Determination of the cell proliferation activity of
neoplasm is useful in making a prognosis. Immunohistochemical detection using
MIB-1 monoclonal antibody has recently allowed us to assess
tumor cell proliferation easily, because it can be performed on
paraffin-embedded specimens and the results have been demonstrated to be positively correlated with the results of
PCNA staining. In this study, surgical specimens of 63
pituitary adenomas were examined by immunohistochemical staining with
MIB-1 monoclonal antibody. Twenty-nine cases were non-functioning
pituitary adenomas, 20 were
prolactin (PRL)-producing
pituitary adenomas, and 14 were
growth hormone (GH)-producing
pituitary adenomas. The MIB-1 positive rates of the
pituitary adenomas ranged from 0% to 6.46%. In the non-functioning
pituitary adenomas, the MIB-1 positive rates ranged from 0% to 4.55% (mean : 0.76%), in the PRL-producing
pituitary adenomas the MIB-1 positive rates ranged 0% to 6.46% (mean : 0.91%), and in the GH-producing
pituitary adenomas the MIB-1 positive rates ranged 0% to 1.28% (mean: 0.58%). There were no significant differences between these values according to the results of the Wilcoxon signed-rank test. Although the size of the non-functioning
pituitary adenomas was not correlated with their MIB-1 positive rate,
tumor size was closely correlated with the interval between the onset of the initial symptoms and the date of surgery. In the PRL-producing
pituitary adenomas, the MIB-1 positive rate was not correlated with serum PRL levels as an index of secretory activity, but was correlated with the PRL staining positive rate. Preoperative
bromocriptine therapy proved effective in reducing
tumor size and serum PRL levels, but had no effect on the MIB-1 positive rate. In the GH-producing
pituitary adenomas, the MIB-1 positive rate was not correlated with serum GH levels as an index of secretory activity, but was closely correlated with the GH staining positive rate. All three groups included both invasive and noninvasive
tumor types, but there were no close statistical correlations between the three
tumor types.