Metastasis to the breast.

Cross-lymphatic metastasis from one breast to the other is the most frequent type of metastatic involvement of the breast. Melanoma, lung, ovary, and sarcoma are the most common types of blood-borne metastases to the breast from extramammary sites. The most common radiographic findings in patients with blood-borne metastases to the breast are single or multiple discrete nodules. Lymphoma or leukemia may involve the breast primarily but more often as part of a widespread process. Their presentation varies from discrete to ill-defined masses and may be obscured by underlying benign proliferative changes.