What breed is my dog
 

:confused: Can anyone tell me what breed is my dog

?
 

Looks to me like a West Highland White Terrier, but this dog should look more bold, almost daring with a varminty appearance. His ears are not of correct shape and not erect; not in full coat. Head should be covered with hair with skull slightly domed.

Is this dog a pure breed?

Without a side view it's hard to tell. It's definitely a cross breed but unlikely a Westie. Probably a Maltese X Shih Tzu or Maltese X Spaniel.

The owner say is was mixed terrier

Yes, I think you`re right: this dog certainly has a West Highland TERRIER face (only not a good specimen of the breed) who is probably crossed with another terrier/toy dog white breed e.g. Maltese, another cross spaniel cross. As I mentioned, his ears are incorrectly shaped, eyes are too large, coat texture seems incorrect too. Cross breeds are naturally hard to ascertain as more than 2 breeds could have crossed !

Is the dog healthy? (this is more important!)

Regarding your dog's breed...
 

I covered the head with my hand and it does resemble a toy poodle with the fur... how does the fur grow like... and does it keep growing? (Sorry! This is my opinion, and I'm not a professional, just that I'd had a poodle before) Your dog's very adorable even if its mixed. Unique :)

Ya no matter what breed it is, is still our love dog. :) :)