Microcalcifications in breast cancer: an active phenomenon mediated by epithelial cells with mesenchymal characteristics

Abstract

BackgroundMammary microcalcifications have a crucial role in breast cancer detection, but the processes that induce their formation are unknown. Moreover, recent studies have described the occurrence of the epithelial–mesenchymal transition (EMT) in breast cancer, but its role is not defined. In this study, we hypothesized that epithelial cells acquire mesenchymal characteristics and become capable of producing breast microcalcifications.MethodsBreast sample biopsies with microcalcifications underwent energy dispersive X-ray microanalysis to better define the elemental composition of the microcalcifications. Breast sample biopsies without microcalcifications were used as controls. The ultrastructural phenotype of breast cells near to calcium deposits was also investigated to verify EMT in relation to breast microcalcifications. The mesenchymal phenotype and tissue mineralization were studied by immunostaining for vimentin, BMP-2, β2-microglobulin, β-catenin and osteopontin (OPN).ResultsThe complex formation of calcium hydroxyapatite was strictly associated with malignant lesions whereas calcium-oxalate is mainly reported in benign lesions. Notably, for the first time, we observed the presence of magnesium-substituted hydroxyapatite, which was frequently noted in breast cancer but never found in benign lesions. Morphological studies demonstrated that epithelial cells with mesenchymal characteristics were significantly increased in infiltrating carcinomas with microcalcifications and in cells with ultrastructural features typical of osteoblasts close to microcalcifications. These data were strengthened by the rate of cells expressing molecules typically involved during physiological mineralization (i.e. BMP-2, OPN) that discriminated infiltrating carcinomas with microcalcifications from those without microcalcifications.ConclusionsWe found significant differences in the elemental composition of calcifications between benign and malignant lesions. Observations of cell phenotype led us to hypothesize that under specific stimuli, mammary cells, which despite retaining a minimal epithelial phenotype (confirmed by cytokeratin expression), may acquire some mesenchymal characteristics transforming themselves into cells with an osteoblast-like phenotype, and are able to contribute to the production of breast microcalcifications.

Energy Dispersive X-ray (EDX) Microanalysis in Biomedical Research

“…In these fields, we applied EDX microanalysis to demonstrate a different elemental composition of calcifications associated to benign or malignant breast lesions. Notably, we detected for the first time magnesium-substituted hydroxyapatite, never found before, in benign lesions but frequently present in breast cancer [5] . In the last years, the study of asbestos became very interesting and the characterization of the asbestos fibers was better defined thank to EDX microanalysis.…”

“…The EDX microanalysis was also used to add more information about the link between calcium deposition and human diseases [5,6] . In these fields, we applied EDX microanalysis to demonstrate a different elemental composition of calcifications associated to benign or malignant breast lesions.…”

“…In a recent paper, we demonstrated existence of important differences between lung cancer lesions and benign lesions about bioaccumulation of heavy metals, such as Co, Cr and Pb. The identification of toxic elements involved in lung carcinogenesis can provide additional evidence on strictly association between cancer and environmental pollution [1] .The EDX microanalysis was also used to add more information about the link between calcium deposition and human diseases [5,6] . In these fields, we applied EDX microanalysis to demonstrate a different elemental composition of calcifications associated to benign or malignant breast lesions.…”

Microcalcification on mammography: approaches to interpretation and biopsy

“…3 Magnesium-substituted hydroxyapatite has also been reported. 4 There is evidence that a change in levels and calcium carbonate content of hydroxyapatite may influence breast cancer cell growth. 5 Radiographic microcalcification was first described in 1913 by Albert Salomon, a surgeon in Berlin.…”

Importance of microcalcifications in mammographic differentiation of the invasive ductal breast cancer and of the ductal carcinoma in situ

“…Around 50% of non-palpable breast cancers are detectable on mammograms, based only on microcalcifications, as around 90% of ductal carcinomas in situ are detected due to calcifications (9). DCIS is a complex clinical entity that is highly variable in its appearance, biology, and behavior (10).…”