Screening interval breast cancers: mammographic features and prognosis factors.

PURPOSE: To review the mammographic features of screening interval breast cancers and to compare the tumor size, histologic grade, and lymph node involvement with those in screening-detected and unscreened symptomatic cancers. MATERIALS AND METHODS: Screening mammography was performed in 72,773 women aged 50-64 years. Ninety interval cancers were identified in 89 women. The mammographic and histopathologic features of these cancers were analyzed. RESULTS: At review of the screening mammograms, interval cancers were classified into four groups: 51 true-positive, 20 false-negative, seven mammographically occult, and 12 unclassified. The most common missed abnormality in the false-negative cases was architectural distortion. Interval cancers were larger, of higher grade, and more likely to have lymph node involvement than screening-detected tumors and were of similar size, histologic grade, and stage of lymph node involvement as symptomatic tumors. CONCLUSION: Prognosis in interval cancers is similar to that in symptomatic, unscreened tumors and statistically significantly worse than that in screening-detected cancers.