Breast metastasis from extra-mammary malignancy is extremely rare with an incidence from 0.4% to 1.3%. Several types of malignancies that most commonly metastasize to the breast include leukemia, lymphoma, and melanoma. Aim. We report a case of a 57-year-old male with a history of non-small cell lung cancer (NSCLC) who manifested a left breast mass, two years and four months after the initial diagnosis and treatRomament of NSCLC. Method. Physical examination revealed a poorly defined mass in the upper outer quadrant of the left breast, suspicious for breast cancer. After mammography results, the patient underwent Fine Needle Aspiration that was indicative of cancer. He underwent then modified radical mastectomy and axillary lymph node dissection. Histology and immunohistochemical analyses were conducted, that revealed a NSCLC that metastasized to the left breast. Results. Finally, the prognosis of the patient was poor, as NSCLC relapsed from IIB to stage IV. Conclusions. An accurate differentiation of metastasis to the breast from primary breast cancer is of paramount importance because the therapeutic approach and prognosis of the two differ significantly.
KEY WORDS: Lung cancer - NSCLC - Breast metastasis - Immunohistochemistry - Thyroid transcription factor-1 (TTF1) - Ker7 - Ker20.