When you hold the bird and feel for the "lump" is it between the tail and the vent or between the vent and breast bone? Roosters will often have a lump between their tail and vent, this is their foam gland and if you press it gently but firmly a good amount of foam will come out, maybe the volume of a peanut. This area will usually be a redder color than the rest of the roosters' skin. In hens this area is paler in color, more like the rest of their skin.