Succinate Dehydrogenase-Deficient Renal Cancer Featuring Fructose-1,6-Biphosphatase Loss, Pyruvate Kinase M2 Overexpression, and SWI/SNF Chromatin Remodeling Complex Aberrations: A Rare Case Report.

Succinate dehydrogenase (SDH)-deficient renal cancer is a rare renal cancer subtype recently accepted by the World Health Organization as a unique subtype of renal cell carcinoma (RCC). Here we report a case of 17-year-old man. The detailed evaluation indicated occurrence of the SDHB-deficient RCC. The genetic testing revealed no germline mutation in SDH genes. Immunohistochemistry showed SDHB deficiency, overexpression of pyruvate kinase M2 and dramatic downregulation of fructose-1,6-bisphosphatase metabolic enzymes, and unaltered levels of phosphorylated AMP-activated protein kinase and mammalian target of rapamycin. Strong upregulation of INI1 and BRG1 and overexpression of BAF180, subunits of SWI/SNF ATP-dependent chromatin remodeling complex, were also found. The identified tumor pathologically did not resemble clear cell renal cell carcinoma (ccRCC), but some metabolic alterations are common for both cancer types. Thus, we postulate that the phenotypical differences between ccRCC and SDHB-deficient RCC may be related to distinct molecular and metabolic alterations. IMPLICATIONS FOR PRACTICE: Succinate dehydrogenase (SDH)-deficient renal cell carcinoma (RCC) is a rare renal tumor occurring even in young patients. Until now, in all described and genetically tested cases, mutations and deletions in SDH genes have been found. This article describes SDHB-deficient RCC without any germline mutations in SDH genes. Therefore, genetic analysis for germline mutations in SDH genes in SDH-deficient RCC, especially in young individuals, should be strongly recommended, although as of now it is not obligatory. This knowledge will allow improvement of patient monitoring including both disease recurrence and new cancer appearance.