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Analyses of proliferative potential in schwannomas
1Department of Pathology, Fujita Health University, School of Medicine, Toyoake, Aichi, Japan. masabe@fujita-hu.ac.jp
Brain Tumor Pathology
|September 12, 2000
Summary
High MIB-1 cell positivity in schwannomas may indicate degeneration, not malignancy. DNA topoisomerase IIalpha (topo-II) staining helps differentiate true proliferation from false positives in these tumors.
Area of Science:
- Neuro-oncology
- Surgical Pathology
- Immunohistochemistry
Background:
- Schwannomas are common nerve sheath tumors.
- MIB-1 (Ki-67) is a proliferation marker used in tumor assessment.
- High MIB-1 positivity in schwannomas can be challenging to interpret.
Observation:
- Thirty-eight schwannoma specimens were analyzed.
- Nine cases showed MIB-1 positivity index (PI) of 5% or more.
- Six of these cases exhibited localized MIB-1 positivity near Antoni type A/B borders, associated with CD68+ macrophages and apoptosis.
Findings:
- Three cases with high MIB-1 PI (>5%) were cellular schwannomas with mitotic figures, indicating malignancy.
- The other six cases with MIB-1 PI 5-8.41% showed degenerative changes, not overt malignancy.
- DNA topoisomerase IIalpha (topo-II) staining revealed low PI (0.78-1.93%) in these six cases, suggesting MIB-1 reactivity was due to cell cycle abnormalities from degeneration/apoptosis, not true proliferation.
Implications:
- High MIB-1 PI in schwannomas can be a false positive, particularly in areas with degeneration and apoptosis.
- DNA topoisomerase IIalpha (topo-II) staining is a valuable adjunct for accurate assessment of schwannoma proliferation.
- Distinguishing true proliferation from degenerative MIB-1 staining is crucial for appropriate clinical management.