Hi! I know from my own personal experience, that a lump I felt and marked with a sharpie was not showing up as anything significant on a mammogram or the ultrasound .  I was told it was because I had lumpy breast tissue and what I was likely feeling was a cyst that would eventually go away.  The tech ended up being right, but my fears continued constantly for another 2 years at which time I chose to have a mastectomy preformed (I already had one done on the other side due to cancer.) Like PJ suggests, find a doctor who specializes in breast health and seek out their opinion.  Get the needle biopsy done if need be, but their are also other diagnostic tools that your doctor can use to help determine what exactly it is.  Till then track the changes, if any. Best of luck to you. Angi