Malignant transformation of a dysembryoplastic neuroepithelial tumor verified by a shared copy number gain of the tyrosine kinase domain of FGFR1.

Abstract

Dysembryoplastic neuroepithelial tumors (DNTs) are regarded as benign glioneuronal neoplasms because of their excellent outcomes; however, rare DNTs show malignant transformation. We herein described a case of DNT showing malignant transformation. The patient had intractable epilepsy caused by a tumor at 1year of age and partial resection was performed. After surgery, the residual tumor showed regrowth and surgery was performed again at 4years of age. The resected tumor showed the typical histological features of DNT, such as specific glioneuronal elements and alveolar structures. Tumor regrowth was detected again at 6years of age, and the patient underwent gross total resection. Histologically, the tumor was composed of a high-grade glial component mixed with atypical neuronal cells, and the diagnosis of an anaplastic glioneuronal tumor was made. Genetically, DNT and the anaplastic glioneuronal tumor both shared a copy number gain of the tyrosine kinase domain of fibroblast growth factor receptor 1 (FGFR1), as demonstrated by multiplex ligation-dependent probe amplification (MLPA), corresponding to internal tandem duplication (ITD). A frequent FGFR1-ITD in DNT was previously reported. To the best of our knowledge, an identical mutation between primary and transformed DNT has not yet been demonstrated by MLPA.