Breast calcifications are common findings on mammography among women over the age of 50 years and about 1 in 10 mammograms of women under 50 years old. The malignant potential of a calcification is judged based on the morphology and distribution of calcifications within the breast. Microcalcifications refers to calcifications ranging from 0.1 millimeter (mm) to 1 mm. Previous findings showed that microcalcification clusters are more likely a sign of malignancy as compared to single microcalcifications (1,2). Improvements in mammography screening using high-resolution imaging techniques and magnification views allowed better detection of microcalcifications. Clinically, microcalcifications mammographic microcalcifications are known as one of the earliest signs of breast cancer, particularly so for the non-palpable breast cancers and are present in nearly one third of all breast cancers (3).

Several papers have published over the years on the association between microcalcifications and risk of breast cancer, however these studies have important limitations (4-8). They did not exclude microcalcifications without a malignant potential (mainly vascular calcifications), did not use an automated measure of calcifications, were underpowered and were mainly based on the case-controls and/or case report studies. In the current study, “Mammographic Microcalcifications and Risk of Breast Cancer”, we used the unique prospective Karolinska Mammography Project for Risk Prediction of Breast Cancer (KARMA) cohort, including 53,273 Swedish women to investigate the association between microcalcification clusters, and risk of overall and subtype specific breast cancer. We also examined if baseline mammographic density influenced the association between microcalcification clusters and risk of breast cancer using an FDA approved and non-reader dependent system (iCAD) for measure of mammographic density and microcalcifications.

In short, our results show that women with ≥3 microcalcification clusters had 2-folds higher risk of breast cancer compared to women with no clusters.  The risk was more pronounced among premenopausal women as compared to postmenopausal women. Among postmenopausal women, microcalcification clusters and mammographic density had a similar influence on breast cancer risk. No interaction was observed between microcalcification clusters and mammographic density. Finally, microcalcification clusters were significantly associated with in situ breast cancer.  

To conclude, our study is the first comprehensive attempt using a clinically proved method to detect suspicious microcalcification clusters and to shed light on the risk of breast cancer associated with the presence of microcalcification clusters separating for pre- and postmenopausal women. The biological mechanism by which calcium deposition occurs in the breast tissue is not clearly understood. It is therefore safe to state that more research is needed to identify the mechanisms behind mammographic microcalcifications formation and thereby the possible biological mechanism behind the association between microcalcifications and breast cancer.

We encourage readers to find more details in our full-text publication in British Journal of Cancer. Mammographic microcalcifications and risk of breast cancer

Illustration of suspicious microcalcification clusters using iCAD software on cranio-caudal views of a 74 years old woman with a lump in the right breast. iCAD software identified microcalcification clusters with suspicious morphology (iCAD Inc. Caption