Swell at neck of Rottweiler

What will cause a swell at neck area of a Female Rottweiler?

[ginger899]

OK, lots of questions....
Has she recently been in a fight, or been playing too hard with another dog, and could maybe have got a small puncture wound?
Is the swelling at the side of her neck under her jaw, or at the sides?
Does she seem lethargic (doesn't want to go for walks, wants to lay on her bed or sleep more?)
Does she seem to be in pain?
Is she eating OK? Does she seem to eat slower than before, or having any difficulty chewing her food?
Is the swelling like a kind of lump? If so, is it a lump that when you push it with your fingers it feels soft and moves about quite freely, or does it seem like a solid mass? -Or is the swelling bigger than that and more widespread?