Even in the precancerous stage, called ductal carcinoma in situ (DCIS) when abnormal cells are confined to a milk duct, physicians almost always advise women to have a lumpectomy or mastectomy along with radiation, because about 20% of the 65, 000 cases of DCIS found every year in the U.S. become invasive cancer.

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In DCIS, abnormal cells multiply and form a growth within a breast milk duct .

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