I agree! Tosa would be my first, second and third guess....my fourth would be a Boerboel assuming that it was a purebred....if it is a mix then there are a lot of possibilities.
He has a lot of bullmastiff qualities, but lacks pigment which would be present in most mastiff or bullmastiff mixes. I would say maybe even some Fila in there possibly which could explain the pigment...
WOW, that dog is GORGEOUS and STRIKING. I would take him in a heart beat if I could!!
First thing I though was boerboel. But I think its more of a bull mastiff mix of some kind since they are more common. I would be very surprised if he wasnt part bull mastiff. I think he is too built for a tosa, but who knows! Maybe even some presa blood in there. He could be many things.
I see Tosa, but could also be French Mastiff/BullMastiff mix or soemthing like that. TOsa was my first thought though, there was a neo in the shelter here recently.
You know what we had in a shelter that was really random? A Mexican Hairless. No mistaking it for anything else.
///off topic///
So I'd say a rare breed could happen, but I still think there's something bullmastiff like about him. I still bet bullmastiff x something with a more moderate head structure. Plus it's more probable.
We had a young female Neapolitan Mastiff at FOHA two years ago. Nobody had taught her that it was not appropriate to jump on/mouth humans 0_0. She was adopted and returned three times for being too much dog to handle. The third time she came back she was cowering in her run, and when she'd left she'd been a very outgoing, confident dog . But the fourth time was the charm.
This is her (this pic is dark, she was more silvery in person):
Neos are one of those breeds that when they cross with another dog...the puppies always turn out to be great looking dogs. I am not a fan of Neos (looks wise) as purebreds, but they make great mixed breeds
Not much chance that would do any good, since those use breeds recognized by the AKC and very few, if any non-recognized breeds, from what I've been told.