Atypical teratoid/rhabdoid tumor evolving from an optic pathway ganglioglioma: case study

Abstract

We report an atypical teratoid/rhabdoid tumor arising in a ganglioglioma from an 11-year-old male who had been treated over a nine-year period. A combined histologic, immunohistochemical, and molecular genetic analysis confirmed this diagnosis. Molecular genetic studies demonstrated a mutation in exon 9 of the INI1 gene in the tumor, which was not present in the patient's blood. This report is the first to describe progression of a ganglioglioma to atypical teratoid/rhabdoid tumor.

Fig. 1

Recurrent tumor. Regions of tumor with low-grade features had the typical appearance of ganglioglioma with distinct areas showing the glial component with abundant fibrillary neoplastic neuropil (A) as well as areas with numerous atypical neoplastic ganglion cells (arrowhead, B). In other areas, the tumor showed high-grade features and was made up of small cells with distinct cell borders, abundant eosinophilic cytoplasm, and large nuclei with vesicular chromatin and prominent nucleoli (C). Immunohistochemical staining for INI1 demonstrated a loss of nuclear expression throughout areas with high-grade rhabdoid features (D, left side) but retained expression in areas with ganglioglioma features (right side).

Fig. 2

A single base pair deletion within exon 9 of the INI1 gene was detected in the tumor tissue, but not in peripheral blood DNA. The deletion causes a frameshift, which is likely to result in an unstable message or protein.