[Clinicopathological features of polymorphous low-grade neuroepithelial tumor of the young]

Objective: To investigate the clinicopathological features, diagnosis and prognosis of polymorphous low-grade neuroepithelial tumor of the young (PLNTY). Methods: Two cases of PLNTY diagnosed during January 2016 to December 2019 were collected from Ningbo Diagnostic Pathology Center, Zhejiang, China. The clinical features, histopathological characteristics, immunohistochemical and molecular genetic findings were analyzed and the relevant literature was reviewed. Results: The two patients were both female, at the ages of 14 and 25 years, respectively. Both patients presented with seizure attacks. The imaging study showed a mixed signal in the cerebral cortex, located in the occipital and temporal lobes, respectively. Microscopically, the tumors were characterized by the invariable presence of oligodendroglioma-like appearance, often with calcification. Immunohistochemically, the tumors were diffusely and intensely CD34 positive with ramified, CD34-expressing neural elements in regional cortex. The tumors were positive for GFAP, Olig2 and ATRX, and negative for IDH1, Neu N, nestin and EMA. The Ki-67 labeling index was less than 2%. The case number 2 harbored the BRAF V600E mutation, while the case number 1 was negative for both the BRAF V600E mutation and 1p/19q codeletion. Both patients recovered very well and were free of seizures after the following-up of 2 and 24 months, respectively. Conclusions: PLNTY is an uncommon neuroepithelial tumor. Histopathologic and immunohistochemical examinations are necessary for establishing the diagnosis and for excluding oligodendroglioma. PLNTY should be considered as a benign tumor corresponding to WHO Grade I. The prognosis is overall good after complete tumor-resection.