Contributed by Chris Englund1, Daniel Silbergeld1,2, Ellsworth C. Alvord, Jr.1, Randy Small1, and Robert F. Hevner1
Departments of 1Pathology and 2Neurological Surgery, University of Washington, Seattle, Washington
A 24-year-old woman presented with a one-year history of bifrontal headaches that had recently worsened. After admission to the hospital, the patient displayed no other symptoms and no acute worsening of the headaches.
A CT scan was performed and demonstrated a well-circumscribed, calcified lesion, approximately 2 cm in diameter, located in the right frontal lobe beneath the coronal suture (Fig. 1). The lesion was isointense on T2-weighted MRI, and showed minimal enhancement on post-contrast sagittal T1-weighted images (Fig. 2).
GROSS AND MICROSCOPIC PATHOLOGY:
The patient underwent a right frontal craniotomy with Stealth guidance. The bisected specimen showed a fleshy red/tan tumor, surrounded by a thin rim of normal white matter (Fig. 3). The border between tumor and white matter was remarkably distinct on both gross and microscopic inspection (Fig. 4).
Hematoxylin and eosin stained sections showed predominantly small round tumor cells, many with perinuclear halos, clustered in groups and surrounded by hypocellular areas, or by microcysts filled with bluish gray material (Fig. 5). Focally, the tumor contained ganglioid cells with larger nuclei, prominent nucleoli, and abundant, basophilic cytoplasm (Fig. 6). Synaptophysin immunoreactivity strongly labeled the hypocellular areas (Fig. 7). The MIB-1 labeling index was less than 1% (not shown). The mature neuronal marker NeuN was variably expressed: in some areas NeuN was expressed by the majority of tumor cells, but in other areas by very few tumor cells (Fig. 8). Ganglioid cells in this tumor were uniformly NeuN+.
To determine if NeuN+ tumor cells were mitotically active or inactive, we performed double immunofluorescence using antibodies against NeuN and Ki-67 (MIB-1 antigen). There was no co-localization of NeuN and Ki-67 in areas of either high (Fig. 9) or low (Fig. 10) NeuN labeling.