Clinicopathological Features And Molecular Study Of Succinate Dehydrogenase-Deficient Renal Cell Carcinoma

Objective To investigate the protein expression and gene mutations of succinate dehydrogenase(SDH)subunits in succinate dehydrogenase-deficient renal cell carcinoma(SDH-deficient RCC),and to analyze the relationship between SDH-deficient RCC subunit gene mutations and protein expression and clinicopathological features.Methods Tissue microarray and immunohistochemistry(IHC)techniques were applied to detect the expression of SDH subunit proteins(including SDHA,SDHB,SDHC,SDHD,collectively called SDHx)in 900 cases of different histological types of renal tumors from2009 to 2023 at the Affiliated Hospital of Qingdao University and the Ninety-seventh Naval Hospital,and SDHx was applied to The whole exome sequencing was performed to detect SDHx and SDHAF1 and SDHAF2 gene mutations in 26 SDHx-negative cases and validated by Sanger sequencing;the tumor-associated 437 genes were detected in another6 SDHx-negative cases by applying second-generation sequencing technology.To summarize their clinicopathological features,molecular characteristics and prognosis.Results Among 900 renal tumors of different histological types,SDHx IHC was partially or completely negatively expressed in a total of 32 cases,and the diagnosis of SDH-deficient RCC was confirmed in 24 cases with mutations in the SDHx gene as verified by second-generation sequencing and Sanger sequencing.1.Clinical and prognosis: Among the 24 cases of SDH-deficient RCC,19 were male and5 were female,with age of onset ranging from 20 to 79 years,median age 49.5 years;12cases in the left kidney and 12 cases in the right kidney;one case had bilateral adrenal pheochromocytoma and a family history of pheochromocytoma;One case with neurofibromatosis 2(NF2)mutation had perirenal lymph node metastasis and survived postoperative immunotherapy,and two cases had postoperative pulmonary and hepatic metastases,respectively,with no recurrence or death at follow-up.2.Pathological features: grossly,the maximum diameter of tumor was 2.0-12.0 cm,with a median of 4.25 cm;microscopically: tumor cells were mostly arranged in solid sheets,glandular vesicles,papillae,and locally nest-like,tubular or small cyst-like arrangement,most tumor cells had translucent or acidophilic cytoplasm,transparent vacuoles and inclusion bodies were visible in the cytoplasm,and invaginated renal tubules were visible at the edge;p TNM stage,p T1 a stage 12 cases,p T1 b stage 9 cases,p T2 b stage 2 cases,p T4 stage 1 case.The p TNM stage,p T1 a stage 12 cases,p T1 b stage 9 cases,p T2 b stage 2cases,p T4 stage 1 case.3.IHC results: Among 24 cases of SDH-deficient RCC,16 cases(16/24)had negative SDHA expression;16 cases(16/24)had negative SDHB expression;9 cases(9/24)had negative SDHC expression;and 22 cases(22/24)had negative SDHD expression.4.Genetic test results: verified by second-generation sequencing and Sanger sequencing,SDHA gene mutations were detected in 6 cases(6/24),including 4 cases of SDHA gene missense mutations,1 case of SDHA gene shift mutation with NF2 gene shift mutation,and 1 case of SDHA gene splice site mutation,missense mutation with NF2 gene gaining stop codon mutation;Mutations in the SDHB gene were detected in 12 cases(12/24),including 3 cases of SDHB gene splice site mutations,1 case of SDHB gene gaining a stop codon mutation,1 case of SDHB gene missense mutation,7 cases of SDHB gene copy number variation(CNV);1 case of SDHC gene missense mutation(1/24);5 cases of SDHAF1 gene missense mutation(5/24).5.Relationship between gene test and IHC results: SDHx gene test results were consistent with the corresponding SDHx immunohistochemical expression results.SDHD protein immunohistochemistry was negative in all cases with SDHA gene mutation,and most of SDHB and SDHC were negative;SDHD was negative in all cases with SDHB gene mutation,and most of SDHA and SDHC were positive;SDHA and SDHD were negative in cases with SDHC gene mutation,and SDHB was positive;SDHA and SDHD were negative in most cases with SDHAF1 gene mutation,and most of SDHB and SDHC were positive.6.Relationship between gene results and histomorphology: SDHA gene mutation cases mainly showed papillary and solid lamellar arrangement,2 cases with NF2 gene mutation mainly showed papillary and glandular ductal arrangement with significant cell heterotypes,1 of which was accompanied by perirenal lymph node metastasis;SDHB gene mutation cases mostly showed solid lamellar and papillary arrangement;SDHC gene mutation 1 case showed solid lamellar arrangement;SDHAF1 gene mutation cases mainly showed glandular vesicular and papillary arrangement.Conclusion1.SDH-deficient type RCC occurs in young people and is more common in males,with an overall inert biological behavior and good prognosis.Metastasis may occur in a small number of cases.SDHA-deficient RCC and the accompanying NF2 gene mutation may increase tumor aggressiveness and metastasis.2.SDH-deficient RCC has obvious morphological diversity.In addition to the classic solid lamellar arrangement,vacuolated cells and low-grade nuclear features,papillary and adenoidal arrangements and high-grade nuclear features can be seen in SDH-deficient RCC,and cases with NF2 mutation mainly show papillary and adenoidal arrangements with significant cell heterogeneity.3.No significant correlation was detected between the protein expression of different subunits of SDHA,SDHB,SDHC,and SDHD,and mutations in any of the SDHx genes could lead to loss of SDHD protein expression,but not necessarily to loss of SDHB protein expression.4.There is inconsistency between the results of immunohistochemistry and genetic testing,and immunohistochemistry can be used as a screening method for SDH-deficient RCC,while genetic testing can help confirm the diagnosis of SDH-deficient RCC.5.The SDHA gene mutation rate in this study was higher than that reported in the literature and may be related to the ethnic population.6.Mutations in the SDHAF1 gene may cause deletion of SDHx subunit protein expression,leading to the development of SDH-deficient RCC.