Definitions

Atypical ductal hyperplasia
A benign (noncancerous) condition in which ductal cells are increased in number and look abnormal.
Biopsy
The removal of cells or tissue for examination by a pathologist. The pathologist may study the tissue under a microscope or perform other tests on the cells or tissue. When only a sample of tissue is removed, the procedure is called an incisional biopsy. When an entire lump or suspicious area is removed, the procedure is called an excisional biopsy. When a sample of tissue or fluid is removed with a needle, the procedure is called a needle biopsy, core biopsy, or fine-needle aspiration.
BI-RADS®
A method used by radiologists to interpret and report in a standardized manner the results of mammography, ultrasound, and MRI used in breast cancer screening and diagnosis. Also called Breast Imaging Reporting and Data System.
BRCA1
A gene on chromosome 17 that normally helps to suppress cell growth. A person who inherits certain mutations (changes) in the BRCA1 gene has a higher risk of getting breast, ovarian, prostate, and other types of cancer.
BRCA2
A gene on chromosome 13 that normally helps to suppress cell growth. A person who inherits certain mutations (changes) in the BRCA2 gene has a higher risk of getting breast, ovarian, prostate, and other types of cancer.
Breast density
Is determined by the relative amounts of fat, epithelial, and connective tissues that appear differently on a mammogram due to differences in X-ray attenuation. Fat appears radiolucent or dark, while epithelial and connective tissues are radiographically dense and appear light or white. A dense breast has less fat than glandular and connective tissue. Mammograms of breasts with high density are harder to read and interpret than those of less dense breasts.
Core biopsy
The removal of a tissue sample with a large diameter needle for examination under a microscope. Also called core needle biopsy.
DCIS (ductal carcinoma in situ)
A noninvasive condition in which abnormal cells are found in the lining of a breast duct. The abnormal cells have not spread outside the duct to other tissues in the breast. In some cases, ductal carcinoma in situ may become invasive cancer and spread to other tissues, although it is not known at this time how to predict which lesions will become invasive. Also called intraductal carcinoma.
Excisional biopsy
A surgical procedure in which an entire lump or suspicious area is removed for diagnosis. The tissue is then examined under a microscope.
Fine-needle aspiration biopsy
The removal of tissue or fluid with a thin needle for examination under a microscope. Also called FNA biopsy.
Invasive breast cancer
Cancer that has spread from where it started in the breast into surrounding, healthy tissue. Most invasive breast cancers start in the ducts (tubes that carry milk from the lobules to the nipple). Invasive breast cancer can spread to other parts of the body through the blood and lymph systems. Also called infiltrating breast cancer.
LCIS (lobular carcinoma in situ)
A noninvasive condition in which abnormal cells are found in the lobules of the breast. Having LCIS in one breast increases the risk of developing breast cancer in either breast.

Additional Reference
BRCA1 and BRCA2: Cancer Risk and Genetic Testing