Opening label, dynamic prospective cohort study on the small focus less than 1.0 cm shown by type B ultrasound in breast.

Background: A consensus has not been achieved regarding the treatment of small nonpalpable breast lesions, and the purpose of this study was to prospectively investigate nonpalpable lesions less than 1.0 cm in diameter to explore the risk factors for such lesions and determine appropriate treatment of such kind of lesions. Methods: A total of 1039 patients with small lesions less than 1.0 cm in diameter who underwent mammography and ultrasound from 2009 to 2010 in our institution were prospectively enrolled. Among them, 80 patients underwent biopsy, whose lesions grew by more than 30% of its original size, with an unclear boundary or irregular shape. All patients were followed-up for an average of 24 months, and lesions identified as high-risk types, such as cancer or atypical hyperplasia, of tumors on pathological examination were labeled "meaningful lesions." Then relevant factors affecting the detection of meaningful lesions were analyzed. Results: In total, 40 meaningful lesions including 2 breast cancers were detected, accounting for 3.8% and 0.2% of all patients, respectively. Univariate analysis identified smoking (P = .030), irregular shape (P = .018), unclear boundary (P = .024), and vascularization (P = .023) as risk factors for the detection of meaningful lesions (P < .05). On multivariate analysis, smoking and irregular shape were further identified as independent risk factors for the detection of meaningful lesions. Conclusion: The overall incidence of cancer among nonpalpable lesions with a diameter less than 1.0 cm is low. Biopsies are strongly recommended for patients who are smokers or who have small lesions with an irregular shape, whereas regular follow-up observation is likely safe for other patients with small, non-palpable breast lesions.