Most screening mammograms include two views of each breast taken from different angles. Diagnostic mammograms involve taking more views than screening mammograms. Even if you have a lump in only one breast, pictures will be taken of both breasts. This is so the breasts can be compared and so that the other breast can be checked for abnormalities. If you’ve had a mammogram before, the radiologist should compare your old mammogram to the new one to look for changes.
While they’re looking for possible cancer, your doctors may also come across masses or structures in the breast that deserve further investigation, including:
Calcifications: Calcifications are tiny flecks of calcium — like grains of salt — in the soft tissue of the breast that can sometimes indicate the presence of an early breast cancer. Calcifications usually can’t be felt, but they appear on a mammogram. Depending on how they’re clustered and their shape, size and number, your doctor may want to do further tests.
Big calcifications — "macrocalcifications" — are usually not associated with cancer. Groups of small calcifications huddled together, called "clusters of microcalcifications" are associated with extra breast cell activity. Most of the time this is non-cancerous extra cell growth, but sometimes clusters of microcalcifications can occur in areas of early cancer.
Cysts: Unlike cancerous tumors, which are solid, cysts are fluid-filled masses in the breast. Cysts are very common and are rarely associated with cancer. A follow-up ultrasound is the best way to tell a cyst from a cancer, because sound waves pass right through a liquid-filled cyst. Solid lumps, on the other hand, bounce the waves right back to the film.
Fibroadenomas: Fibroadenomas are movable, solid, rounded lumps made up of normal breast cells. While not cancerous, these lumps may grow. And any solid lump that’s getting bigger is usually removed to make sure it’s not a cancer. Fibroadenomas are the most common kind of breast mass, especially in young women. ... Source: breastcancer.org.