Pilomyxoid astrocytomas with rare rosenthal fibers
Xiaomei Ma1,2, Yin Wang3, Huimin Liu4
1Department of Pathology, Changzheng Hospital, Second Military Medical University, Shanghai, 200003, China. maxiaomei2001@126.com.
Abstract:
Pilomyxoid astrocytomas (PMAs) were first officially described in 2007. Since then, intermediate pilomyxoid tumors with histopathological features typical of both PMAs and pilocytic astrocytomas (PAs) have been described. However, we found evidence of tumors that are histologically like PMAs but contain rare Rosenthal fibers, which have been reported in PAs but not in PMAs. We retrospectively analyzed four such cases involving a 16-year-old adolescent with a 3-cm recurring suprasellar tumor, an 11-year-old boy with a nonrecurring 3-cm mass in the left cerebellum, an 18-year-old adolescent with a mass in the suprasellar cistern who died 2 days after total tumor resection, and a 26-year-old woman with a nonrecurring 2-cm mass in the right temporal lobe. Microscopically, the tumors were a monomorphous population of small bipolar cells in a prominent myxoid/mucoid background with rare Rosenthal fibers. The tumor cells infiltrated the adjacent brain parenchyma. Findings for glial fibrillary acidic protein and oligodendrocyte transcription factor were positive, and the Ki-67 protein proliferation index was about 2%. Our findings document the existence of tumors that are histologically like PMAs but also have Rosenthal fibers. Studies of more such cases are needed for clarification of such tumors' clinical features.
Insights
Pilomyxoid astrocytomas (PMAs) exhibiting rare Rosenthal fibers, typically associated with pilocytic astrocytomas (PAs), have been identified. Further research is needed to clarify the clinical features of these unique brain tumors.
Area of Science:
- Neuropathology
- Pediatric Oncology
- Molecular Diagnostics
Background:
- Pilomyxoid astrocytomas (PMAs) are a recognized entity since 2007.
- Intermediate tumors sharing features of PMAs and pilocytic astrocytomas (PAs) have been reported.
- Rosenthal fibers are characteristic of PAs, not previously observed in PMAs.
Observation:
- Retrospective analysis of four cases revealed tumors histologically similar to PMAs.
- These tumors contained rare Rosenthal fibers, a feature not typically seen in PMAs.
- Microscopic examination showed small bipolar cells in a myxoid background with infiltration of adjacent brain parenchyma.
Findings:
- The identified tumors present a histological overlap between PMAs and PAs.
- Immunohistochemistry confirmed glial fibrillary acidic protein and oligodendrocyte transcription factor positivity.
- A low Ki-67 proliferation index (approximately 2%) was noted in these cases.
Implications:
- This study documents the existence of pilomyxoid astrocytomas with Rosenthal fibers.
- Clarification of the clinical behavior and prognostic implications of these tumors requires further investigation.
- These findings may necessitate re-evaluation of current classification systems for pediatric low-grade gliomas.
