Intrathoracic phaeochromocytoma

A 21-year -old lady presented with hypertension and a posterior mediastinal mass and raised urinary catecholamines.

A 21-year-old lady presented with hypertension which was difficult to control. She had blood and urine tests. Routine blood tests were normal. Renin/aldosterone were within normal limits. Tests for auto-immune tests were normal. Urine catecholamines were raised and a repeat test performed which too showed raised levels consistent with paeochromocytoma. ( Noradrenaline= 12.4, dopamine 3.39, HMMA 64 and HVA 9: all in micromol/spec). A chest x-ray showed a posterior mediastinal mass. CT, MRI and isotope scanning were performed. These were suggestive of phaeochromocytoma and the mass was operated upon.The histology was that of an extra-adrenal paraganglioma/pheochromocytoma.

The patient remains asymptomatic at follow-up. The raised levels of catecholamines in the urine returned to normal levels after surgery.

Phaeochromocytoma is a rare but important endocrine tumour. Clinical and biochemical manifestations are mainly caused by excess circulating catecholamines and hypertension. Manifestations mimic many conditions, which may result in erroneous diagnosis and improper treatment.

Sustained or paroxysmal hypertension associated with headaches, sweating, or palpitations, occurs in 95% of patients, but at least 5% are normotensive. All patients with manifestations of hypercatecholaminaemia or coexisting neoplasm should be investigated for phaeochromocytoma.

The diagnosis is made by finding raised plasma norepinephrine/epinephrine and/or raised urinary catecholamine. Plasma free metanephrines provide the best test for excluding or confirming phaeochromocytoma and should be the test of first choice for diagnosis of the tumour. The pentolinium suppression test (which does not affect an autonomous adrenal medullary tumour) is also diagnostic, but is considered dangerous.

Phaeochromocytomas are usually large (some weighing as much as 4kg), but are occasionally only 3-5mm in diameter. Ten percent of tumours are extra-adrenal, 10% multiple and 10% malignant. Nearly 95% are within the abdomen. Many studies report a higher rate of malignancy for extra-adrenal phaeochromocytomas than for adrenal phaeochromocytomas. A recent paper by Goldstein et al. suggests that patients with extra-adrenal phaeochromocytomas have the same risk of malignancy and the same overall survival as patients with adrenal phaeochromocytomas. The commonest sites for extra-adrenal tumours are the renal hilum and the organ of Zuckerkandl. The tumour may be familial in Sipple's syndrome or MEN IIA and MEN IIB and is also associated with neurofibromatosis in 5% of cases. It may also be associated with tuberous sclerosis and von Hippel-Lindau syndrome.

Ultrasound can show these tumours if they are large and is the modality of choice in children. In adults, CT is the ideal imaging modality. Intravenous contrast enhancement is important.This may show uniform enhancement, rim enhancement being seen in tumours with necrosis. Hyperplastic adrenals show generalised enlargement with preservation of normal glandular configuration. A phaeochromocytoma is of mixed attenuation, and 7% show calcification. Peripheral enhancement is seen and there are central non-enhancing areas caused by tumour necrosis. MR is reserved for equivocal cases, and is particularly useful in the detection of extra-adrenal phaeochromocytomas. 123I-MIBG (meta-iodobenzylguanidine) will concentrate in phaeochromocytoma and is therefore of use in locating extra-adrenal tumours. Arteriography and venous sampling have both been used in localisation of extra-adrenal phaeochromocytomas. 18F DOPA PET scans have been used recently and appear a highly sensitive and specific biochemical imaging approach for detection of pheochromocytomas.

Surgical resection is successful in 90% of cases, but 10% of tumours are malignant. Phaeochromocytomas less than 5cm in diameter can be removed laparoscopically; larger tumours should be removed by open surgery. Currently, pheochromocytoma removal is a safe operation with mortality rates ranging from 0 to less than 3%. Preoperative alpha-adrenergic blockage with phenoxybenzamine or prazosin is important in decreasing the operative risk. Beta-blockers may be necessary for cardiac arrhythmia. Drug treatment prior to and during surgery is mandatory. Drug treatment, chemotherapy and radiation therapy are used to treat malignant lesions. Lifelong follow-up for patients with phaeochromocytoma is important.