Metastatic disease in the breast.
Breast cancer is the commonest malignancy in women. However, metastatic involvement of the breast is relatively rare. Metastatic disease of the breast is therefore often an unexpected diagnosis in a female patient presenting with a breast mass. The commonest cause is spread from a contralateral breast carcinoma. Of solid tumors at other sites, the most common cancers to metastasize to the breast are, in declining order of frequency, malignant melanoma, lymphoma, lung cancer, ovarian carcinoma, soft tissue sarcoma, and gastrointestinal and genitourinary tumors. Besides these, metastases from osteosarcoma, thyroid neoplasms, and cervical, vaginal and endometrial carcinomas to the breast have been sporadically reported in the literature. A clinical presentation with pain, tenderness and discharge is distinctly unusual. A solitary lesion is the most common clinical presentation. Lesions that metastasize to the breast may produce changes that look similar to those of primary breast cancer on mammography, but they are more likely to be multiple, are frequently bilateral, and form a nidus of tumor cells that are usually round with fairly well-defined margins. Microcalcifications are not a distinguishing feature, and although their margins may be ill defined, spiculations are not commonly found. Diagnosis is generally achieved by means of fine-needle aspiration cytology or open biopsy of the breast masses. In recent reports, particular importance has been attached to the performance of fine-needle aspiration cytology diagnosis, to differentiate a metastasis from a second primary tumor, thus making it possible to avoid unnecessary mastectomy and ensure that appropriate chemotherapy and radiotherapy are implemented.