Relationships between pathology and crystal structure in breast calcifications: an in situ X-ray diffraction study in histological sections

Abstract

Calcifications are not only one of the most important early diagnostic markers of breast cancer, but are also increasingly believed to aggravate the proliferation of cancer cells and invasion of surrounding tissue. Moreover, this influence appears to vary with calcification composition. Despite this, remarkably little is known about the composition and crystal structure of the most common type of breast calcifications, and how this differs between benign and malignant lesions. We sought to determine how the phase composition and crystallographic parameters within calcifications varies with pathology, using synchrotron X-ray diffraction. This is the first time crystallite size and lattice parameters have been measured in breast calcifications, and we found that these both parallel closely the changes in these parameters with age observed in fetal bone. We also discovered that these calcifications contain a small proportion of magnesium whitlockite, and that this proportion increases from benign to in situ to invasive cancer. When combined with other recent evidence on the effect of magnesium on hydroxyapatite precipitation, this suggests a mechanism explaining observations that carbonate levels within breast calcifications are lower in malignant specimens.

Figure 1

All-specimens sum diffractogram and digitally isolated large crystallite diffractogram versus theoretical line positions and intensities.

Figure 2

Whitlockite weight percentage average per specimen, grouped by diagnosis. Malignant specimens contain significantly more whitlockite than those with a benign diagnosis. Individual specimen details are available in Supplementary Information.

Figure 3

Hydroxyapatite crystalline domain dimensions, averaged by specimen and categorized by diagnosis. Malignant specimens have significantly larger crystalline domain size in both axes than benign specimens.

Figure 4

Hydroxyapatite lattice parameters, averaged by specimen and categorized by diagnosis. There is a significant negative correlation between ‘a’ and ‘c’ lattice parameters, and the ‘c’ lattice parameter is significantly smaller in benign than in malignant specimens.

Figure 5

H&E stained images of typical calcifications: (a) Specimen X44 (B2), (b) Specimen X53 (B5a), (c) Specimen X46 (B5b). Histopathology summaries can be found in Supplementary Table S1.