A new study in the American Journal of Roentgenology aimed to study the malignancy rate of lesions in the breast, identified as clustered microcysts, a common find on breast ultrasound.

The retrospective study was led by Heather Greenwood, MD, assistant professor of clinical radiology, breast imaging section at the University of California, San Francisco.

Using electronic medical records (EMRs) and PACS, the researchers identified cases from 2013 of lesions marked as “clustered microcysts” or “clusters of microcysts.” The researchers used BI-RADS definition of clustered microcysts. In keeping with prior studies, cysts measured between two millimeters and five millimeters were used in the study. Outcomes and frequency of malignancy were determined by reviewing the electronic medical records and PACS.

Mammography and ultrasound reports were reviewed for lesions that met the researcher’s criteria. Factors such as shape, margins, largest dimension, clinical history, risk factors and menopausal status were recorded. For postmenopausal patients, the use of hormone therapy was also included.

• Patients studied had an average age of 50.
• 93 patients with 95 lesions were researched.
• 16 lesions had biopsies, and 12 of those had additional satisfactory follow up.
• 14 of the lesions were benign.
• 91 lesions had at least 24 months of imaging follow-up, with an average follow up of 56 months.
• One lesion had a decrease in size.

None of the 95 lesions showed malignancy.

“These results are consistent with those of prior studies, which showed that the risk of malignancy for clustered microcysts is extremely low to nonexistent,” the authors wrote.

The authors added that given a less than two percent of malignancy overall, the results indicate that biopsies can be avoided and such cases can be assigned as “BI-RADS 3” or probably benign. Short-term imaging follow-up may be appropriate.