A breast hamartoma is a benign lesion diagnosed on a core biopsy. It may be felt as a lump or detected on a mammogram or an ultrasound incidentally without being felt.
A hamartoma is made of various amounts of fat, breast glands and fibrous tissue (just like the normal breast). It is like another small breast inside your breast.
Although a core biopsy can suggest that a lesion is a hamartoma, it is difficult to get a definitive diagnosis without removing the whole lesion. A concurrent malignancy can co-exist and therefore excision is recommended.