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SUN-344 SDHB Immunostaining: Still an Indispensable Tool in Characterising Pheochromocytoma and Paraganglioma

ABSTRACT: Abstract Background: SDHB immunostaining can be used to functionally characterize SDH status in PCC and PGL. Assessing SDHB expression on tumors is inexpensive and can be used as an alternative to genetic testing. More importantly, assessment of SDHB expression can be of value in interpreting Variant of Unknown Significance (VUS) in SDH related genes. Objective: To investigate the effectiveness of SDHB immunostaining as an initial screening tool in identifying germline SDH mutations and the value of SDHB assessment in the clinical characterization of our patient cohort. Design: Prospective and retrospective analysis of 57 randomly selected patients with PCC and PGL from the year 1997 to 2018. Setting: In our institution on patients referred from London and South East England including Kent, Surrey and Sussex. Patients: Predominant Caucasian Population with diverse ethnicities. 57 patients - 34 patients (14M & 20F) with PGL and 25 with PCC (15M &10F). Age (mean: 41years at diagnosis with range 9-80 years). 2 patients had both PCC & PGL and multifocal PGLs were identified in few patients with SDHD and SDHB mutation. There were 65 tumors in total included in this study. Intervention: Resected tumor SDHB immunostaining with Sigma prestige antibodies (HPA002868 100UL - Anti-SDHB Rabbit monoclonal antibody) at a dilution of 1:1000. Genetic testing performed on predominant candidate genes. Main outcome measures: Concordance of SDHB loss of expression with presence of pathogenic mutation in candidate SDH genes. Secondarily, to explore SDHB immunostaining in our patient cohort with VUS in candidate genes. Results: SDHB immunostaining was negative in 22/23 tumors in patients with confirmed SDH mutation (false negative = 1 SDHB PCC where it was weak (+)). The staining was positive in 23/24 sporadic tumors, 10/11 VUS (in SDH, MAX and TMEM genes - both PCCs & PGLs), 2/2 PCCs in MEN-2, 2/2 PCCs in NF-1 and 2/3 PCCs in VHL. The negative immunostaining in 1 PGL with VUS in SDHB may imply lack of SDH enzyme activity and hence suggestive of a pathological mutation. The sensitivity is 96% and the specificity approaches 93% if the weak positive SDHB immunostaining with SDHD and VHL tumors were to be considered concordant. The concordance was 95% in the PGL group alone. Conclusions: SDHB immunostaining is a cost effective addition to PGL and PCC tumor characterization and performs with high sensitivity and specificity. SDH functional characterization has an important role in the management of patients who do not satisfy the current criteria for genetic testing (UK genetics testing directory for PCC/PGL). 18% of patients had VUS in a SDH related gene and we have found that SDHB immunostaining provided helpful information to inform follow-up and cascade screening decisions in this group.

SUBMITTER: Velusamy A

PROVIDER: S-EPMC6552923 | biostudies-literature | 2019 Apr

REPOSITORIES: biostudies-literature

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Project description:IntroductionPheochromocytomas and paragangliomas (PCC/PGL) are rare neuroendocrine tumors and can secrete catecholamine. Previous studies have found that SDHB immunohistochemistry (IHC) can predict SDHB germline gene mutation, and SDHB mutation is closely associated with tumor progression and metastasis. This study aimed to clarify the potential effect of SDHB IHC as a predictive marker for tumor progression in PCC/PGL patients.MethodsWe included PCC/PGL patients diagnosed in Ruijin Hospital, Shanghai Jiao Tong University School of Medicine from 2002 to 2014 for retrospective analysis and discovered that SDHB (-) staining patients had poorer prognoses. Then we examined SDHB protein expression by IHC on all tumors in the prospective series, which was composed of patients from 2015 to 2020 in our center.ResultsIn the retrospective series, the median follow-up was 167 months, and during follow-up, 14.4% (38/264) patients developed metastasis or recurrence, and 8.0% (22/274) patients died. Retrospective analysis revealed that 66.7% (6/9) of participants in the SDHB (-) group and 15.7% (40/255) of those in the SDHB (+) group developed progressive tumors (OR: 10.75, 95% CI: 2.72-52.60, P=0.001), and SDHB (-) was independently associated with poor outcomes after adjusting by other clinicopathological parameters (OR: 11.68, 95% CI: 2.58-64.45, P=0.002). SDHB (-) patients had shorter disease-free survival (DFS) and overall survival (OS) (P<0.001) and SDHB (-) was significantly associated with shorter median DFS (HR: 6.89, 95% CI: 2.41-19.70, P<0.001) in multivariate cox proportional hazard analysis. In the prospective series, the median follow-up was 28 months, 4.7% (10/213) patients developed metastasis or recurrence, and 0.5% (1/217) patient died. For the prospective analysis, 18.8% (3/16) of participants in the SDHB (-) group had progressive tumors compared with 3.6% (7/197) in the SDHB (+) group (RR: 5.28, 95% CI: 1.51-18.47, P=0.009), statistical significance remained (RR: 3.35, 95% CI: 1.20-9.38, P=0.021) after adjusting for other clinicopathological factors.ConclusionsOur findings demonstrated patients with SDHB (-) tumors had a higher possibility of poor outcomes, and SDHB IHC can be regarded as an independent biomarker of prognosis in PCC/PGL.

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SUN-344 SDHB Immunostaining: Still an Indispensable Tool in Characterising Pheochromocytoma and Paraganglioma

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