I discovered a lump on my 13-week-old chicken yesterday. It is the size of a quarter or so and flattish (not round like a grape tomato, but more like a ... small cookie in shape?). It is firmish but soft. I see no outward wound, scab, blood, etc. When pushing feathers aside, I see just a yellow lump. It is centered and low on her chest. I have other birds that if you feel their chest you can feel what I'm assuming to be the top of the keel. This seems to be at the top of the keel where the end of the bone is. When she roosts it seems to be on the part of her chest that sits on the roost, essentially between her feet. From my googling, the closest thing I could come up with was a breast blister. However, they seem to happen primarily in meat birds and relate with leg issues or laying on the floor a lot. She is acting normally and eating, roosting, etc. I wouldn't have known it was there if I didn't pick her up. She is squirmy, but I've felt it while she is roosting and tried to grab a few photos tonight. Is this a breast blister? If so, it sounds like I need a vet to lance it? It does not look like something that is anywhere close to opening up on its own. My first thought is to keep an eye on it for a few days and check with a vet, but I thought I'd see what other people think. I'm new to chickens (clearly). Also, to be clear: it is definitely not her crop. I already had the tumor/crop freak out several weeks ago. This is lower than her crop. With and without red circle showing where it is (circle not necessarily to scale) Underneath. Hard to see the full size here.