For some reason not fully explained pigeons develop lumps om their bodies, it is an individual problem and is connected with the glands and the pigeons inability to cope with proteins, just like fatty lumps
They can be removed by tying a piece of thread round the base or left alone and they will fall off, pigeons seem to fully recover

they are nasty looking though info like this will help new starters coming on and maybe a few old heads will learn a thing