<prompt> Which of the following criteria can be used to determine if a pheochromocytoma lesion is benign or malignantBlood vessel invasionCannot be determined by microscopic examinationHemorrhagic and necrosisNuclear pleomorphism  <response>: Ref Robbins 8e p1159-1161;9e p1135 Pheochromocytoma and their related counterpas in extra adrenal sites called paraganglioma, are notorious Because the only reliable indicator of metastasis potential is the presence of distant metastasis . Very malignant appearing tumors may not metastasize and benign appearing tumors may produces metastases . These tumors should all be considered potentially malignant . 