UPDATE:
The vet saw her. It was a feather cyst. He removed it pretty quickly. Because of its size, it was about to rupture the skin anyway. That's why it looked so bruised. No infection, just the feather and fat.
He punctured the cyst with a pair of scissors, and then, as he opened the...
They're pets for me so I handle them a lot. But also purposely examine them once a week or so. I've spotted injuries, small prolapses, flystrike, etc. this way.
However, this huge ingrown feather is pretty obvious because it is on a bald patch this chicken has (she's been molting forever).
I...
There's an avian vet who comes to my town every Tuesday. I will ask him about this next Tuesday and I will let you know what he says.
The chicken actually has three more of these lumps: two small, skin-colored ones, and one that has been "ruptured" by the feather (the feather came out from...