Reble, did you go to the vet yet? I found a thickening/lump on my dog's rump. Immediately took him to the vet. I cannot even report on what she did, or what she said beyond the words she hoped, in medical language, it was not a cancerous cyst. Whatever, whatever, whatever. Panic. Seriously, maybe it is nothing. But no one here knows. Denial is not your friend.