A somatic missense mutation in exon 4 (c.365A>G) of the SDHD gene, causing a p.Lys122Arg substitution in the protein, was identified in canine PGLs [24,25] screening exons 2, 3, and 4 of the SDHD gene in canine paragangliomas (PGL) and pheochromocytomas (PC) is crucial due to potential role in tumorigenesis. This evidence concerns the gene SDHD and pheochromocytoma.