IUHS Student-2-Student USMLE Step 1 Recall
Endocrinology
Adrenal Medulla
Normal Adrenal Medulla
it is composed of specialized
neural crest (neuroendocrine) cells, termed chromaffin cells, and their supporting (sustentacular) cells...the chromaffin cells are round-to-oval, have prominent cytoplasmic membrane bound granules of stored catecholamines, and are supported by a richly vascularized scant stroma of spindled and sustentacular cells...these cells, so named b/c of their brown-black color after exposure to potassium dichromate (zenker), synthesize and secrete catecholamines in response to signals from preganglionic nerve fibers in the sympathetic nervous system...
the
adrenal medulla is the major source of catecholamines - epinephrine, norepinephrine - in the body...norepinephrine functions as a local neurotransmitter, chiefly of sympathetic postganglionic neurons...only small amounts reach the circulation...epinephrine (adrenaline) is secrted into the vascular system...Pheochromocytomas
90%
have sustained hypertension...pheochromocytomas are uncommon neoplasms composed of chromaffin cells, which
synthesize and release catecholamines and in some instances peptide hormones...
these tumors are important b/c they (similar to aldosterone-secreting adenomas)
give rise to surgically correctable forms of hypertension...although only about .1 to .3% of hypertensive patients have an underlying pheochromocytoma goes unrecognized...occasionally, one of these tumors produces other steroids or peptides and so may be associated with cushing syndrome or some other endocrinopathy...about
85% of pheochromocytomas arise in the medulla of the adrenals, the remainder in any of the extra-adrenal paraganglia, more often below the diaphragm....extra-adrenal tumors that are chromaffin negative are sometimes called paragangliomas to differentiate them from functioning pheochromocytomas...although 90% of pheochromocytomas occur sporadically, about 10% occur in one of the several, mostly autosomal dominant, familial sydromes...these include the MEN syndromes, type I neurofibromatosis, von Hippel-Lindau disease, and Sturge-Weber syndrome...
although the nonfamilial pheochromocytomas most often occur in adults between 40-60 years of age, with a slight female proponderance, in the familial syndromes many arise in childhood, with a strong male preponderance...most tumors in the
famililar syndromes are bilateral (70%), but in the nonfamilial setting only 10-15% are bilateral...
incubation of fresh tissue with a
potassium dichromate solution turns the tumor a dark brown color owing to oxidation of stored catecholamines, thus the term chromaffin...the histologic pattern in pheochromocytoma is quite variable...the tumors are composed of
polygonal to spindle-shaped chromaffin cells, clustered with their supporting cells into small nests of alveoli (zellballen), by a rich vascular network...uncommonly the
dominant cell type is a spindle or small cell...various patterns can be found in any one tumor...the cytoplasm has a finely granular appearance, best demonstrated with silver stains, owing to the appearance of granules containing catecholamines...mitotic figures are rare and do not imply malignancy...both capsular and vascular invasion may be encountered in benign lesions...therefore the
diagnosis of malignancy in pheochromocytomas is based exclusively on the presence of metastases...90%
have sustained hypertension...5-10% are malignant...vanillylmandelic acid (VMA)
is found in the urine...the dominant clinical feature in patients with pheochromocytoma is
Hypertension and Hyperglycemia...classically this is described as an abrupt, precipitous elevation in blood pressure, associated with tachycardia, palpitations, headache, sweating, tremor, and a sense of apprehension...these episodes may also be associated with
pain in the abdomen or chest, nausea, and vomiting...in practice, isolated paroxysmal episodes of hypertension occur in less than half of patients...in about two thirds of patients, the hypertension occurs in the form of chronic, sustained elevation in blood pressure, although an element of labile hypertension is also present...the
paroxysms may be precipitated by emotional stress, exercise, changes in posture, and palpation in the region of the tumor...the elevations of pressure are
induced by the sudden release of catecholamines that may acutely precipitate congestive heart failure, pulmonary edema, MI, ventricular fibrillation, and cerebrovascular accidents...the cardiac complications have been attributed to what has been called catechloamine cardiomyopathy, or catecholmaine induced myocardial instability and ventricular arrhythmias...the myocardial changes have been attributed to ischemic damage secondary to the catecholamine induced vasomotor constriction of the myocardial circulation or to direct toxicity...The biogenic amines contained in the cells of a pheochromocytoma of the adrenal gland are stored in
neurosecretory granules...the laboratory diagnosis of pheochromocytoma is based on the demonstration of
increased urinary excretion of free catecholamines and their metabolites, such as vanillylmandelic acid (VMA) and metanephrines...Neuroblastoma (Wilms tumor)
neuroblastoma,
one of the most common childhood tumors.These tumors produce catecholamine precursors such as
vanillylmandelic acid (VMA) and homovanillic acid (HVA) in small amounts, so hypertension is unusual...retroperitoneum adjacent to the kidney and displacing the kidney...
abdomen distended
...baby has not been feeding well
...below the expected weight for his age
...n-myc
is associated with neuroblastoma...Wilms Tumor
...