High-Grade Histologic Features of DCIS are Associated with R5 Rather than R3 Calcifications in Breast Screening Mammography

Abstract

Mammographic calcification is an important radiologic feature of early breast carcinoma whose index of suspicion for malignancy may be reported by a five-tier R-category system. This study aims to describe the histologic diagnoses underlying screen-detected mammographic calcifications using both digital and screen-film mammography, and to correlate these findings with radiologic R-categories. Patients attending the Merrion Breast Screening Unit in Dublin between 2000 and 2011 were identified, who underwent needle-core biopsy for assessment of mammographic calcifications without associated mass or architectural distortion. Radiologic R-category was correlated with biopsy and excision histology reports. A total of 776 cases of calcification were identified, involving 769 individual patients. The radiologic R-categories were as follows: R3 513 (66.1%), R4 192 (24.7%), R5 71 (9.1%). The positive predictive values for malignancy were R3 32.6%, R4 69.8%, R5 95.8%. Several histologic features of DCIS were associated with R5 rather than R3 radiology: high nuclear grade, solid or cribriform architecture, necrosis, periductal inflammation or fibrosis, and associated microinvasive or invasive carcinoma. Mammographic lesions and histologic whole and invasive tumors increased in size from R3 to R5. Radiologic size of calcifications correlated with whole (but not invasive) tumor size, although it tended to underestimate it by several millimeters. Digital-detected calcifications were more likely than screen-film detected to be categorized as R3 and less likely R4 or R5, and there was no significant difference in positive predictive value between the two imaging techniques in any R-category. In conclusion, histologic features of DCIS, in particular those associated with high grade, are associated with R5 radiology. There is no significant difference in positive predictive value for malignancy in any R-category between digital and screen-film mammography.