Pheochromocytoma

At a glance

Catecholamine-secreting tumor of chromaffin tissue (neuroectodermal origin), most commonly affecting the adrenal medulla (90% of patients), but may occur in any tissue derived embryologically from the neuroectoderm, including any sympathetic ganglia, the gastrointestinal tract, bladder, and thorax.

Synonym

Chromaffin Tumors.

Incidence

Estimated 2 to 8:1,000,000 (overall) of which 10% occur in children. It is the cause of 1 to 2% of systemic hypertension cases in the pediatric population. Compared to adults, children are more likely to present tumors that are bilateral, multiple, or extraadrenal in origin. Familial cases occur in more than 35% of all patients and are also more common in children and adolescents. It is more frequent in boys than in girls.

Genetic inheritance

Autosomal dominant inheritance in familial cases. Pheochromocytoma can be associated with ☞Neurofibromatosis Generalisata, ☞von Hippel-Lindau Syndrome, ☞Multiple Endocrine Neoplasia, ☞Tuberous Sclerosis, ☞Sturge-Weber Disease, or ☞Carney Complex (gastric leiomyosarcoma, pulmonary chondroma, and extraadrenal pheochromocytoma). Mutations have been identified in at least nine different genes: MAX, NF1, RET, SDHA, SDHB, SDHC, SDHD, VHL, and TMEM127.

Pathophysiology

Ninety percent of tumors are benign; multiple sites occur in approximately 35% of children and in 8% of adults. Epinephrine can only arise from the adrenal medulla, norepinephrine can arise from any sympathetic tissue. Elevated catecholamines cause an increase supraventricular rhythm, hypertension, and increased cardiac contractility and rate. Hyperglycemia may result from alpha-2 antagonism of insulin secretion. The catecholamines are metabolized by monoamine oxidase and catechol-O-methyltransferase, 5% of norepinephrine being excreted unchanged; urinary levels reflect plasma levels.

Diagnosis

History and examination, especially finding of paroxysmal or sustained hypertension at a young age. Demonstration of elevated urine catecholamine levels.

Clinical aspects

Triad of hypertension, headaches, and palpitations. Other symptoms include sweating, pallor, vomiting, weight loss, polyuria, polydipsia, and chest pain, which may be cardiac in origin. Examination reveals hypertension, which may be sustained or paroxysmal tachycardia, hypertensive retinopathy, and possibly signs of ventricular failure caused by dilated cardiomyopathy. The ECG may reveal dysrhythmia. In childhood, other catecholamine-secreting tumors, such as neuroblastoma, ganglioneuroblastoma, and ganglioneuroma, should be considered in the differential diagnosis. The tumor may be defined by ultrasonography, CT scan, or MRI scan. Laboratory investigations may reveal a raised hematocrit. Urinary vanillylmandelic acid (VMA) and metanephrines are elevated, as are plasma catecholamine levels. Extraadrenal sites of tumor should be excluded by metaiodobenzylguanidine (MIBG) uptake scan. In children, norepinephrine is usually the predominant catecholamine. In case of metastatic malignant tumor, therapeutic doses of MIBG are administered.

Precautions before anesthesia

Medical History: Inquire for symptoms of dysrhythmia or ventricular dysfunction. Catecholamine-induced cardiomyopathy is present in approximately 58% of patients. Cardiovascular assessment: ECG, echocardiography. ...