Metastatic Breast Cancer Presenting as an Organizing Pneumonia Pattern on Chest CT: A Case Report.

Pulmonary metastasis from breast cancer typically presents as multiple well-defined nodules on chest imaging. Atypical radiological patterns, including air-space consolidation mimicking organizing pneumonia (OP), are exceedingly rare and diagnostically challenging. We report a case of a 68-year-old woman with a history of left breast cancer treated 26 years earlier who developed new bilateral bronchovascular bundle thickening with surrounding ground-glass opacities and consolidation on chest CT, mimicking OP. The patient had been receiving fulvestrant for known pulmonary metastasis diagnosed 14 years prior. A transbronchial biopsy from the left lower lobe revealed adenocarcinoma with positive immunostaining for estrogen receptor and GATA-binding protein 3, consistent with metastatic breast cancer. Treatment with S-1 resulted in radiological improvement at four months. This case adds to the limited literature documenting OP-mimicking pulmonary metastasis from breast cancer and highlights the importance of maintaining a high index of suspicion and pursuing tissue diagnosis in patients with a history of breast cancer who present with new pulmonary infiltrates.