Hereditary succinate dehydrogenase-deficient renal cell carcinoma

Succinate dehydrogenase (SDH), formed by four subunits SDHA, SDHB, SDHC, SDHD, and an assembly factor SDHAF2, functions as a key respiratory enzyme. Biallelic inactivation of genes encoding any of the components, almost always in the presence of a germline mutation, causes loss of function of the entire enzyme complex (socalled SDH deficiency) and subsequent development of SDH-deficient neoplasms which include pheochromocytoma/paraganglioma, gastrointestinal stromal tumor, and renal cell carcinoma (RCC). These tumors may occur in the same patient or kindred. SDH-deficient RCC shows distinctive morphological features with vacuolated eosinophilic cytoplasm due to distinctive cytoplasmatic inclusions containing flocculent material. The diagnosis is confirmed by loss of SDHB on immunohistochemistry with positive internal control. The majority of tumors occur in the setting of germline mutations in one of the SDH genes, most commonly SDHB. The prognosis is excellent for low-grade tumors but worse for high-grade tumors with high-grade nuclei, sarcomatoid change, or coagulative necrosis. Awareness of the morphological features and low-threshold for applying SDHB immunohistochemistry help identify patients with SDH-deficient RCC and hereditary SDH-deficient tumor syndromes. In this review we summarize recent development on the clinical and genetic features, diagnostic approach, and pitfalls of SDH-deficient syndrome, focusing on SDH-deficient renal cell carcinomas.