The halo sign and malignant breast lesions.

The halo sign, described as a complete or partial radiolucent ring surrounding the periphery of a breast mass, has long been considered a mammographic sign indicating a benign process. The phenomenon is most frequently seen with cysts and fibroadenomas. Over the past 8 years, 25 malignant breast lesions with a partial or complete halo on mammography have been identified in 19 women. These cases suggest that a halo sign does not guarantee a benign process.