Appearance Fawn English Mastiff With a massive body, broad skull and head of generally square appearance, it is the largest dog breed in terms of mass. It is on average slightly heavier than the Saint Bernard, although there is a considerable mass overlap between these two breeds. 11 mai 2021 · By Denise Flaim Published: May 11, 2021 | 4 Minutes Updated: May 19, 2021 Mastiff circa 1921 AKC History working group mastiff “What the Lion is to the Cat,” wrote Sydenham Edwards in 1800,.