Glossary — D

DCIS stands for ductal carcinoma in situ, the earliest form of breast cancer. The abnormal cells are still contained within a milk duct and have not spread into surrounding breast tissue. Because it is caught so early, DCIS is highly treatable and often found through screening mammography before it can be felt.

Dense breast tissue means the breast has more glandular and fibrous tissue relative to fat. It is common, especially in younger women, and is identified on a mammogram, not by how the breast feels. Dense tissue appears white on a mammogram, the same color as many abnormalities, which can make them harder to spot.

A DEXA scan, short for dual-energy X-ray absorptiometry, is a quick, painless test that measures bone mineral density. Using a very low dose of X-rays, it helps your care team assess bone strength, diagnose osteoporosis or osteopenia, and estimate the risk of future fractures, often by scanning the hip and spine.

Doppler ultrasound is a special form of ultrasound that measures the movement of blood through vessels. By detecting how sound waves change as they bounce off moving blood cells, it can show the direction and speed of blood flow, helping detect narrowed or blocked vessels without any needles or radiation.

Ductal carcinoma is breast cancer that starts in the cells lining the milk ducts, the small channels that carry milk to the nipple. It is the most common type of breast cancer. When the cells remain inside the duct it is called in situ; when they grow beyond the duct wall it is called invasive.