Intraocular astrocytoma and its differential diagnosis.

Astrocytomas arising within the eye display 2 distinct histologies: one comprises interlacing bundles of spindle-shaped cells mixed with a minority of polygonal cells, and the other consists of large cells with abundant glassy cytoplasm (gemistocytic astrocytes) indistinguishable from cells found in subependymal giant cell astrocytoma. Both histologic patterns express glial fibrillary acid protein diffusely, are biologically benign, and are frequently associated with dysgenic syndromes, particularly tuberous sclerosis complex. Tumors with gemistocytes, however, demonstrate a greater propensity for invasive growth. The clinical history may provide information to guide the pathologist in distinguishing intraocular astrocytoma from reactive astrocytosis, conditions that are histologically similar. It remains to be determined if other types of primary intraocular glioma exist or whether some degree of ependymal or oligodendroglial differentiation can accompany reactive astrocytosis.