Depends how big it is. The biopsy will confirm it, or tell whether it is growing (malignant) or not (benign).

Mammograms are probably the most important tool doctors have not only to screen for breast cancer, but also to diagnose, evaluate, and follow people who’ve had breast cancer. Safe and reasonably accurate, a mammogram is an x-ray photograph of the breast. The technique has been in use for about 40 years. Screening mammograms are typically done every year to check the breasts for any early signs of breast cancer. Diagnostic mammograms are different from screening mammograms in that they focus on getting more information about a specific area (or areas) of concern — usually due to a suspicious screening mammogram or a suspicious lump. Diagnostic mammograms take more pictures than screening mammograms do. A mammography technician and a radiologist would coordinate to get the images your doctor needs to address that concern. The technician may need to magnify a suspicious area to produce a more detailed picture that will help your doctor make the diagnosis. 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 that it's not a cancer. Fibroadenomas are the most common kind of breast mass, especially in young women. “Before you go to get a mammogram, make sure you know whether you're there for a screening mammogram or a diagnostic mammogram. If you're there for your annual screening mammogram, you may not meet with the radiologist or get your results the same day. Sometimes, there's an advantage to this. Getting your results later often means having two doctors look at your mammogram. A lump, pain, nipple discharge, breast implants, or breast surgery automatically make your mammogram diagnostic. If you have a lump, or other symptoms, tell the mammography center so they know what they're dealing with. ”