胚胎发育不良性神经上皮肿瘤（DNET）

History: A 33-year-old woman presents with complex partial seizures.

Your diagnosis？

Diagnosis: Dysembryoplastic neuroepithelial tumor (DNET)                      胚胎发育不良性神经上皮肿瘤（DNET）

Pathophysiology/epidemiology

Dysembryoplastic neuroepithelial tumors are benign, slow-growing, glioneuronal World Health Organization (WHO) grade 1 tumors arising from cortical or deep gray matter. They are solid tumors with cystic/microcystic components that usually occur in younger patients, with the peak age of presentation between ages 10 and 30 years. They are more common in males than females. They are a common cause of tumor-related intractable epilepsy. They are most commonly associated with complex partial seizures in the temporal lobe.

The histopathologic hallmark of DNETs is the presence of the specific glioneuronal element (SGNE), which consists of small, round, oligodendroglial-like cells arranged in columns around a central core of axon bundles that run perpendicular to the cortical surface. DNETs are associated with adjacent cortical dysplasia in up to 80% of cases. There are three main histologic forms. The simple form only contains SGNE. The complex form contains SGNE and glial nodules, multinodular architecture, and focal cortical dysplasia. The nonspecific form has similar neuroimaging features but no SGNE. There have been only a few reported cases of malignant transformation, which have been associated with extratemporal locations (Moazzam et al, 2014).

Imaging features

Most commonly located in the temporal lobe (lateral, medial and amygdala/hippocampus complex). Can also be found in the frontal lobe, caudate, and cerebellum.

Pseudocysts with “bubbly appearance” are characteristic. The fluid collections lack epithelial or membranous linings. They are hypointense on T1, hyperintense on T2, and mixed signal on FLAIR. They vary in size from 1 mm to 5 cm.

Surrounding noncystic tissue usually has hypo- or isointense signal on T1 and hyperintense signal on T2 and FLAIR.

There is contrast enhancement in 20% to 30% of cases, which is usually nodular or ring-like in the periphery of the cysts.

There is no restricted diffusion on diffusion-weighted imaging (DWI).

Calcification has been seen in approximately 10% of cases.

Clinical presentation and treatment

Children and young adults with DNETs typically present with longstanding, treatment-resistant partial seizures. Patients can also present with progressive neurological deficits, such as sensory deficits, behavioral disorders, or intellectual disability. DNETs arising in the cerebellum can present with ataxia. These lesions are very slow-growing but require surgical resection to treat epilepsy. They have been shown to account for approximately 15% of surgical epilepsy tumors. Surgery is associated with a very good prognosis and low recurrence.

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