Aggressive papillary glioneuronal tumor: case report and literature review.

Papillary glioneuronal tumors (PGNT) are a rare, recently described form of mixed neoplasm composed of glial and neuronal components. PGNT usually occur in children and young adults, and typically demonstrate low-grade pathology, with a low proliferative index of 1-3%. Here we describe a newly diagnosed case of PGNT with a more aggressive phenotype that required irradiation and chemotherapy. The patient was a 19-year-old female who developed progressive headaches and visual seizures. An MRI revealed a heterogeneously enhancing solid mass in the left temporo-occipital region, with significant surrounding edema and mass effect. The mass was resected under stealth guidance without complication. Postoperative MRI scans showed patchy enhancement and residual T2 and FLAIR abnormality. Pathology revealed a highly cellular neoplasm with papillary-like structures, containing cells with glial and neuronal differentiation. Regions of mitoses and focal necrosis were noted, along with a Ki-67 labeling index of 26%. The diagnosis was aggressive PGNT, and treatment consisted of conformal irradiation and concomitant temozolomide over 6 weeks. Postirradiation follow-up MRI scans demonstrated a reduction of residual enhancement and FLAIR abnormality. The patient continues standard-dose adjuvant temozolomide on a monthly basis, with further improvement on subsequent MRI scans and a stable neurologic exam. This patient demonstrates that PGNT may, in rare cases, display an aggressive clinicopathologic phenotype that requires a therapeutic approach more consistent with a high-grade glioma.