[Pilomyxoid astrocytoma: a clinicopathologic study of three cases]
Lian Chen1, Yin Wang, Xiong-zeng Zhu
1Department of Pathology, Children's Hospital, Medical School, Fudan University, Shanghai 200032, China.
Objective:
To study the clinicopathologic features of pilomyxoid astrocytoma (PmA).
Methods:
The clinical and pathologic features in 3 cases of PmA were analyzed. Immunohistochemical study for glial fibrillary acidic protein (GFAP), CD34 and Ki-67 was performed on paraffin-embedded sections by standard EnVision method.
Results:
All the 3 cases occurred in female patients at the age of 10 months, 10 years and 19 years respectively. Two cases were located in the third ventricle, while the remaining case was located at the optic pathway. Histologically, the tumor was composed of bipolar spindle cells setting in a strikingly mucinous background. There was a marked proliferation of vessels within the tumor. In some areas, the tumor cells exhibited an angiocentric growth pattern. The biphasic pattern noted in a classic pilocytic astrocytoma was not found in PmA. Rosenthal fibers and eosinophilic granular bodies were also not identified. Immunohistochemcal study showed that the tumor cells were diffusely positive for GFAP. The Ki-67 labeling index measured less than 1%. CD34 highlighted mainly the vascular networks.
Conclusions:
PmA is a distinctive variant of pilocytic astrocytoma with subtle histologic differences. Compared with conventional pilocytic astrocytoma, PmA behaves more aggressively. Some cases tend to occur in older children and adolescents. Immunohistochemical study for GFAP is helpful in differential diagnosis.
Insights
Pilomyxoid astrocytoma (PmA) is a distinct pilocytic astrocytoma variant. PmA exhibits subtle histologic differences and a more aggressive clinical behavior than conventional pilocytic astrocytoma.
Area of Science:
- Neuro-oncology
- Pediatric Pathology
- Molecular Pathology
Context:
- Pilomyxoid astrocytoma (PmA) is a rare variant of pilocytic astrocytoma.
- Understanding its clinicopathologic features is crucial for accurate diagnosis and management.
Purpose:
- To investigate the clinicopathologic characteristics of pilomyxoid astrocytoma.
- To differentiate PmA from conventional pilocytic astrocytoma using histological and immunohistochemical markers.
Summary:
- Analyzed 3 cases of PmA, noting female predominance and occurrence in children and adolescents.
- Histological findings revealed bipolar spindle cells in a mucinous background with prominent vasculature, distinct from classic pilocytic astrocytoma.
- Immunohistochemistry showed diffuse GFAP positivity in tumor cells, low Ki-67 index (<1%), and CD34 highlighting vascular networks.
Impact:
- PmA represents a distinct entity with subtle histological differences and a more aggressive behavior compared to conventional pilocytic astrocytoma.
- Findings aid in the differential diagnosis of pediatric brain tumors.
- Highlights the utility of GFAP immunohistochemistry in distinguishing PmA.
