A week or so ago we noticed what we thought was fat around the back of Charlie's neck, didn't think much of it at first since he's a puppy. However, now it hasn't gone away and is becoming more concentrated to the side of the neck towards his shoulder blade. We were feeling around this morning and found a smaller slightly hard lump inside the larger area and it seems to hurt him because he doesn't like it being messed with. Vets closed on Sunday's so we can't take him until tomorrow. Does anybody know what this might be, I'm very worried about him. Here's a photo. You can see the "fat mass" on the left side of his neck/shoulder area.