Dysembryoplastic neuroepithelial tumor differential diagnosis
The differential diagnosis of DNET includes oligodendrogliomas, low-grade gliomas, gangliogliomas and pleomorphic xanthoastrocytomas (PXA). Clinical features, imaging findings, and histologic findings are key in making the diagnosis
Low-grade epilepsy-associated neuroepithelial tumors (LEATs) create a diagnostic challenge in daily practice and intraoperative pathological consultation (IC) in particular.
Specific DNT is a homogeneous group of tumours sharing characteristics of pediatric low-grade gliomas: a quiet genome with a recurrent genomic alteration in the RAS–MAPKsignalling pathway, a distinct DNA methylation profile, a good prognosis but showing progression in some cases. The “non-specific/diffuse DNTs” subgroup encompasses various recently described histo-molecular entities, such as PLNTY and Diffuse astrocytoma MYB or MYBL1 altered 1).
Intraoperative squash smear cytology are extremely useful for accurate diagnosis; however, the knowledge of cytopathologic features of LEATs is based on individual case reports. Kurtulan et al. discuss the 3 most common and well-established entities of LEATs: ganglioglioma (GG), dysembryoplastic neuroepithelial tumor (DNT), and papillary glioneuronal tumor (PGNT).
Thirty patients who underwent surgery for GG, DNT, and PGNT between 2001 and 2021 were collected. Squash smears prepared during intraoperative consultation were reviewed by 1 cytopathologist and an experienced neuropathologist.
Among the 30 tumors, 16 (53.3%) were GG, 11 (36.6%) DNT, and 3 (10%) PGNT. Cytomorphologically, all of the 3 tumor types share 2 common features such as dual cell population and vasculocentric pattern. GG smears were characteristically composed of dysplastic ganglion cells and piloid-like astrocytes on a complex architectural background of thin- to thick-walled vessels. DNT, on the other hand, showed oligodendroglial-like cells in a myxoid thin fibrillary background associated with a delicate capillary network. Common cytological features of PGNT were hyperchromatic cells with narrow cytoplasm surrounding hyalinized vessels forming a pseudopapillary pattern and bland cells with neuroendocrine nuclei dispersed in a neuropil background.
A higher diagnostic accuracy can be obtained when squash smears are applied with frozen sections. However, it is important to integrate clinical and radiologic features of the patient as well as to know the cytopathologic features of the LEAT spectrum in the context of differential diagnosis to prevent misinterpretation in the IC 2).
A 29-year-old male from Bolivia, who lived in Spain, presented seizures and a multicystic brain lesion, initially suspected to be a dysembryoplastic neuroepithelial tumor (DNET). He underwent gross total resection of the mixed solid/cystic lesion. Pathology revealed gliosis, multiple interconnected cystic cavities with fibrous walls, inflammatory cell infiltration and no necrotizing granulomatous reaction. Inside the cavities, a parasitic form was identified as the larva of the cestode Spirometra mansoni. At 1-year follow-up, the patient had no deficits and was seizure free. Clinicians should be alerted to the possible existence of this rare entity in Europe, especially in patients from endemic areas with a possible infection history as well as “wandering lesions” on the MRI 3).
She was transferred from other Hospital after finding a right temporal lesion on MRI in the context of seizures.
Unprovoked focal seizure. Paroxysmal episodes of blank stare, unresponsiveness, Orofacial Dyskinesia, Guttural sounds, and hypersalivation lasting approximately 30 seconds. Transient global amnesia. He refers to a similar episode a month ago.
Cranial magnetic resonance imaging without and with intravenous contrast (8ml gadovist) was performed with the usual protocol: sagittal T1 TSE, axial T2 TSE, coronal T2 TSE, axial T2 FLAIR, axial T2 EG and axial diffusion.
A signal alteration centered on the anterior pole of the right temporal lobe of approx. 2.2×2.7×1.7cm (TxAPxCC) associates diffuse cortical thickening and the presence of a heterogeneous lesion with a solid and microcystic component that is hypointense in the T1 sequences and hyperintense in the T2 sequences, it also presents a hyperintensity of the peritumoral signal and an increase in diffusion in DWI sequences without presenting signal drop in the ADC. The perfusion sequences did not show an increase in cerebral perfusion at this level with ADC: 1.3. This lesion presents a heterogeneous contrast uptake, drawing attention to the presence of a solid pole adjacent to the dura that presents intense enhancement, but does not present dural enhancement. These findings may be related to a dysembryogenic neuroepithelial tumor (DNET) or to a Ganglioglioma as the main differential diagnoses. No microbleeds were seen in the gradient echo T2 sequence or calcifications. The rest of the cerebral, cerebellar and brainstem parenchyma show no morphological or signal alterations. Middle line centered. Free basal and perimesencephalic cisterns. Centered ventricular system with preserved ventricular size. The main arterial and intracranial venous vessels show a caliber and signal void within normality. Unoccupied paranasal sinuses and mastoid cells. Slight descent of the cerebellar tonsils not significant (2 mm).
Heterogeneous lesion centered on the anterior temporal pole of the right temporal lobe with a solid / cystic component and enhancement after contrast administration, with tumor characteristics suggesting a Dysembryoplastic neuroepithelial tumor (DNET) or a ganglioglioma as the main differential diagnoses.