Incidental lung cancer found on screening breast MRI with eventual lymphatic metastasis to the breast

A 49 year-old female underwent breast MRI for further evaluation of a single projection mammographic finding. MR showed normal breast tissue; however, a 3 cm right lung mass was incidentally discovered, and later confirmed by chest CT. Four years after upper lobectomy, lymphadenectomy, and chemoradiation for stage IIIA non-small cell lung cancer, she presented with a breast rash. Punch biopsy of the breast rash showed metastatic adenocarcinoma consistent with lung primary. One year later, diffuse bilateral breast edema and pleomorphic calcifications were present on mammogram. Pathology revealed multifocal intralymphatic adenocarcinoma, consistent with metastasis from lung primary. This unusual case illustrates an incidentally discovered lung carcinoma found on breast MR that, over time, spread to the breast via the lymphatic system.