in nonfunctioning microadenomas was higher than in expansive an d invasive adenomas, but this difference was not significant, The MIB- 1 index in younger patients (under 30 years) with nonfunctioning adeno mas was significantly higher than in patients over 40 years of age. On e of 14 patients with recurrent disease had an elevated MIB-1 index, b ut generally patients with an MIB-1 index over 2.0% did not suffer rec urrence, The mean MIB-1 index was higher in expansive and invasive fun ctioning adenomas than microadenomas, but not significantly. No correl ation between the MIB-1 index and the serum GH or PRL concentration wa s established. No MIB-1 positive nuclei were observed in two GH-produc ing adenomas treated with the somatostatin analog SMS 201-995. CONCLUS IONS No significant relationship was identified between growth fractio n and the invasiveness or recurrence of pituitary adenomas. The growth fraction of nonfunctioning pituitary adenomas was higher in patients under 30 years than over 40 years of age. (C) 1997 by Elsevier Science Inc.