Background: Women with small mammographically detected breast cancers generally have good long-term outcomes, but a few with T1a (1-5 mm) and T1b (6-10 mm) tumours will eventually die from breast cancer. We investigated whether women at high risk of breast-cancer death could be identified with mammographic criteria and differentiated from women with small cancers of the breast and good outcomes. Methods: We prospectively applied mammographic classifications of tumour type to a consecutive series of 343 mammograms of invasive breast cancers of size 1-14 mm. Classifications were: stellate (spiculated) mass with no calcifications; circular or oval lesions with no calcifications; spiculated or circular lesions with non-casting-type calcifications; and casting-type calcifications: Findings: 20-year survival for women with 1-14 mm invasive tumours with casting-type calcifications was 55%. 14% of 138 women with 1-9 mm tumours had casting-type calcifications on mammography, which accounted for 73% of all breast-cancer deaths (p <0.001). T1a, T1b, and 10-14 mm tumours with casting-type calcifications behaved as if they were larger lesions, since the rate of death was similar to that for women with advanced high-grade tumours. Most women who died were node-negative. The long-term survival of women who had tumours of 1-9 mm with no casting-type calcifications was about 95%. Interpretation: Mammographic classification seemed to reliably predict good and bad long-term outcomes for survival in tumours of 14 mm or smaller, and especially for those smaller than 10 mm. The implications for therapy are substantial.
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