[Glioneuronal tumor with neuropil-like island: report of four cases and review of literature].

To investigate the clinicopathologic features of glioneuronal tumor with neuropil-like island (GTNI).Four cases of intracranial and spinal GTNI, including three cases of WHO grade Ⅲ, and one case of WHO grade Ⅱ with grade Ⅲ recurrence. HE and immunohistochemical (IHC) staining were used for pathologic analysis. Fluorescence in situ hybridization (FISH) was used to detect tumor genetic changes. Related literatures were reviewed.Microscopically, neuropil-like islands of varying sizes were seen within a background of glial proliferation, which showed features of astrocytoma or oligoastrocytoma. Neuropil-like islands were focal or circumscribed oval islands of varying sizes. Focally ganglion-like cells were seen. IHC staining revealed that in neuropil-like island area, the neuronal nuclei (Neu-N) as well as the cells around the neuropil-like island expressed oligodendrocyte lineage transcription factor-2 (Olig-2), and synaptophysin. The background glioma cells expressed S-100, glial fibrillary acidic protein (GFAP), vimentin and Olig-2, and the number of p53 positive cells was 10%-50%.In the neuropil-like island area, the Ki-67 labeling index was less than 3%, while in the astrocytoma area it was around 10%-25%.By FISH testing, four cases were no deletion of 1p/19q and PTEN, also no amplification of epidermal growth factor receptor.GTNI is more common in adults. 1p/19q deletions are uncommon in GTNI, only seen in a few cases with background oligodendroglioma. The prognosis is related to WHO grading. GTNI often recurs locally, and the prognosis is not good, especially in the spinal cord GTNI. The recommended treatment includes tumor resection combined with radiotherapy and chemotherapy.