Anaplastic changes of diffuse leptomeningeal glioneuronal tumor with polar spongioblastoma pattern.

Diffuse leptomeningeal glioneuronal tumor (DLGNT) is a rare glioneuronal neoplasm with oligodendroglioma-like cells confined in the subarachnoid spaces. A great majority of DLGNT are histologically low grade. However, some tumors show features of anaplasia with increased mitotic and proliferative activity. Due to the limited number of patients and inadequate clinical follow-up reported to date, the WHO classification does not yet assign a distinct WHO grade to this entity. Polar spongioblastoma pattern, in which bipolar cells are arranged in parallel with palisading nuclei, remains poorly understood about the pathological process of forming this pattern. We experienced a case of 22-year-old man developing DLGNT with extensively distributed anaplastic changes involving polar spongioblastoma pattern and the secondary tumor invasion to brain parenchyma in 4½ years before the autopsy. Clinical and pathological courses of the patient are presented with radiological, histopathological, and genetic examinations. This is the first report demonstrating the immunohistological and genetic evaluation of a DLGNT with polar spongioblastoma pattern.