Sonographically Depicted Breast Clustered Microcysts: Is Follow-Up Appropriate?

The objective of this study was to evaluate outcomes of lesions prospectively classified on breast sonography as clustered microcysts without a discrete solid component. Over a 4-year interval during which 1,900 consecutive breast sonography examinations were obtained at the University of Maryland, 110 examinations (5.8%) yielded 123 lesions so classified. Sonography was performed by a physician using a linear-array broadband transducer (L7.5-12 or L7-13 MHz). Follow-up of at least 24 months was available for 66 lesions, and 14-gauge core biopsy was performed on another 13 lesions. The median patient age was 48 years (range, 32-71 years), and the median lesion size was 8 mm (range, 5-30 mm). Of the 79 lesions with acceptable follow-up, all were depicted sonographically, 57 (72%) were seen mammographically, and four (5%) were palpable. Of the 13 lesions biopsied, five (38%) showed apocrine metaplasia; five (38%), fibrocystic changes; two (15%), cysts; and one (8%), a microscopic fibroadenoma and cysts. Of the 66 lesions with 2-year follow-up, 35 (53%) were stable, 15 (23%) had resolved, 12 (18%) decreased, and four (6%) minimally increased at 1 year and were then stable (n = 2) or decreased (n = 2) after 2 subsequent years. Fusion of several small cystic spaces was seen in one (2%) of the lesions followed. Breast clustered microcysts are relatively common, seen in 5.8% of breast sonograms. In our series of 79 lesions with follow-up, none proved malignant: Follow-up on an annual basis appears reasonable for most such lesions. Validation of this approach across multiple centers is needed.