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Increased microglia proliferation separates pilocytic astrocytomas from diffuse astrocytomas: a double labeling study
1Institute of Pathology, Department of Neuropathology, University of Würzburg, Josef-Schneider-Strasse 2, 97080 Würzburg, Germany. r.klein@mail.uni-wuerzburg.de
Abstract:
It is not known how many non-tumorous cells in gliomas contribute to the proliferation rate. We investigated the proliferative activity of microglia in an immunohistochemical double-labeling study of pilocytic astrocytomas and astrocytomas WHO grade II-IV using the antibodies MIB-1 (Ki67) as proliferation-marker and Ki-M1P (CD68) as microglia marker. We found the highest indices of proliferating microglia in pilocytic astrocytomas with an average rate of 32% (+/- 6.8) of all proliferating cells. In contrast, the proliferation indices of microglia were lowest in fibrillary astrocytomas with 8.6% (+/- 2.5) of all proliferating cells. In anaplastic astrocytomas and glioblastomas the percentage of proliferating microglia showed a slight increase to 8.8% (+/- 3.6) and 13.4% (+/- 8.7), respectively. We conclude that microglial cells in astrocytic brain tumors proliferate and show different proliferative activities at different grades of malignancy with the highest rates of proliferating microglia especially in pilocytic astrocytomas. Thus, the proliferation rate does not solely reflect the proliferation of tumor cells, but also of non-tumorous cells. This should be considered in particular when proliferation rates are used as a criterion for prognosis and grading of pilocytic astrocytomas.
Insights
Microglia, a type of non-tumorous cell, significantly contribute to proliferation rates in brain tumors like astrocytomas. Their proliferative activity varies by tumor grade, being highest in pilocytic astrocytomas.
Area of Science:
- Neuro-oncology
- Cellular biology
- Immunohistochemistry
Background:
- The contribution of non-tumorous cells to glioma proliferation rates is not well understood.
- Microglia are key immune cells in the brain and their role in tumor proliferation requires investigation.
Purpose of the Study:
- To investigate the proliferative activity of microglia in various grades of astrocytic brain tumors.
- To determine if microglial proliferation varies with tumor malignancy.
Main Methods:
- Immunohistochemical double-labeling using MIB-1 (Ki67) for proliferation and Ki-M1P (CD68) for microglia.
- Analysis of pilocytic astrocytomas and astrocytomas WHO grade II-IV.
Main Results:
- Highest microglial proliferation indices were observed in pilocytic astrocytomas (average 32%).
- Lowest microglial proliferation was found in fibrillary astrocytomas (average 8.6%).
- Proliferation rates in anaplastic astrocytomas and glioblastomas were 8.8% and 13.4%, respectively.
Conclusions:
- Microglial cells actively proliferate in astrocytic brain tumors.
- Microglial proliferative activity differs significantly across tumor grades, notably high in pilocytic astrocytomas.
- Proliferation rates in gliomas reflect both tumor and non-tumorous cell proliferation, impacting prognostic and grading criteria.