Detection of Non-Palpable Breast Cancer in Mass Screening with Real-Time Whole Breast Scanning

Our system of screening for breast cancer ensures that all the women involved are examined by real-time ultrasonography (US). A total of 23, 235 women with an average age of 47 yr were examined by real-time whole breast scanning (WBS). Approximately 18 examinations per hour were carried out. Of the total women participating, 8, 540 (36%) were examined by MMG in addition to WBS. Later the same day, US-guided aspiration cytology was performed on any lesions that had been detected by WBS. Fifty-nine breast cancers were detected, among which 29 (49%) were non-palpable. The rate of detection was 0.25%, which was double that for palpation only. WBS detected 22 non-palpable breast cancers, whereas MMG detected 7. The 22 cancers detected by WBS included 16 small invasive carcinomas, in comparison with only one invasive carcinoma found among the 7 cancers detected by MMG. It is important to note that most non-palpable breast cancers do not demonstrate the classic characteristics of malignancy, but often appear as stains, irregular mottled areas, fat-like masses, or adenoma-like masses. We cannot diagnose small non-palpable breast cancers on the basis of US findings alone. Therefore it is important to perform US-guided aspiration cytology on every lesion, even those which are found to be virtually benign. It is generally thought that MMG is superior to US with regard to the detection of non-palpable breast cancer. However, the technology of US has developed considerably, and we consider that mass screening with real-time whole breast scanning has great potential.