Since the first description by Kepes in 1979, the diagnosis of PXAs should comply with a few criteria such as: 1) highly pleomorphic tumor cells, 2) presence of lipid-laden, foamy, or "xanthomatous" tumor cells, 3) absence of necrosis, 4) rare or no mitoses, 5) GFAP positivity in some tumor cells, and 6) rich pericellular or stromal reticulin staining [32]. This evidence concerns the gene GFAP and neoplasm.