Familial occurrence of dysembryoplastic neuroepithelial tumor-like neoplasm of the septum pellucidum: case report.

OBJECTIVE: Dysembryoplastic neuroepithelial tumor (DNT)-like neoplasms of the septum pellucidum are extremely rare. In this article, we report the familial occurrence of these neoplasms. CLINICAL
PRESENTATION: We report two cases of such neoplasms: Patient 1, a 42-year-old woman, and Patient 2, the 20-year-old nephew of Patient 1. Patient 1 experienced headache and worsening dizziness; Patient 2 experienced headache and worsening dizziness and also had partial seizures. In both cases, magnetic resonance imaging (MRI) revealed an intraventricular tumor adjacent to the septum pellucidum. Both tumors appeared as a hypointense region on T1-weighted MRI, and both appeared as a hyperintense region on T2-weighted MRI without gadolinium enhancement. Interestingly, both tumors had a high apparent diffusion coefficient. INTERVENTION: Both tumors were subtotally removed and had common histological findings, such as alveolar structures with oligodendroglia-like cells and "specific glioneuronal element." These findings are consistent with a dysembryoplastic neuroepithelial tumor-like neoplasm. After tumor removal, the symptoms disappeared. The postoperative course was uneventful, and the patients did not require adjuvant therapy. MRI showed no regrowth of residual tumors at 4 years (Patient 1) and 2 years (Patient 2) postoperatively.
CONCLUSION: The familial occurrence of this rare tumor suggests that both of these cases arose from a common germline mutation. Identification of this rare tumor in this rare location is important to avoid unnecessary adjuvant therapy. A markedly high apparent diffusion coefficient and histological findings of specific glioneuronal element can facilitate the differential diagnosis of dysembryoplastic neuroepithelial tumor-like neoplasms. Genetic study of affected patients in this family may provide clues to its molecular pathogenesis.