Breast metastasis from lung cancer: a report of two cases and literature review.

Breast metastasis from extra-mammary malignancy is rare. An incidence of 0.4% to 1.3% has been reported in literature. The primary malignancies that most commonly metastasize to the breast are leukemia, lymphoma, and malignant melanoma. In this report, two cases of pulmonary metastasis to the breast were presented. A 40-year-old female manifested a right breast mass of 2-month duration. After physical examination was performed, a poorly defined mass was noted in the upper outer quadrant of the right breast. Another 49-year-old female manifested right breast mass of 5-day duration. A poorly defined mass was noted in the lower inner quadrant of the right breast. Mammography results also revealed breast cancer. The patients underwent local excision. After histological and immunohistochemical analyses were conducted, a primary lung carcinoma that metastasized to the breast was diagnosed. An accurate differentiation of metastasis to the breast from primary breast cancer is very important because the treatment and prognosis of the two differ significantly.