Dysembryoplastic neuroepithelial tumor (DNET)

Case Discussion

The patient went on to have a resection. 

Histology

Microscopic Description: 

Sections show the specimen to contain a low-grade tumor that appears to be relatively circumscribed. The tumor is characterized by varied appearances that range from a more solid fibrillar appearance with numerous Rosenthal fibers, to a less compact pattern with cells that contain clear perinuclear cytoplasm, within a loosely microcystic background. Individual tumor cells display round to elongated nuclei. Nuclear pleomorphism is mild to moderate. Mitotic activity is not increased. Vascular neogenesis and areas of necrosis are not seen. In areas, the tumor is located within superficial cortex, and renders an exophytic appearance. Although some “floating” neurons may be present, they could well represent entrapped neurons. A well defined “specific glioneuronal element” that is diagnostic of DNET is not seen. Neuronal satellitosis is evident, and linear profiles of cells are also observed in the vicinity of the tumor. The appearance is consistent either with reactive oligodendrogliosis, or peripheral extension of the tumor. As previously mentioned, this low-grade tumor is interpreted as being a 'circumscribed' glioma rather than a diffusely infiltrating glioma.

Final Diagnosis: Dysembryoplastic neuroepithelial tumor (DNET), non-specific variant

Comment: The “specific glioneuronal element” of DNET was not well defined in this low-grade neoplasm. An element resembling pilocytic astrocytoma is very prominent. The “non-specific variant” of DNET is a somewhat controversial designation that may encompass a variety of histologically diverse lesions that are characterized by the following common features: young age, superficial location, and an indolent course that require no further treatment beyond initial surgery. This tumor falls into this category.