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SDHD immunohistochemistry: a new tool to validate SDHx mutations in pheochromocytoma/paraganglioma.

The Journal of clinical endocrinology and metabolism (2014-11-19)
Mélanie Menara, Lindsey Oudijk, Cécile Badoual, Jérôme Bertherat, Charlotte Lepoutre-Lussey, Laurence Amar, Xavier Iturrioz, Mathilde Sibony, Frank Zinzindohoué, Ronald de Krijger, Anne-Paule Gimenez-Roqueplo, Judith Favier
ABSTRACT

Pheochromocytomas (PCC) and paragangliomas (PGL) may be caused by a germline mutation in 12 different predisposing genes. We previously reported that immunohistochemistry is a useful approach to detect patients harboring SDHx mutations. SDHA immunostaining is negative in SDHA-mutated tumors only, while SDHB immunostaining is negative in samples mutated on all SDHx genes. In some cases of SDHD or SDHC-mutated tumors, a weak diffuse SDHB labeling has however been described. Here, we addressed whether the same procedure could be applicable to detect patients with germline SDHD mutations, by testing two new commercially available anti-SDHD antibodies. We performed a retrospective study on 170 PGL/PCC in which we investigated SDHD and SDHB expression by immunohistochemistry. SDHx-mutated PGL/PCC showed a completely negative SDHB staining (23/27) or a weak cytoplasmic background (4/27). Unexpectedly, we observed that SDHD immunohistochemistry was positive in SDHx-deficient tumors and negative in the other samples. Twenty-six of 27 SDHx tumors (including the four weakly stained for SDHB) were positive for SDHD. Among non-SDHx tumors, 138/143 were positive for SDHB and negative for SDHD. Five cases showed a negative immunostaining for SDHB, but were negative for SDHD. Our results demonstrate that a positive SDHD immunostaining predicts the presence of an SDHx gene mutation. Because SDHB negative immunostaining is sometimes difficult to interpret in the case of background, the addition of SDHD positive immunohistochemistry will be a very useful tool to predict or validate SDHx gene variants in PGL/PCC.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Anti-SDHB antibody produced in rabbit, Prestige Antibodies® Powered by Atlas Antibodies, affinity isolated antibody, buffered aqueous glycerol solution
Sigma-Aldrich
Anti-SDHD antibody produced in rabbit, Prestige Antibodies® Powered by Atlas Antibodies, affinity isolated antibody, buffered aqueous glycerol solution