|Micrograph of a pineocytoma. HPS stain.|
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.
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