Immunohistochemical analysis of progesterone receptor and Ki-67 labeling index in astrocytic tumors.

Abstract

Intracranial tumors such as meningiomas express steroid hormone receptors but little is known regarding progesterone receptor (PR) in astrocytic tumors. The authors evaluated expression of PR in 86 astrocytic tumors in relation to tumor proliferative potential. Paraffin embedded tumor sections were stained with polyclonal antiprogesterone antibody by the peroxidase-antiperoxidase method and with monoclonal MIB-1-Ki-67 antibody by avidin-biotin complex immunohistochemistry. Sixty-three of the 86 astrocytic tumors (73%) showed positive PR immunoreactivity. PR expression was observed in 4 of 9 pilocytic astrocytomas, 13 of 24 Grade 2 astrocytomas, 15 of 20 anaplastic astrocytomas, and 31 of 33 glioblastomas. In addition to the tumor cells, cells of microvascular endothelial proliferation and the smooth muscle of tumor vessel walls were frequently PR positive. Glioblastomas had a significantly higher percentage of PR positive cells compared with anaplastic (P < 0.0008) and low grade (P < 0.0001) astrocytomas. Patients with PR positive astrocytomas were of an older age than patients with PR negative astrocytomas (48.71 +/- 21.95 years vs. 37.09 +/- 24.69 years; P < 0.04). The mean Ki-67 labeling index (LI) was significantly higher in the high grade (3-4) astrocytomas compared with low grade (1-2) astrocytomas (P < 0.0001). PR positive astrocytic tumors had higher Ki-67 LI than PR negative tumors. PR expression was not correlated with tumor recurrence and patient survival. The current study suggests that PR in the astrocytic tumors correlates with histologic grade and PR may participate in the growth of these tumors and tumor angiogenesis. The measurement of PR in these tumors may indirectly represent tumor growth potential.