Papillary glioneuronal tumors: a review of clinicopathologic and molecular genetic studies

This study was designed to evaluate 4 new cases of papillary glioneuronal tumors (PGNTs), 2 of which had atypical histologic features, provides extensive IHC characterization, performed comparative genomic hybridization in 2 of our cases, and reviews the recent literature. The study group comprised 3 women and 1 man, with ages ranging from 12 to 75 years. Patients presented with seizures (n = 3) or muscle spasm (n = 1), and the tumors were located in the supratentorial region of the brain (3 in the frontal and 1 in the parietotemporal lobe). The 2 atypical tumors showed a moderately high mitotic rate (4 and 7/10 HPF, each), vascular endothelial hyperplasia, and necrosis. Tumor cells expressed both neuronal and glial markers, but the degree of neuronal versus glial expression was varied. None of the tumors expressed p53, EGFR wild type/vIII, IDH1, or CD34; however, nestin, galectin-3, and S100 were positive in the tumor cells. No EGFR gene amplification or 1p/19q deletion was found by fluorescence in situ hybridization. Half of the cases revealed PTEN loss by immunohistochemistry, and MGMT methylation was positive in 3 cases by MGMT methylation-specific polymerase chain reaction. Ultrastructurally, either astrocytic or neuronal differentiation was observed, but we could not identify any hybrid cells. An array-based comparative genomic hybridization study revealed loss of 1q, 6p, 8p, 9p, 9q, and 16q and gain of 2q, 3p, 5q, 6p, 7q, 10q, 16q, 19p, and 22q in 2 cases simultaneously. The first patient, who underwent subtotal resection, died because of progression of the tumor within 9 months after surgery; however, 2 patients were symptom free and progression free at 34 and 48 months after gross total resection (the patient 2: plus radiotherapy, the patient 3: no adjuvant chemo- or radiotherapy). The last patient developed seizures after a long symptom-free period (40 mo) with no evidence of tumor recurrence. Our 4 new cases, in conjunction with the literature review, reinforce that PGNTs are tumors that usually occur in young adults (mean age, 24 y); they are most often cystic with a mural nodule or are cystic/solid, supratentorial, closely located with the ventricle, molecularly genetically different from astrocytic or oligodendroglial tumors, and indolent in behavior. Cases (2 of 4 in our study) with atypical histologic features or that occur in advanced age (75 y), and sporadic reports of histologically or biologically aggressive PGNTs, serve to remind pathologists that the full spectrum of PGNTs is as yet unknown.