Interval growth of probably benign breast lesions on follow-up ultrasound: How can these be managed?

Objectives: To investigate the malignancy rate in probably benign lesions with interval growth on follow-up ultrasound (US) and the cut-off values for predicting malignancy. Methods: By retrospective reviewing 19,435 US examinations assessed as probably benign lesions, a total of 214 lesions with interval growth in 199 patients were included. The increased volume (%V),%V per month, the most increased diameter (D), and D per month were compared between malignant and benign lesions. Malignancy rates were compared between lesions with or without newly developed suspicious malignant features. Results: Twenty-two (10.3%) malignancies showed significant increase in%V,%V per month, D, and D per month compared with 192 (89.7%) benign lesions (p=0.0083, <0.0001, <0.0001, and <0.0001, respectively). Fifteen (38.5%) of 39 lesions where suspicious features developed proved malignant, whereas 7 (4%) out of 175 without were malignant (p=0.0011). In nodules without suspicious features, 24.2% of%V per month and 1.9 mm of D per month showed high sensitivity (85.7% and 71.4%) and specificity (67.8% and 97.6%) for predicting malignancy. Conclusions: Probably benign lesions with interval growth should undergo prompt biopsy because of the 10.3% malignancy rate. In lesions where suspicious features developed, the malignancy rate increased to 38.5%.