Calcium formations within the breast are common in all women but more common in postmenopausal women. According to the Mayo Clinic, most calcifications turn out to be harmless, but they can indicate harmful cysts, infection (mastitis) or cancer. Small white dots on a mammogram are called microcalcifications. Larger white spots or lines are called macrocaclifications. Radiologists evaluate clusters of calcium deposits for both their distribution patterns and the shapes of the calcifications.

Diffuse or Scattered Clusters

In a 2008 article in "The Radiology Assistant," Dutch radiologists Robin Smithuis and Ruud Pinappel note that calcium formations that are dispersed or scattered throughout or within a region of the breast indicate lobular calcifications because most of the breast is involved in the process that forms these deposits. Lobular calcifications form in the milk-producing lobules and most often are benign.

Regional or Segmental Clusters

Clusters scattered among several regions of the breast also usually indicate benign formations. Patterns of white spots on the mammogram that appear in clusters within a single region or segment of a lobe are more problematic for the radiologist to evaluate and are classified as of intermediate concern.

Linear Clusters

A single compact cluster of spots or a pattern that appears in a line within a small area of the breast can indicate a type of cancer called ductal carcinoma in situ, or DCIS.

Popcorn Clusters

The most important factor in determining whether a calcification cluster is benign or malignant is the form the calcium takes, according to radiologists Smithuis and Pinappel. If the spots show as rounded, pointy or popcorn-like structures they most often are benign.

Cloud-like Clusters

If the calcification clusters are formless, or cloud-like, they are considered suspicious or of intermediate concern and may require further tests.

Branching Clusters

Formations that appear in lines or branching lines indicate deposits in the milk ducts or blood vessels. Linear spots in a blood vessel indicate coronary artery disease. A linear formation in the milk ducts is suggestive of DCIS, which represents 25 to 30 percent of all breast cancers. With these linear formations, your doctor will need to do a biopsy to conclusively determine whether it is cancer.