Potential Pitfalls of SDH Immunohistochemical Detection in Paragangliomas and Phaeochromocytomas Harbouring GermlineSDHxGene Mutation.
Germline mutations in any of the succinate dehydrogenase (SDH) genes result in destabilization of the SDH protein complex and loss of SDHB expression at immunohistochemistry. SDHA is lost together with SDHB in SDHA-mutated tumours, but its expression is retained in tumours with other SDH mutations. We investigated whether SDHA/SDHB immunohistochemistry is able to identify SDH-related tumours in a retrospective case series of phaeochromocytomas (PCCs) and paragangliomas (PGLs).



SDHA and SDHB immunostaining was performed in 13 SDH gene-mutated tumours (SDHB: n=3; SDHC: n=1; SDHD: n=9) and 16 wild-type tumours. Protein expression by western blot analysis and enzymatic activity were also assessed.



Tumours harbouring SDH gene mutations demonstrated a significant reduction in enzymatic activity and protein expression when compared to wild-type tumours. SDHB immunostaining detected 76.9% of SDH mutated PCCs/PGLs (3/3 SDHB-mutated samples; 1/1 SDHC-mutated sample; 6/9 SDHD-mutated samples). In three SDHD-related tumours with the same mutation (p.Pro81Leu), positive (n=2) or weakly diffuse (n=1) SDHB staining was observed. All wild-type PCCs/PGLs exhibited SDHB immunoreactivity, while immunostaining for SDHA was positive in 93.8% cases and weakly diffuse in one (6.2%). SDHA protein expression was preserved in all tumours with mutations.



SDHA and SDHB immunohistochemistry should be interpreted with caution, due to possible false-positive or false-negative results, and ideally in the setting of quality assurance provided by molecular testing. In SDHD mutation, weak non-specific cytoplasmic staining occurs commonly, and this pattern of staining can be difficult to interpret with certainty.
Division of Pathological Anatomy, University of Florence, Florence, Italy.
Raffaella
R
Santi
Department of Clinical Pathophysiology, University of Florence, Florence, Italy.
Elena
E
Rapizzi
Department of Clinical Pathophysiology, University of Florence, Florence, Italy.
Letizia
L
Canu
Department of Clinical Pathophysiology, University of Florence, Florence, Italy.
Tonino
T
Ercolino
Division of Pathological Anatomy, University of Florence, Florence, Italy.
Gianna
G
Baroni
Department of Clinical Pathophysiology, University of Florence, Florence, Italy.
Rossella
R
Fucci
Department of Clinical Pathophysiology, University of Florence, Florence, Italy.
Giuseppe
G
Costa
Department of Clinical Pathophysiology, University of Florence, Florence, Italy.
Massimo
M
Mannelli
Division of Pathological Anatomy, University of Florence, Florence, Italy gabriella.nesi@unifi.it.
Gabriella
G
Nesi
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015153:Blotting, Western; D042963:Electron Transport Complex II / Q000096:biosynthesis* / Q000235:genetics; D005260:Female; D018095:Germ-Line Mutation; D006801:Humans; D007150:Immunohistochemistry / Q000379:methods*; D008297:Male; D008565:Membrane Proteins / Q000096:biosynthesis / Q000235:genetics; D008875:Middle Aged; D010235:Paraganglioma / Q000175:diagnosis / Q000201:enzymology* / Q000235:genetics; D010673:Pheochromocytoma / Q000175:diagnosis / Q000201:enzymology* / Q000235:genetics; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D013385:Succinate Dehydrogenase / Q000096:biosynthesis* / Q000235:genetics; D055815:Young Adult
D008565:Membrane Proteins; C108096:SDHC protein, human; C491545:SDHD protein, human; D042963:Electron Transport Complex II; C511268:SDHA protein, human; C108095:SDHB protein, human; D013385:Succinate Dehydrogenase
Phaeochromocytoma; SDHB; SHDA; immunohistochemistry; paraganglioma; succinate dehydrogenase