![]() The rich genetic background of these tumours, which is even found in 12% of apparently sporadic PPGLs, has led to recommendations that every patient with PPGL should be considered for genetic testing. Among these, hereditary PPGL is the most common condition and is mostly caused by germline mutations in the SDHB, SDHC, or SDHD genes. Although a sporadic form exists, the vast majority of PPGLs occur as a manifestation of inherited tumour syndromes such as multiple endocrine neoplasia type 2 (MEN2 RET gene), von Hippel–Lindau (VHL) disease ( VHL gene), neurofibromatosis type 1 (NF1 NF1 gene), and hereditary PPGL. Rather, PPGL shows the highest degree of heritability in human neoplasms, up to 40%. The classical “rule of 10”, which states that 10% of these tumours are associated with a familial syndrome, has been invalidated recently. Pheochromocytomas and sympathetic paragangliomas (PPGLs) are rare catecholamine-secreting tumours arising from chromaffin tissue of the adrenal medulla or extra-adrenal sympathetic paraganglia. However, in the case of weakly positive SDHB staining, an additional gene study should be considered. In conclusion, SDHB-negative IHC is a cost-effective and reliable method to predict SDHx mutations. Six patients with weakly positive SDHB IHC with primarily unknown genetic status were re-called and underwent next-generation sequencing. There were no SDHx mutations in the SDHB-positive IHC group. The genetic test results of patients with SDHB-weakly positive IHC varied (one SDHB, two RET, one VHL, and three unknown gene mutations). All 10 patients with SDHB-negative IHC contained SDHB or SDHD mutations. ![]() ![]() Tissue microarrays (TMAs) were constructed with PPGL tissues and IHC for SDHB was performed on TMA sections. In total, 52 patients who underwent surgery for PPGL treatment between 20 and underwent genetic analysis at diagnosis were included. Given the fact that the immunohistochemistry (IHC) result for SDHB is always negative regardless of the type of SDHx mutation, we aimed to evaluate the efficacy of using SDHB IHC for screening SDHx mutations in PPGL cases. The most common genetic backgrounds of hereditary paraganglioma and pheochromocytoma (PPGL) are SDHx germline mutations. ![]()
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