Positive Immunostaining for Succinate Dehydrogenase B (SDHB) in Paraganglioma Associated with Germline Mutation of SDHB, L157X and P236S.

PURPOSE: Pheochromocytoma (PCC) and paraganglioma (PGL) associated with the succinate dehydrogenase (SDH) germline mutations are characterized by negative results of immunohistochemistry tests for SDH subunit B (SDHB). Genetic testing for the SDH complex (SDHA, SDHB, SDHC, SDHD, and SDHAF2) is indicated only in patients with those diseases in whom immunohistochemistry tests for SDHB as a surrogate marker to detect the SDH complex mutation yield negative results. Two novel SDHB germline mutations, L157X and P236S, in PGL were previously reported. We therefore examined immunohistochemistry testing for SDHB in the PGLs with the SDHB germline mutations of L157X and P236S. METHODS: Immunohistochemistry for SDHB was performed in PGLs with the SDHB germline mutations of L157X and P236S. Five cases of sporadic PCC were subject to immunohistochemistry testing for SDHB. Normal tissue from the adrenal cortex adjacent to the sporadic PCC was used as the external positive control. RESULTS: Immunohistochemistry results were positive for SDHB in PGLs with the SDHB germline mutation of L157X and P236S, all five cases of sporadic PCC, and the adrenal cortex as the external positive control. CONCLUSION: Immunohistochemistry tests for SDHB showed positivity in PGLs associated with the SDHB germline mutations of L157X and P236S. Thus, immunohistochemistry testing for SDHB might not always reveal a surrogate marker in formal genetic testing of the SDH complex.