Fig. 3.

A case of a small, indistinct mass on mammography but no abnormal findings on ultrasound. a, b Mammography: small indistinct mass (allow), SMC. Screening ultrasound: no abnormality, SUC 1. The overall assessment category: SC 4. c Targeted ultrasound: indistinct mass with interruption of the anterior border of the mammary gland and halo sign (4 mm), DUC4. Histopathology: invasive ductal carcinoma. This case is difficult to detect based on screening ultrasound, especially when performing ultrasound without reference to mammography findings (separate mammography/ultrasound method) (SMC screening mammography category, SUC screening ultrasound category, SC screening category, DUC diagnostic ultrasound category)