A malignant pheochromocytoma is a rare neuroendocrine tumour with an incidence of less than 1/million/year, often diagnosed in a late stage because of the atypical and indolent presentation and the lack of biochemical, morphological, genetic or histological predictors of malignancy.
We report a case of a 71-year-old woman with a mass in the right adrenal gland on abdominal ultrasound, performed for vague abdominal complaints. Computed tomography (CT) of abdomen and chest further differentiated the mass as having characteristics of malignancy and revealed multiple lesions in both lungs. A 24-hour urinary collection showed elevated metanephrines. A 68 gallium-DOTANOC-PET/CT-scan and 18F-FDG PET/CT-scan confirmed the suspicion of a malignant pheochromocytoma with lung metastases. The patient was treated by replacing the beta-blocker by an alpha-blocker to block the adrenergic spells. The adrenal tumour was resected, preceded by an embolization of the supplying arteries to prevent a catecholamine storm. Histology revealed large tumour with central necrosis and a fibrous capsule, capsular invasion was present. There were nests containing polygonal cells with large, hyperchromatic nuclei. There was a strong expression of antibodies against chromogranin and synaptophysin; S100 and vimentin staining were negative. The Pheochromocytoma of the Adrenal gland Scaled (PASS) Score was 3 (1 point for capsular invasion, 2 points for central necrosis). The metastases were monitored 3 months after the first evaluation with CT, which showed stable disease. A meta-iodobenzylguanidine scan (MIBG) didn’t show any uptake.
In a malignant pheochromocytoma, the degree of malignancy can only be determined by imaging. Additional imaging should be chosen with care, especially because standard 18F-FDG PET/CT has a lower sensitivity for detecting metastases than 68 gallium-DOTANOC-PET/CT. MIBG-capture is not always present in pheochromocytoma, which excludes MIBG therapy in progressive disease. Beta-blockers in monotherapy should be avoided because it could cause a hypertensive crisis caused by an alpha-1 mediated vasoconstriction. The cornerstone of treatment is resection, preferably of the primary tumour and all metastatic lesions. Our patient has inoperable lung metastases. In case of progressive disease, treatment options are peptide receptor radionuclide therapy (PRRT) and chemotherapy. Further follow-up is scheduled.