Metachronous isolated breast metastasis from pulmonary adenocarcinoma with micropapillary component causing diagnostic challenges

BACKGROUND: Breast metastasis from extramammary malignancy is uncommon and often presents diagnostic challenges. Herein, we report a case of a patient with metachronous isolated breast metastasis from pulmonary adenocarcinoma with micropapillary component. CASE PRESENTATION: A 47-year-old woman presented with left breast nodule detected on a screening breast ultrasonography. She had surgery for pulmonary adenocarcinoma 3 years ago, and was disease-free state in the follow up studies. The patient was diagnosed with invasive micropapillary carcinoma of the breast by core needle biopsy. She underwent left breast lumpectomy and sentinel lymph node biopsy, and the histologic findings revealed micropapillary carcinoma. Based on the immunohistochemical study, the final diagnosis was solitary breast metastasis from pulmonary adenocarcinoma with micropapillary component. CONCLUSIONS: The diagnosis of metastasis to the breast from extramammary malignancies is difficult but important for proper management and prediction of prognosis. A careful clinical history with a thorough clinical examination is needed to make the correct diagnosis.