Granular cells in oligodendroglioma suggest a neoplastic change rather than a reactive phenomenon: case report with...

Oligodendrogliomas are diffuse gliomas characterised by IDH mutation and 1p/19q co-deletion. Classical oligodendrocytes, minigemistocytes, gliofibrillary oligodendrocytes, granular cells, and mucocytes are morphologic cell types described in oligodendroglioma. Even though the occurrence of granular cells in oligodendroglioma is known, exact nature of these cells and their molecular characteristics remain undetermined. We describe a case of oligodendroglioma with granular cells, in which we have attempted to molecularly characterise the granular cells. These granules were stained blue on Luxol fast blue and red on Masson's trichrome. The cells showed a distinct pattern of immunoreactivity to GFAP and IDH1. In addition, they exhibited mitotic activity and increased Ki-67 labelling. Molecularly, both the granular cells and classical oligodendroglial cells in the tumor showed 1p/19q co-deletion which is the diagnostic hallmark of an oligodendroglioma. Thus, we opine that granular cells are neoplastic and represent a morphological variant of neoplastic oligodendrocyte.