Nervous system cancer cells. Fluorescent light micrograph of oligodendroglioma cells. Oligodendroglioma is a malignant (cancerous) tumour arising from oligodendrocytes. Oligodendrocytes are nerve cells that form the myelin sheath around neurons (nerve cells) in the central nervous system. The cells have been stained to show the enzyme galactosylceramidase (red) and membrane cofactor protein (CD46, green).