pineocytoma pineocytoma pineocytoma, is a benign, slowly growing tumor of the pineal gland. unlike the similar condition pineal gland cyst, it is uncommon. pineocytomaother namespinealocytomamicrograph of a pineocytoma. hps stain.specialtyoncology diagnosis pineocytomas are diagnosed from tissue, i.e. a brain biopsy.they consist of: cytologically benign cells (with nuclei of uniform size, regular nuclear membranes, and light chromatin) and, have the characteristic pineocytomatous/neurocytic rosettes, which is an irregular circular/flower-like arrangement of cells with a large meshwork of fibers (neuropil) at the centre. pineocytomatous/neurocytic rosettes are superficially similar to homer wright rosettes; however, they differ from homer wright rosettes as they have (1) more neuropil at centre of the rosette and, (2) the edge of neuropil meshwork irregular/undulating. management