Polymorphous Low-Grade Neuroepithelial tumor of the Young (PLNTY): Two Cases of the Recently Described Epileptogenic Neoplasm With Oligodendroglioma-Like Components and Heavy Calcification

• Published in: American journal of clinical pathology 2018-09, Vol.150 (suppl_1), p.S16-S17
• Main Authors: Zhang, Kuixing, Sassoon, Aaron
• Format: Article
• Language: English
• Subjects: Brain cancer; Calcification; CD34 antigen; Fibroblast growth factor receptor 2; Fibroblast growth factor receptors; Glial fibrillary acidic protein; Immunohistochemistry; Karyotypes; Leukocytes (eosinophilic); Microvasculature; Mitosis; Mutants; Oligodendroglioma; p53 Protein; Temporal lobe; Tumor cells; Tumors; Young adults
• ISSN: 0002-9173; 1943-7722
• DOI: 10.1093/ajcp/aqy090.040

Abstract Epileptogenic tumors affecting children and young adults are a diverse collection of neuroepithelial neoplasms. Polymorphous low-grade neuroepithelial tumor of the young (PLNTY) is a recently described entity with a distinct morphologic, immunohistochemical, and molecular profile, and it is not part of the present 2016 WHO classification of CNS tumors. Here we report two cases diagnosed with PLNTY; both are 12-year-old females with seizure attacks. One patient has a left lateral temporal lobe lesion, heavily calcified, showing solid and cystic areas, measuring 2.6 × 2.6 × 1.8 cm. The other has a left parasagittal parietal lesion with heavy calcification, measuring 2.8 × 1.5 × 2.2 cm. Both patients underwent resection to relieve the symptoms. Microscopically, the tumors from both cases exhibit an oligodendroglial-like appearance and intratumoral heterogeneity. Heavy calcifications are identified. Mitosis is absent and there is no microvascular proliferation or necrosis, consistent with WHO grade I. Notably, there are no Rosenthal fibers, eosinophilic granular bodies, or neurocytic rosettes. Immunohistochemically, the tumor cells from both cases are positive for GFAP and CD34 and negative for mutant IDH1 (IDH1-R132H), BRAF V600E, and p53 protein. ATRX expression is retained and codeletion of 1p/19q is not detected in both cases. Complex molecular karyotype is observed, and loss of 10q23.31q26.13 (adjacent to and potentially disrupting FGFR2) is detected in one case. The diagnosis of PLNTY is established based on morphology and immunohistochemistry. In summary, PLNTY is an epileptogenic tumor characterized by an oligodendroglial-like appearance, heavy calcification, and CD34 expression as seen in these two cases. Many of these tumors have BRAF V600E mutation, and others have unusual FGFR2 or FGFR3 receptor abnormalities. PLNTY may represent a distinct biological entity for pediatric epileptogenic low-grade neuroepithelial tumor.