Breast calcifications are small deposits of calcium salts that appear as bright white specks on a mammogram. These deposits are common, particularly in women over 50, and are unrelated to dietary calcium or supplements. Calcifications are usually too small to be felt, making the mammogram the primary detection method. While the presence of these specks is not an automatic diagnosis of cancer, their appearance helps radiologists determine if further evaluation is necessary.
The Biology of Breast Calcifications
The formation of breast calcifications is a physiological process known as dystrophic calcification. This occurs when calcium salts precipitate in tissue that is damaged, degenerating, or otherwise abnormal. The calcium is deposited as the body attempts to repair or wall off areas of cellular debris or inflammation.
Common benign processes can lead to this deposition, such as normal aging, which results in calcium accumulating in the blood vessels of the breast. Calcifications are also associated with benign growths like fibroadenomas, breast cysts, and mammary duct ectasia (inflammation of the milk ducts). Past trauma, previous infections, or prior radiation therapy can also cause calcifications to form in resulting scar tissue.
When calcifications are associated with malignancy, they typically form when abnormal cells grow unchecked inside a milk duct. As these cells multiply rapidly, some die and are unable to be cleared away by the body. The resulting cellular debris hardens, leading to the formation of calcium deposits within the ducts themselves.
Categorizing Calcifications by Appearance
Radiologists classify calcifications based on their size, shape, and pattern on the mammogram to assess the probability of them being benign or malignant. The two main size categories are macrocalcifications and microcalcifications. Macrocalcifications are larger, coarse deposits, typically measuring greater than 0.5 millimeters, and appear as large, distinct white dots or dashes.
These larger calcifications are almost always noncancerous and usually do not require follow-up or testing. They often represent long-standing, benign conditions like an involuting fibroadenoma or fat necrosis (the breakdown of fatty tissue after an injury). Their well-defined appearance is a strong indicator of a benign process.
Microcalcifications are tiny specks of calcium, measuring less than 0.5 millimeters, and are the type that requires greater scrutiny. Although usually benign, they are the finding most commonly associated with early-stage breast cancer, particularly ductal carcinoma in situ (DCIS). The pattern in which these microcalcifications are distributed is a crucial factor in their classification.
Suspicious patterns include “pleomorphic” calcifications, which have various shapes and sizes, or those arranged in a tight “cluster” of at least five specks. A “linear” or “branching” pattern, suggesting deposits forming along a milk duct, is also highly suspicious. Calcifications that are “diffuse” or scattered randomly throughout the breast are typically benign, while those in a “segmental” pattern warrant further investigation.
Assessing Risk and Diagnostic Follow-Up
Radiologists use the visual appearance and distribution of the calcifications to assign an assessment code from the Breast Imaging Reporting and Data System (BI-RADS). This standardized system helps communicate the level of suspicion and the recommended follow-up action.
Most calcifications fall into BI-RADS Category 2, meaning the finding is definitively benign, such as a cluster of round, uniform calcifications, and the woman should return for routine annual screening.
BI-RADS Category 3 findings are considered “probably benign,” with a less than 2% chance of being cancer. These findings typically lead to a recommendation for a short-interval follow-up mammogram, usually in six months, to ensure they remain stable over time. If the calcifications show no change after a year, the woman can usually revert to annual screening.
A finding placed in BI-RADS Category 4 is “suspicious for malignancy” and has a 2% to 95% probability of being cancerous, necessitating a biopsy. This category is subdivided into 4A (low suspicion), 4B (moderate suspicion), and 4C (high suspicion) to reflect the increasing level of concern based on the morphology and pattern. Category 5 is reserved for findings that are “highly suggestive of malignancy,” carrying a greater than 95% risk of cancer, and always requires a biopsy.
The definitive diagnostic tool for suspicious microcalcifications is a stereotactic core needle biopsy, an outpatient procedure guided by mammography. The patient lies on a specialized table, and the breast is compressed while X-ray images pinpoint the exact location of the calcifications. After a local anesthetic is applied, a vacuum-assisted device extracts multiple small tissue samples containing the calcifications. A small metal clip is often placed at the biopsy site to mark the location for future reference. The tissue samples are then sent to a pathologist for microscopic examination, which provides a final diagnosis to guide any necessary treatment.