CHAPTER 32 Adrenal Tumors
How often are adrenal masses incidentally detected on CT scans?
5% of the time.
What is the relationship between age and the incidence of adrenal incidentalomas?
The incidence for adrenal incidentalomas increases with age, with 0.5% incidence during the 3rd decade of life and 7% incidence during the 8th decade of life.
What percentage of adrenal incidentalomas will be deemed potential surgical lesions upon further evaluation?
20%
What are the 2 general questions one needs to answer when working up an adrenal mass?
1. Whether it is functional or nonfunctional.
2. Whether it is benign or malignant.
What is the differential diagnosis of a benign incidental adrenal mass?
The more common adrenal lesions are adrenal adenomas, myelolipomas, and adrenal cysts. Less commonly one encounters ectopic tissue, oncocytomas, ganglioneuromas, pheochromocytomas, aldosteronomas, and adrenal hemorrhage.
List 4 pathologic conditions associated with hypersecretion of adrenal products.
Pheochromocytoma, Cushing syndrome, primary aldosteronism, and adrenal carcinoma.
How does adrenal hemorrhage following birth occur and which side is affected more often?
Adrenal hemorrhage can occur following difficult childbirth and more often affects the right side. This phenomenon has been attributed to an increase in intra-abdominal pressure that is transmitted through the short right adrenal vein and into the parenchyma resulting in hemorrhage.
What are the 2 most common adrenal lesions detected incidentally?
Adenomas (75%) and myelolipomas (6%).
What is the differential diagnosis of a malignant adrenal mass?
Adrenocortical carcinoma, pheochromocytoma, neuroblastoma, and metastatic disease.
What percentage of patients with an incidental adrenal mass will be diagnosed with pheochromocytoma?
Approximately 5%.
What percentage of pheochromocytomas will arise outside of the adrenal gland?
10% to 25% of pheochromocytomas will be extra-adrenal.
List the symptoms of pheochromocytoma.
Headache, palpitations, sweating, pallor, flushing, weight loss, fatigue, anxiety, hypertension, and hyperglycemia.
What is the 10% rule regarding pheochromocytomas?
10% of pheochromocytomas are malignant, 10% are bilateral, 10% are found in the pediatric age group, 10% will be extra-adrenal, and 10% are associated with multiple endocrine neoplasia (MEN) syndrome.
How accurate is the 10% rule in contemporary series evaluating pheochromocytomas?
The classic 10% rule for pheochromocytomas does not seem to reflect contemporary findings. In more recent series up to 25% will be extra-adrenal, up to 30% will be associated with a hereditary syndrome, and malignant disease will be seen in only 5% of cases.
List the hereditary conditions associated with pheochromocytoma.
Multiple endocrine neoplasia type 2a, multiple endocrine neoplasia 2b, von Hippel–Lindau syndrome, neurofibromatosis type 1, familial paraganglioma syndrome type 4, and familial paraganglioma syndrome type 1.
When is a partial adrenalectomy indicated?
In patients with bilateral and hereditary adrenal tumors.
Is the pattern of hypertension with pheochromocytomas sustained or paroxysmal?
Sustained hypertension is found in 50% to 60% of patients, and is a more common finding in children and patients with multiple endocrine adenoma type-2 (MEA-2). Paroxysmal hypertension affects approximately 30% of patients. Orthostatic hypotension can be noted in 10% to 50% of patients.
Is it possible to have a pheochromocytoma in a normotensive patient?
Yes. Approximately 10% of pheochromocytomas are found in normotensive patients. This is why it is important not to eliminate pheochromocytomas from your differential diagnosis in a normotensive patient with an adrenal mass.
How do the manifestations of pheochromocytoma in children vary from those in adults?
Children manifest a higher incidence of familial pheochromocytomas (10%) and bilaterality (25%). Additionally, there is a 15% to 30% incidence of multiple pheochromocytomas in children and a 15% to 30% incidence of extra-adrenal location as well.
What are the most common locations for extra-adrenal pheochromocytomas?
The organ of Zuckerkandl (close to the origin of the inferior mesenteric artery), bladder wall, heart, mediastinum, carotid, and glomus jugulare bodies.
What symptom is classically associated with extra-adrenal pheochromocytoma involving the urinary bladder?
Micturition syncope.
What laboratory tests confirm the diagnosis of pheochromocytoma?
Free-fractionated plasma metanephrines and 24-hour urinary-fractionated metanephrine tests are the recommended studies to screen for and diagnosis pheochromocytoma.
What is the utility of CT scanning for detecting pheochromocytomas?
CT scanning detects >90% of pheochromocytomas of adrenal origin, and approximately 75% of extra-adrenal pheochromocytomas. Computed tomography alone cannot differentiate between pheochromocytomas and other adrenal lesions nor can one delineate malignant potential based upon the CT scanning alone.
What is the average Hounsfield units of pheochromocytoma on unenhanced CT scans?
35 Hounsfield units.
What clinical, biochemical, and histologic features distinguish malignant from benign pheochromocytomas?
Malignancy can be suggested by large tumor size, DNA ploidy pattern, local invasion, but is defined by the presence of metastases.
What are the most common sites of metastatic pheochromocytoma?
Bone, lung, liver, and lymph nodes.
What is the characteristic appearance of pheochromocytoma on MRI scanning?
They appear as a characteristically bright image on T2-weighted studies, but the diagnosis cannot be based upon MRI alone.
What is an MIBG scan, what does “MIBG” stand for, and how is it useful?
The metaiodobenzylguanidine (MIBG) scan images adrenal medullary tissue and is particularly useful for identifying pheochromocytomas of extra-adrenal origin or multiple pheochromocytomas. The MIBG scan has an overall sensitivity and specificity of 87% and 99%, respectively. The false-negative rate is 10%.
What is the preoperative medical preparation for patients with pheochromocytomas?
All patients must be vigorously hydrated in preparation for surgery since elevated catecholamine levels lead to significant dehydration. Additionally, patients are started on an α-adrenergic blocker such as phenoxybenzamine, with an initial divided dose of 20 to 30 mg orally, increasing to 40 to 100 mg as needed. Secondly, β-adrenergic blockers can be added to the α-blockers to protect against arrhythmias and permit reduction in the a-blocker requirement. β-Blockers are usually only added when cardiac arrhythmias are identified. Labetalol (Normodyne) is a nonselective β-blocker and a selective α-adrenergic blocker that has been shown to control hypertension associated with pheochromocytoma. Calcium channel blockers may also be utilized for controlling hypertension associated with pheochromocytoma.
What problem can arise if β-blockers are initiated prior to α-blockers?
There can be a marked rise in the total peripheral vascular resistance secondary to unopposed α-adrenergic activity that can lead to circulatory collapse.
What additional drug might be used in the preoperative preparation of patients with pheochromocytomas who have cardiomyopathies, multiple catecholamine-secreting paragangliomas, or resistance to α-blockers?
α-Methylparatyrosine (metyrosine) decreases the rate of catecholamine synthesis (the conversion of tyrosine to dopa).
How should the surgeon and anesthesiologist be prepared for fluctuations in blood pressure at the onset of anesthetic induction in surgery?
The patient must be volume-expanded with several liters of intravenous crystalloid prior to induction of anesthesia. In addition, α- and β-adrenergic blocking agents should be readily available for IV use. Phentolamine, a short-acting α-blocker (50 mg per 500 mL of ringers lactate), or sodium nitroprusside (50 mg per 250 mL of 5% dextrose in H2O) should be on hand. Esmolol or propranolol should be available for persistent tachycardias or arrhythmias.
What are the indications, advantages, and disadvantages for using a modified posterior incision for adrenal tumors?
A modified posterior lumbotomy may be utilized in patients with right-sided adrenal aldosterone-secreting tumors or benign adenomas <5 cm. The main advantage over a flank or transabdominal incision is the excellent exposure of the vena cava in the region of the short right adrenal vein. The disadvantages include a limited visual field and compression of the abdominal contents and thoracic cavity that may impair respirations in the jackknife position. This approach is not recommended for pheochromocytomas or malignant adrenal tumors.
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