Malignant Phaeochromocytoma

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Incidence and Pathology

The incidence of phaeochromocytoma is approximately 1-2 cases per 100,000 population. Malignant phaeochromo-cytomas accounts for only 10% of all phaeochromocytomas but in extra-adrenal tumours, located along the course of the sympathetic chain the incidence of malignancy rises to 40-50% (116). There is a higher incidence of extra-adrenal tumours in children compared with adults.

Tumours are usually cystic with areas of haemorrhage and necrosis. Vascular invasion is a histological feature of phaeochromocytomas seen in benign as well as malignant tumours. Diagnosis of malignancy is therefore difficult and may only be confirmed by establishing the presence of distant spread.

Localisation

Recurrence or persistence of symptoms in patients who have previously undergone surgery for phaeochromo-cytoma may indicate malignancy. Symptoms include hypertension (sustained or paroxysmal), headaches and palpitations. Recurrent or distant metastatic disease may be confirmed by measuring urinary catecholamines and metabolites (metanephrines and vanillyl mandelic acid) levels in an acidified 24 hour collection.

MRJ, which has a characteristic signal in phaeochromocytoma, is the best method of identifying recurrent local disease (117). Distant disease may also be identified by MIBG scan, though this has a false negative rate of approximately 10% (116).

Treatment of Recurrent or Distant Malignant Phaeochromocytoma

Recurrent disease should be resected when ever feasible. has been shown to have a therapeutic as well as diagnostic role but treatment is palliative (118). Chemotherapy using combination cyclophosphamide, vincristine and dacarbazine has produced a partial response in controlling symptoms in 57% of patients but overall results are disappointing (119). Radiotherapy can be employed to control pain from bone metastases (120). Symptoms of catecholamine excess may to some extent be alleviated by combination therapy with alpha and beta blocking agents with or without an agent which inhibits catecholamine secretion.

Treatment of hypertension by conventional antihypertensives will also be appropriate when there is persistent metastatic disease.

Prognosis

Five year survival rates in malignant phaeochromocytoma are 35-40% with extra adrenal tumours carrying a less favourable prognosis (121).

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