Cerebellar high-grade astrocytoma with IDH mutations in the elderly: A report of two cases.

Cerebellar high-grade gliomas are rare, and likely to affect younger patients compared with those of cerebral origin. Recent genetic analyses have revealed that isocitrate dehydrogenase (IDH) 1/2 mutations are rare in infratentorial gliomas. In this paper, we report two elderly cases of IDH-mutated cerebellar high-grade glioma with unusual histological features and uncommon patient ages. One case was an 83-year-old man, whose tumor was predominantly composed of densely packed round-to-polygonal epithelioid cells. The other was a 75-year-old woman's high-grade astrocytoma characterized by cord-like structures and the perivascular papillary arrangements with varying amounts of myxoid matrix. The former harbored IDH1 R132H mutation, whereas the latter had IDH2 R172K mutation. According to our literature review, eight cases of IDH-mutated infratentorial gliomas including the present cases have been reported, and four had mutations other than IDH1 R132H. Moreover, we herein report the first elderly case of IDH2-mutation. Although the number is limited, IDH-mutant infratentorial diffuse gliomas may have clinical, histological and genetic features different from supratentorial cases.