Although pheochromocytoma is traditionally referred to as the “”10% tumor”" (10% being bilateral, malignant, extra-adrenal, hereditary, arising in children), in MEN2A patients, approximately 68% will have bilateral involvement with malignant disease occurring in 4% of cases [8]. Pheochromocytomas are rare, catecholamine secreting, yellowish-brown tumors composed of chromaffin AZD5363 ic50 cells derived from embryonic neural crest cells which were first described by Frankel [9] in 1886 in a young woman likely afflicted with MEN2 [10]. Hereditary

causes account for 20% of cases, while sporadic cases occur with an estimated prevalence of 0.95 per 100,000 adults per year [11]. In addition to MEN2, von Hippel Lindau Type 2, von Recklinghausen’s neurofibromatosis type 1, and familial paragangliomas are associated with the development of pheochromocytomas. Eighty percent of all pheochromocytomas arise within the adrenal medulla, while extra-adrenal lesions are most commonly found in the sympathetic ganglia as well as the organs of Zuckerkandl. Of note, it is estimated that 5% of adrenal incidentalomas are likely pheochromocytomas [12].

In addition to secreting the catecholes dopamine, epinephrine and norepinephrine, numerous other hormones have been isolated from pheochromocytomas including adrenocorticotropin, vasoactive intestinal peptide, neuropeptide Y, IL-6, calcitonin, and chromogranin A. Classically patients initially present with the triad of paroxysmal headaches, palpitations, and diaphoresis accompanied by marked hypertension. Of interest, it is estimated that pheochromocytomas are Histone Methyltransferase inhibitor present in 0.1-0.6% of patients Histamine H2 receptor with hypertension [13]. In addition to these symptoms, pallor, nausea, flushing, anxiety or a sense of doom, palpitations and abdominal pain can be part of the constellation of presenting symptoms. More ominously, patients may present in fulminant cardiogenic shock [14], multiorgan failure, or with acute hemorrhage.

Several biochemical assays are available to facilitate diagnosis, however, plasma free metanephrines had the highest sensitivity and urinary VMA had the highest specificity in a recent multicenter cohort trial [15] in the detection of pheochromocytomas. Once biochemical evidence of pheochromocytoma is obtained, imaging for localization should be undertaken to guide surgical resection. Computed tomography and magnetic resonance imaging provides high sensitivity for lesion detection, though poor specificity. Alternative imaging modalities such as I123 or I131 MIBG scintigraphy or PET may be utilized when CT or MRI fail to reveal the lesion or if malignancy is suspected. Although both Roux (Switzerland) and Mayo (US) are credited with concomitantly performing the first Seliciclib in vivo successful resections of pheochromocytomas in 1926, neither described any peri-operative hemodynamic instability, and both patients survived [16].