A peculiar histopathological form of dysembryoplastic neuroepithelial tumor with separated pilocytic astrocytoma and rosette‐forming glioneuronal tumor components

Abstract

Dysembryoplastic neuroepithelial tumors (DNTs) mostly display typical clinical, neuroimaging and histopathological features, but sometimes they reveal heterogeneous or non-specific morphology, which results in diagnostic dilemmas. We present a case of a young adult with longstanding, intractable epilepsy associated with a multinodular cystic lesion in the temporal lobe. The lesion consisted of morphologically different components. In particular, a few cortical nodules displayed a specific glioneuronal element with floating neurons typically found in DNT. Two large, well-circumscribed nodules were entirely composed of biphasic, piloid, astroglial patterns that corresponded strictly to a pilocytic astrocytoma. The well-defined areas, which contained numerous distinct neurocytic-like rosettes, were identical with rosette-forming glioneuronal tumors (RGNTs). This type of neurocytic rosette was widespread within the surrounding piloid background. Some solid nodules exhibited increased cellularity, oligodendroglioma-like elements and a focal ribbon cell arrangement. The lesion was associated with advanced reactive gliosis and foci of dysplastic changes in the adjacent cortex. The clinico-radiological and main histopathological features were consistent with a diagnosis of a complex variant of DNT composed of pilocytic and rosette-forming glioneuronal components. Although both piloid tissue and rosette-like formations have been occasionally mentioned in DNT lesions, the present case of DNT was unique in its well-circumscribed, separate pilocytic and RGNT nodules. We concluded that it represented an unusual, mixed pilocytic/RGNT variant of DNT.

An epilepsy‐associated glioneuronal tumor with mixed morphology harboring FGFR1 mutation

“…Collins et al claimed that the presence of a distinct neurocytic rosette, even small amount, might support the diagnosis of RGNT . Conversely, rosette‐like structure has also been detected in DNTs . Although the present case had a small amount of neurocytic rosette, delicate fibrillary neuropil processes inside the ring‐array OLCs was unclear.…”

“…4 Conversely, rosette-like structure has also been detected in DNTs. [15][16][17] Although the present case had a small amount of neurocytic rosette, delicate fibrillary neuropil processes inside the ring-array OLCs was unclear. In addition, the cortex of the temporal lobe is not a common location of RGNT.…”

“…Several overlapping features exist between RGNT and DNT . Intriguingly, the first RGNT case was reported as a DNT of the cerebellum .…”

“…Several overlapping features exist between RGNT and DNT. 5,[14][15][16][17] Intriguingly, the first RGNT case was reported as a DNT of the cerebellum. 18 Collins et al claimed that the presence of a distinct neurocytic rosette, even small amount, might support the diagnosis of RGNT.…”

Dysembryoplastic neuroepithelial tumour: insight into the pathology and pathogenesis

“…In addition, rare mixed tumours composed of a DNT lesion with components of rosette forming glioneuronal tumour [38], pilocytic astrocytoma [44] or pleomorphic xanthoastrocytoma [30] have been described.…”