http://www.liherald.com/stories/Small-dog-attacked-by-local-Mastiff-in-Lynbrook,39979?page=1&content_source=
The "American Mastiff" is a designer breed recognized by the Continental Kennel  Club and has only been in existence less than 25 years. It was created by  crossing the English Mastiff with a livestock guard dog breed --Anatolian  Shepherd. This breed's founder stated her purpose was to  eliminate genetic health problems, increase the life expectancy, and to produce  a "dry Mouth" mastiff. Also often advertised as an "improved" Mastiff and  marketed as a potential "new Breed", it is in fact a cross-bred--7/8 Mastiff and  1/8 Anatolian Shepherd. Many an owner of an "American Mastiff" will inform you  it is the SAME dog as an "English Mastiff" only born here in "America"--thus  it's an "American Mastiff". I hate to be the messenger of bad news-- but that  ain't so, folks
Many AmMa owners  discover marked aggressive traits in their young dogs at 8-24 months ; a period  of canine development when all dogs go through a fear and dominance stage.  Because of the influence of the Anatolian Shepherd which is a Guarding breed--  an inborn "guarding instinct" begins to develop and these dogs can become very  aggressive toward strangers and if they have not been socialized and obedience  trained, very difficult to train and control. These dogs can become too  aggressive for the average owner to keep and they find their once loving  manageable puppy has now become an uncontrollable dominate dog. It takes a very  experienced "dog savey" person to handle a dog with aggression  and dominance issues. Most dog owners are poorly prepared to deal with these  problems in any dog much less a giant breed.
(http://kiokeemastiffscom.blogspot.com/2008/01/american-mastiff-is-not-mastiff.html)