Optic pathway gliomas generally fall under the World Health Organization’s classification of a grade I pilocytic astrocytoma, usually Juvenile Pilocytic Astrocytomas (JPA).
Tumors are composed of:
- Immature astrocytes, the nuclei of which are regular without mitoses
- Rosenthal fibers are common
- Microcystic degeneration seen
- Focal calcification sometimes present
Several histological patterns of these tumors have been described:
- Astrocytic and oligodendroglial proliferation
- Reticular pattern, involves microcystic foci with mucous-like fluid
- Leptomeningeal invasion, involves fibrillated cells in bundles
Occasionally pathology is positive for grade II fibrillary astrocytoma.
These tumors are slow growing and are not generally associated with metastatic deposits.
High grade lesions are very rare in children.
The suggested precursor cell is the 02A cell, a glial precursor present in the optic pathway. This precursor can differentiate into both astrocytes and oligodendrolia, which could account for the presence of these cells within the tumor.
Because of the location of these tumors, biopsies are not always performed.
Tumors tend to be more aggressive in adult patients. Tumor de-differentiation is rarely seen in younger children with optic pathway tumors, but may be observed in older children and adults. The tumor may become an anaplastic astocytoma or glioblastoma multiforme.