The clinicopathological characteristics of non-specific variant of dysembryoplastic neuroepithelial tumor

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.

DOI: 10.3969/j.issn.1672-6731.2016.12.008