Table 7. Characteristics of Paraganglioma (PGL) and Pheochromocytoma (PCC) Associated with Susceptibility Genesa continued...
Immunohistochemical SDHB staining may help triage genetic testing; tumors of patients with SDHB, SDHC, and SDHD mutations have absent or very weak staining, while sporadic tumors and those associated with other constitutional syndromes have positive staining.[47,48] Therefore, immunohistochemical SDHB staining can help identify potential carriers of a SDH mutation early, thus obviating the need for extensive and costly testing of other genes.
Patients with pheochromocytoma and sympathetic extra-adrenal paraganglioma usually present with symptoms of excess catecholamine production, including hypertension, headache, perspiration, palpitations, tremor, and facial pallor. These symptoms are often paroxysmal, although sustained hypertension between paroxysmal episodes occurs in more than one-half the patients. These symptoms can also be induced by exertion, trauma, labor and delivery, induction of anesthesia, surgery of the tumor, foods high in tyramine (e.g., red wine, chocolate, cheese), or urination (in cases of primary tumor of the bladder). Parasympathetic extra-adrenal paragangliomas do not secrete catecholamines and usually present as a neck mass with symptoms related to compression, but also may be asymptomatic and diagnosed incidentally.
Paraganglioma and pheochromocytoma in children and adolescents
Paraganglioma and pheochromocytoma are exceedingly rare in the pediatric and adolescent population, accounting for only approximately 20% of all cases.[49,50]
Younger patients have a higher incidence of bilateral adrenal pheochromocytoma and extra-adrenal paraganglioma, and a germline mutation can be identified in close to 60% of patients. Therefore, genetic counseling and testing is always recommended in young patients. The pediatric and adolescent patient appears to present with symptoms similar to those of the adult patient, although with a more frequent occurrence of sustained hypertension. The clinical behavior of paraganglioma and pheochromocytoma appears to be more aggressive in children and adolescents and metastatic rates of up to 50% have been reported.[41,50,51]
In a study of 49 patients younger than 20 years with a paraganglioma or pheochromocytoma, 39 (79%) had an underlying germline mutation that involved the SDHB (n = 27; 55%), SDHD (n = 4; 8%), VHL (n = 6; 12%), or NF1 (n = 2; 4%) genes. The germline mutation rates for patients with nonmetastatic disease were lower than those observed in patients who had evidence of metastases (64% vs. 87.5%). Furthermore, among patients with metastatic disease, the incidence of SDHB mutations was very high (72%) and most presented with disease in the retroperitoneum; five died of their disease. All patients with SDHD mutations had head and neck primary tumors. In another study, the incidence of germline mutations involving RET, VHL, SDHD and SDHB in patients with nonsyndromic paraganglioma was 70% for patients younger than 10 years and 51% among those aged 10 to 20 years. In contrast, only 16% of patients older than 20 years had an identifiable mutation. It is important to remember that these two studies did not include systematic screening for other genes that have been recently described in paraganglioma and pheochromocytoma syndromes such as KIF1B-beta, EGLN1/PHD2, TMEM127, SDHA, and MAX (see Table 7).