Familial pheochromocytoma

Abstract

Pheochromocytomas and Paragangliomas (PGL) form the group of paraganglial tumours which can occur in any paraganglia from the skull base to the pelvic floor. The terminology is not uniform. While the World Health Organization (WHO) applies pheochromocytoma exclusively to adrenal tumours, many clinicians use the term pheochromocytoma also for extra-adrenal abdominal and thoracic tumours, since by tradition pheochromocytoma is a vasoactive tumour. In contrast, head and neck paraganglioma is mostly only a space-occupying mass. The diagnosis is confirmed by both biochemical testing and radiological imaging. One third of patients with pheochromocytomas and paragangliomas are carriers of germline mutations in one of 6 genes and thus have a hereditary disorder. About 1% of Neurofibromatosis (NF) 1 patients have pheochromocytomas. All pheochromocytoma patients with NF 1 also show cutaneous lesions. About 50% of MEN2 patients harbour pheochromocytoma. The dominant lesion in this entity is Medullary Thyroid Carcinoma (MTC) occurring in up to 100% of patients. Von Hippel-Lindau disease (VHL)is found in about 20% of patients in association with pheochromocytoma. VHL is classified as type 1 predominantly without and type 2 predominantly with pheochromocytoma. Other important components of VHL are hemangioblastomas of the eye and Central Nervous System (CNS), renal clear cell carcinoma, multiple pancreatic cysts and islet cell carcinoma. PGL syndromes have been genetically characterized as PGL 1, 3 and 4 and are caused by mutations in the succinate dehydrogenase (SDH) subunit D, C and B genes, respectively (SDHD, SDHC and SDHB). Paraganglioma syndromes include predisposition to paraganglial tumours in any location, whereas PGL 3 patients mostly show only head and neck paragangliomas. All syndromes associated with paraganglial tumours are autosomal dominantly transmitted, but patients with SDHD mutations develop tumours only if they inherit the mutation from the father. Familial paraganglial tumours are characterized by younger age at diagnosis and more frequently multifocal and extra-adrenal abdominal pheochromocytomas. Patients with PGL 4 and less frequently VHL, are particularly predisposed to malignant pheochromocytoma. Endoscopic surgery is the primary treatment for pheochromocytoma. For malignant cases, chemotherapeutic as well as radionuclear approaches are available. No specific treatment has been proposed for prevention of the disease in inherited disorders. Thus, early diagnosis and regular follow-up are the only means for a better outcome.