Castleman's disease is an unusual inflammatory lymphoproliferative disorder of unknown cause. It most commonly occurs in the mediastinum but rarely in the axillary lymph nodes. We report a case of localized axillary Castleman's disease mimicking metastasis as the patient had a palpable malignant mass in the breast, described by ultrasonography, color Doppler ultrasonography, contrast-enhanced CT, and dynamic enhanced breast MR images.