<P> These tumors can form a pattern with other endocrine gland cancers which is labeled multiple endocrine neoplasia (MEN). Pheochromocytoma may occur in patients with MEN 2 and MEN 3 (MEN 2B). Von Hippel Lindau patients may also develop these tumors . </P> <P> Patients experiencing symptoms associated with pheochromocytoma should be aware that it is rare . However, it often goes undiagnosed until autopsy; therefore patients might wisely choose to take steps to provide a physician with important clues, such as recording whether blood pressure changes significantly during episodes of apparent anxiety . </P> <Ul> <Li> Blood tests: Buters and others have suggested that analysis of free metanephrines (metadrenalines) (normetanephrine and metanephrine) in blood plasma is the most accurate test for detecting pheochromocytoma . </Li> <Li> Urine tests: Although this test is slightly less effective than plasma testing it is still considered highly effective in diagnosis . Usually the metabolites of norepinephrine and epinephrine, normetanephrine (NMN) and metanephrine (MN), are found in relatively small amounts in normal humans . The increased excretion of these metabolites is indicative of the disease, but does not completely rule out other diseases which may cause the same excretion values . </Li> <Li> Other Tests: </Li> </Ul> <Li> Blood tests: Buters and others have suggested that analysis of free metanephrines (metadrenalines) (normetanephrine and metanephrine) in blood plasma is the most accurate test for detecting pheochromocytoma . </Li>

List the histological features that give rise to pheochromocytomas