Sarcoidosis is a systemic granulomatous disorder of unknown origin that affects the lungs and mediastinal lymph nodes in most patients. The coexistence of sarcoidosis and breast cancer has been reported. An unfortunate consequence of the presence of both entities in the same patient is the risk of misdiagnosis. We report the case of a 70-year-old female with T1N0 cancer of the right breast that was initially diagnosed as stage IV because of mediastinal positron-emission tomography - positive lymphadenopathy. Biopsy of a mediastinal lymph node allowed us to diagnose sarcoidosis and correctly stage her disease as stage I breast cancer.
