Introduction: Lung adenocarcinoma is the most common type of lung cancer. Distant metastasis of lung adenocarcinoma often occurs in multiple organs. The common metastasis sites of lung cancer include the lungs, brain, bones, adrenal glands, and lymph nodes; however, breast metastasis is rare.
Patient concerns: In this report, we describe a case of breast metastasis from lung adenocarcinoma. A 55-year-old woman reported left breast pain for more than 1 month.
Diagnosis: Based on imaging, pathological examination, and immunohistochemical examination, the diagnosis of breast metastasis from lung adenocarcinoma was confirmed. Epidermal growth factor receptor mutations and anaplastic lymphoma kinase rearrangement were not detected by next-generation sequencing.
Interventions: The patient was treated with six courses of a combination of albumin-bound paclitaxel, cisplatin, and bevacizumab over 21 days.
Outcomes: After six cycles of palliative chemotherapy, her left breast pain and swelling subsided; in addition, her serum CA12-5, CYFRA, and CEA levels normalized by April 2019. PR status was evaluated as per the RECIST 1.1 criteria. The patient developed brain metastases 3 months later and died due to multiple organ failure.
Conclusion: The possibility of breast metastasis should be considered in patients with existing malignant tumors and breast pain. Clinical and imaging examinations are helpful for diagnosis, and pathological and immunohistochemical analyses are the most important diagnostic tools.