Pheochromocytomas and extra-adrenal paragangliomas detected by screening in patients with SDHD-associated head-and-neck paragangliomas.

Patients with SDHD-associated head-and-neck paragangliomas (HNP) are at risk for developing pheochromocytomas for which screening has been advised. To assess clinical, biochemical, and radiological outcomes of screening in a large single-center cohort of SDHD-positive patients with HNP and to address the necessity for repetitive follow-up, we evaluated 93 patients with SDHD-associated HNP (p.Asp92Tyr, p.Leu139Pro). Screening consisted of measurement of 24 h urinary excretion of catecholamines and/or their metabolites in duplicate, which was repeated with intervals of 2 years if initial biochemical screening was negative. In patients, in whom urinary excretion was above the reference limit, imaging studies with (123)I-MIBG (metaiodobenzylguanidine) scintigraphy and magnetic resonance imaging (MRI) and/or computed tomography (CT) were performed. Pheochromocytomas and extra-adrenal paragangliomas were treated surgically after appropriate blockade. Median follow-up was 4.5 years (range 0.5-19.5 years). Twenty-eight out of the 93 patients were included in our study and underwent additional imaging for pheochromocytomas/extra-adrenal paragangliomas. In 11 out of the 28 patients intra-adrenal pheochromocytomas were found. Extra-adrenal paragangliomas were discovered in eight patients. These tumors were detected during initial screening in 63% of cases, whereas 37% were detected after repeated biochemical screening. One patient was diagnosed with a biochemically silent pheochromocytoma. The high prevalence of pheochromocytomas/extra-adrenal paragangliomas in patients with SDHD-associated HNP warrants regular screening for tumors in these patients. Paragangliomas that do not secrete catecholamines might be more prevalent than previously reported. Future studies will have to establish whether routine imaging studies should be included in the screening of SDHD mutation carriers, irrespective of biochemical screening.