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

Objective: To investigate the clinicopathological features and differential diagnosis of polymorphous low-grade neuroepithelial tumor of the young (PLNTY). Methods: Five cases of PLNTY diagnosed at the First Affiliated Hospital and Affiliated Brain Hospital of Nanjing Medical University, Nanjing, China from 2019 to 2021 were collected. All cases were evaluated using clinical and imaging data, histology, immunohistochemical staining and molecular genetics. The relevant literature was reviewed. Results: There were two male and three female patients, aged 10 to 39 years, with an average age of 25 years. Clinically, the tumors were in the temporal lobe (3 cases), the lateral ventricle (1 case) and the left head of caudate nucleus (1 case). The clinical manifestations included epilepsy in 3 cases, right visual disturbance in 1 case, and post-trauma incidental finding in 1 case. Microscopically, the lesions were characterized with infiltrative growth, cellular pleomorphism (oligodendroglioma-like cells were always present, with low-grade, pleomorphic nuclei) and variable calcifications. Immunohistochemically, the tumor cells were positive for GFAP and Olig2. They also showed intense and diffuse expression of CD34 while CD34 expressing ramified neural elements were present in regional cortex. Ki-67 proliferation index was less than 3%. Molecular genetics showed the BRAF V600E mutation in 2 cases, the PAK5-Q337R missense mutation in 1 case, the FGFR2-CTNNA3 fusion in 1 case, and the FGFR2-INA and FGFR2-PPRC1 concomitant fusion in 1 case. No postoperative chemoradiotherapy was given. Follow-up intervals ranged from 3 to 29 months while no recurrence or metastasis was identified. Conclusions: PLNTY is uncommon. A definite diagnosis of PLNTY relies on histopathological examination and molecular genetics. It is important to distinguish PLNTY from high grade gliomas and avoid overtreatment. The recently reported the PAK5-Q337R missense mutation and the FGFR2-PPRC1 gene fusion in PLNTY may help diagnose and understand the pathogenesis of PLNTY.目的： 探讨青少年多形性低级别神经上皮肿瘤（polymorphous low-grade neuroepithelial tumor of the young，PLNTY）的临床病理特征、诊断及鉴别诊断要点。 方法： 收集2019—2021年南京医科大学第一附属医院和南京医科大学附属脑科医院手术诊治经病理确诊的PLNTY 5例，对其临床及影像学特点、组织学形态、免疫表型及分子遗传学改变进行分析总结，并复习文献。 结果： 患者男性2例，女性3例；年龄10~39岁，平均年龄25岁；肿瘤位于颞叶3例，侧脑室、左尾状核各1例；临床表现癫痫3例、右眼视力下降1例，1例因外伤后体检发现。镜下观察：肿瘤特征性表现为浸润性生长、瘤细胞多形性（均可见少突胶质细胞瘤样细胞、细胞核呈低级别、多形性）及不同程度钙化。免疫组织化学：肿瘤细胞胶质纤维酸性蛋白、少突胶质细胞转录因子阳性，CD34弥漫强阳性，周围脑组织可见散在CD34阳性细胞，Ki-67阳性指数均小于3%。分子遗传学：BRAF V600E突变2例，PAK5-Q337R基因错义突变1例，FGFR2-CTNNA3基因融合1例，1例伴有FGFR2-INA和FGFR2-PPRC1基因融合。术后均未行放化疗，随访3~29个月，未见复发转移。 结论： PLNTY罕见，确诊依赖于病理形态及分子遗传学，认识该肿瘤的重要性在于与高级别胶质瘤鉴别，避免过度治疗，本研究新报道PAK5-Q337R错义突变和FGFR2-PPRC1基因融合，拓宽了PLNTY的分子遗传学谱系。.