The patient had already had a laminectomy and small biopsy.
Sections show a neuropil in which there are increased numbers of neurons. Some of these neurons are oriented in various directions. Many of the neurons have a rounded appearance and some of the neurons have an eccentric-placed nucleus. The cellularity of the non-neuronal background is minimally increased and occasional clusters of glial cells are seen. The Bielschowski stain shows filamentous staining of the cell bodies of neurons which are large and have irregular shapes. There are occcasional structures reminescent of Rosenthal fibres. In some regions there are increased numbers of blood vessels.
Immunohistochemistry shows that the neuronal cell bodies are positive for synaptophysin and have a dense population of terminal boutons on their surface. Many of the neurons which are irregular in shape are positive for phosphorylated neurofilament. There is punctate granular positivity for chromogranin in many of the neurons. The glial fibrillary acidic protein stain shows staining of astrocytes and their processes in the background of the neuronal cell population. Immunohistochemisty for MIB-1 shows only occasional positive nuclei.
FINAL DIAGNOSIS: The lesion is unusual. It is only modestly hypercellular and the hypercellularity is due mainly to the presence of neurons which are somewhat atypical. These neurons stain for phosphorylated neurofilament and synaptophysin and have large numbers of terminal boutons on their surface. There are glia present which are few in number but occasional form small clusters. This case was shown to [...], an international authority on CNS tumors and it was felt that this is a ganglioglioma.
feature images from this case