A Case of Sarcoid Reaction in Subcarinal Lymph Node in A Postoperative Breast Cancer Diagnosed by Thoracoscopic Biopsy.

Lymph node recurrence is common in patients with breast cancer, and breast surgeons often diagnose it based solely on computed tomography (CT) or fluorine-18 fluorodeoxyglucose positron emission tomography-computed tomography (FDG-PET/CT). In this case report, we present a patient with breast cancer having a false positive lymph node detected by FDG-PET/CT, which was later identified as a sarcoid reaction through thoracoscopic surgery. This pathological diagnosis allowed the patient to avoid unnecessary long-term cancer therapies, such as chemotherapy and hormone therapy.