GANGLIOGLIOMA - AN ULTRASTRUCTURAL AND IMMUNOHISTOCHEMICAL STUDY

BACKGROUND. Ganglioglioma is a rare, mixed neuronal-glial neoplasm of the central nervous system that occurs in young patients and has a ben ign clinical course. METHODS. To define the immunophenotypic and morph ologic features of ganglioglioma precisely, 27 specimens were studied by routine histochemistry, 21 specimens by immunochemistry, and 14 spe cimens were examined at the ultrastructural level. RESULTS. The age of the 27 patients, 14 males and 13 females, ranged from 3 to 52 years ( mean, 22 years). The most commonly affected site was the temporal lobe (13 patients). Three patients experienced a local recurrence. Microsc opically, the tumors were comprised of well differentiated, somewhat a bnormal neurons as well as glial cells, the latter including astrocyte s of fibrillary (59%) and pilocytic (41%) type. Scant mitotic activity was observed in 2 tumors (7%). Glial cells of all rumors were immunor eactive for glial fibrillary acidic protein, S-100 protein, and viment in. Ki-67 labeling indices (LI) ranged from 0.6 to 10.5% (mean, 2.7%) and p53 LI from 1.1 to 42.4% (mean, 15.6%). Ki-67 and p53 LI in recurr ent tumors were significantly higher than those of nonrecurrent ones ( P = 0.036 and 0.026, respectively). No examples of anaplastic transfor mation were encountered. Immunohistochemically, many neuronal cells we re positive for synaptophysin (100%), Class 3 beta-tubulin (100%), neu rofilament protein (90%), and chromogranin A (86%), in addition to S-1 00 protein (71%) and, occasionally, vimentin (24%). Ultrastructural ch aracteristics of neuronal cells included the presence of numerous, 100 -230-nanometer dense core granules within both perikarya and cell proc esses, well developed rough endoplasmic reticulum, microtubules within cell processes, and synapses associated with clear vesicles. Astrocyt ic cells usually contained abundant intermediate filaments; their cell membranes, when abutting the stroma, were covered by basal lamina. CO NCLUSIONS. Gangliogliomas are comprised of well differentiated neurona l cells and glial cells that are very often of pilocytic type. No cell s with features intermediate between neurons and glia were observed. N euronal cells are characterized by prominent neurosecretory features d istinct from those of normal neurons in the central nervous system. Hi gher Ki-67 and p53 LI may indicate more aggressive behavior.