RELA fusion-positive ependymoma accompanied by extensive desmoplasia: a case report.

We report a case of 33-year-old Japanese male who presented with a headache and visual disturbances. Magnetic resonance imaging revealed a large tumor in the left frontal lobe, measuring 7 cm in diameter, which was diagnosed as supratentorial anaplastic ependymoma accompanied by extensive desmoplasia. The patient underwent a gross total resection. Histologically, the tumor cells had oval or short, spindle-shaped nuclei, and proliferating cells in perivascular pseudorosettes with anucleate zones and mitotic figures. Desmoplasia with abundant collagen fibers among the tumor cells was detected at numerous sites, and perinuclear dot- or ring-like immunoreactivity for epithelial membrane antigen was identified. Five years and six months after the initial procedure, a small recurrent tumor was identified at the removal site. The patient underwent a second total resection. The histology of the resected tumor showed decreased collagen production and more apparent anaplastic features as compared to those of the initial tumor. In addition to the histological findings, molecular examinations revealed ependymoma, RELA fusion positive. Although not commonly observed, this case suggests that desmoplasia could be associated with ependymomas, including RELA fusion-positive variant. Moreover, our findings indicate that high-grade ependymoma requires careful, long-term follow-up even if gross total resection is performed.