Candi, I understand your fear; breast lumps are just plain scary! However, an ultrasound is the usual method for determining if a lump is a cyst; and it's very reliable. The techs should be able to tell, by looking, that what you're feeling is a cyst, not a tumor. In addition, irregular periods and pain aren't breast cancer symptoms. However, since you're obviously quite uncomfortable, why not ask the doctor to drain the cyst? That way you'd prove to yourself that it IS a cyst (since tumors can't be drained). And if by some chance it's not a cyst, the doctor would find that out, too. Sound like a plan? In the meantime, please don't stress; totally doesn't sound like breast cancer... Good luck -PJH