Sole metastatic pulmonary nodules from breast cancer simulating primary lung adenocarcinoma: Two case reports

The characteristic radiological signs of primary lung adenocarcinoma include notching, lobulation, spicular formation, pleural indentation and a bronchus leading to the nodule (bronchus sign). However, metastatic tumors rarely display such characteristics. We herein present two cases of breast cancer with sole metastatic pulmonary tumors recurring ~20 years after surgery for breast cancer. These patients exhibited radiographic signs specific to primary lung adenocarcinoma. Pulmonary metastatic nodular lesions occur through hematogenous spread; therefore, obtaining pathological specimens by transbronchial biopsy may be challenging. In our patients, however, obtaining pathological specimens by transbronchial biopsy was feasible and it ultimately confirmed the diagnosis of lung metastasis from previously treated breast cancer. To the best of our knowledge, no similar cases are reported in the English medical literature. Therefore, metastatic breast cancer may exhibit the characteristic radiological signs of pulmonary lung adenocarcinoma and, although rare, pulmonary metastasis from breast cancer should be considered even in the presence of irregularly shaped pulmonary nodule(s) following long-term disease-free survival.