A 26-year-old woman has a lump in her left breast

A 26-year-old woman has a lump in her left breast.

On physical examination, she has an irregular, firm, 2-cm mass in the upper inner quadrant of the breast. No axillary adenopa thy is noted. A fine-needle aspirate of the mass shows anaplas tic ductal cells.

The patient’s 30-year-old sister was recently diagnosed with ovarian cancer, and 3 years ago her maternal aunt was diagnosed with ductal carcinoma of the breast and had a mastectomy.

BRCA1 (DNA repair gene)