Angiosarcoma was ruled out mainly based on the diffuse positivity for the neuroendocrine markers (chromogranin, synaptophysin, S-100 protein, and CD56) together with a negative cytokeratin reaction (SMA) and, most importantly, a positivity for CD56 (7), thus arriving at the final diagnosis of retroperitoneal paraganglioma. This evidence concerns the gene SYP and angiosarcoma.