PURPOSE: Although the screening with a mammography has been shown to reduce breast cancer mortality, it has limitations relating to its sensitivity and efficacy. Interval cancers are those that become symptomatic, and are detected between screening
examinations. The success of a screening program in reducing the rate of mortality due to breast cancer relies on keeping the number of interval cancers at a minimum. This study was performed to review the mammographic features of interval cancers, and
to compare their clinicopathological factors with those cancers detected by screening. METHODS: Of the 881 women who had operations for breast cancer performed between 1995 and 1999, we retrospectively analyzed the medical records and mammograms of 57
who received at least a mammogram before the diagnosis of their breast cancer. These patients were divided into an interval cancer group, who had symptoms, and a screen detected cancer group, who had not. The factors compared included the clinical,
radiographic, histopathological, and immunohistochemical features. RESULTS: Interval cancers were more likely to have masses, than microcalcifications, in their mammographic features, and were more likely to be invasive and at a higher stage according
to their histopathological features. The false negative rate was 48% for the screen detected cancers, and 35% for the interval cancers (P=0.414). HRT users had the higher false negative rate of 51.6% than the 26.9% for the nonuser (P=0.103). CONCLUSION:
The interval cancers were found to be different from the screen detected cancers in terms of their radiological and pathological features. The standardization of screen interval, and additional magnification mammography, or ultrasonography may
contribute to reduce false negative rates of mammography.
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