Is calcium oxalate an adequate explanation for nonvisualization of breast specimen calcifications?

This study was initiated to determine whether the apparent calcium loss during histologic breast specimen processing could be explained by the presence of birefringent, transparent calcium oxalate crystals (type I). In previous investigations, the authors had noted a possible loss of 26.2% of calcium during the processing and sectioning of breast specimens. Two hundred thirteen histologic slides prepared from blocks demonstrating calcium radiographically but not histologically were reviewed with polarized light. An additional 506 slides from 19 malignancies appearing as microcalcifications were also reviewed with polarized light. Only one slide from each group (0.2% and 0.5% from the malignant and benign groups, respectively) demonstrated birefringent calcium oxalate (type I). Thus, the presence of calcium oxalate does not sufficiently explain the non-visualization of calcium, which is due instead to processing of breast specimens.