Abstract:

Background Dysembryoplastic neuroepithelial tumor (DNT) is a benign neuronal and mixed neuronal-glial tumor (WHOⅠ) and may present 3 histological subtypes: simple, complex and non-specfic. Non-specific DNT is very difficult to be diagnosed because of the lack of "specific glioneuronal element". Herein we describe one case of non-specific DNT in frontal lobe. The radiological and clinicopathological features of this lesion, as well as its diagnosis and differential diagnosis are discussed. Methods  The clinical data of one patient with non-specific DNT was presented retrospectively. Gross totally resected mass was routinely paraffin embedded and stained with hematoxylin and eosin. Immunohistochemical staining was used to detect antigen expression. 1p/19q co-deletion was also detected by fluorescence in situ hybridization (FISH) utilizing Vysis dual-color probe. Results  A 16-year-old boy presented with recurrent headache and dizziness. He had a history of at least two complex seizures over the previous 3 years. MRI revealed a small, well-demarcated cystic lesion within the cortex of right frontal lobe with hypointense on T₁WI and hyperintense on T₂WI. There was no obvious peritumoral edema or enhancement. The tumor was removed totally. The histological sections revealed cystic area with neuroglial nodule attached on the cyst wall. The nodule was mainly composed of oligodendrocytic-like components and scattered neuronal cells. Typical "specific glioneuronal element" was not seen. "Microcolumnar arrangement" was found in the adjacent cortex of lesion, which conformed with the histological features of focal cortical dysplasia (FCD) typeⅠ a. Immunohistochemically, the oligodendrocytic-like component was diffusely positive for synaptophysin (Syn) in cytoplasm and oligodendrocytes transcription factor-2 (Olig-2) in nuclei, focally positive for CD34, S-100 protein (S-100) and BRAF V600E in cytoplasm. However, there was no positive signal found for detection of glial fibrillary acidic protein (GFAP) and isocitrate dehydrogenase 1 (IDH1) R132H. Ki-67 labeling index was 2%. FISH showed that there was no 1p/19q co-deletion. Based on clinical presentation and histological findings, a final diagnosis of non-specific variant of DNT, WHO Ⅰ, accompanied by FCD Ⅲ b, was made. Accessory treatment was not given postsurgically. The patient was regularly followed-up for one year. Head MRI was reexamined 3 and 6 months after operation. No recurrence or seizure occurred. Conclusions  In clinical practice, non-specific variant of DNT is diagnostic challenging and may be confused with other low-grade gliomas even if there are typical clinical manifestations and radiological appearance of DNT exhibited in lesion. The accurate diagnosis of this tumor is obtained from carefully histological inspection and a panel of immunohistochemical and molecular study for CD34, IDH1 R132H, BRAF V600E and 1p/19q co-deletion.

Key words: Neoplasms, neuroepithelial,  Frontal lobe,  Magnetic resonance imaging, Pathology,  Immunohistochemistry

摘要：

研究背景 胚胎发育不良性神经上皮肿瘤是神经元和混合性神经元-胶质肿瘤分类中的WHOⅠ级肿瘤，分为单纯型、复合型和非特殊型3 种组织学亚型。由于缺乏典型的“特异性胶质神经元成分”，非特殊型胚胎发育不良性神经上皮肿瘤成为临床极具挑战性的诊断难点。本文回顾分析1 例非特殊型胚胎发育不良性神经上皮肿瘤患儿的临床资料，探讨该少见亚型的诊断与鉴别诊断要点。 方法与结果 男性患儿，16 岁，因反复头痛、头晕，影像学检查发现右侧额叶皮质病变入院。过去3 年内至少癫痫发作2 次，抗癫痫药物治疗效果不佳。MRI 显示病灶呈长T₁、长T₂ 信号，无瘤周水肿，增强扫描未见强化。手术全切除病变，肿瘤内可见囊性区和囊壁上附着的神经胶质增生结节。神经胶质结节主要由少突胶质细胞瘤样细胞弥漫性分布构成，可见一些散在分布的神经元，未见典型“特异性胶质神经元成分”，邻近大脑皮质部分区域可见“微柱结构”形成，符合局灶性皮质发育不良（FCD）Ⅰa 型。免疫组织化学染色，少突胶质细胞瘤样细胞胞质突触素和胞核少突胶质细胞转录因子2 弥漫性强阳性，胞质CD34、S-100 蛋白和原癌基因BRAF V600E 灶性阳性，Ki-67 抗原标记指数约2%。荧光原位杂交未见1p/19q-共缺失。最终病理诊断为（右侧额叶）胚胎发育不良性神经上皮肿瘤，非特殊型，WHOⅠ级，伴局灶性皮质发育不良Ⅲb 型。术后未行放射治疗和药物化疗，规律随访1 年，术后第3 和6 个月时分别复查头部MRI，未见肿瘤复发，也未再出现癫痫发作。 结论 非特殊型胚胎发育不良性神经上皮肿瘤组织学亚型临床少见，易误诊为低级别胶质瘤，青年患者出现癫痫发作和大脑皮质病变时，胚胎发育不良性神经上皮肿瘤须作为第一怀疑诊断而加以鉴别，结合CD34、R132H-突变的异柠檬酸脱氢酶1、BRAF V600E 等免疫组织化学检测和1p/19q分子检测对明确诊断和组织学分型十分重要。

关键词: 肿瘤, 神经上皮, 额叶, 磁共振成像, 病理学, 免疫组织化学