Malignancy-Associated Sarcoid-Like Reaction in a Case of Triple-Negative Breast Cancer on F-18 Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography.

We describe the case of a 54-year-old woman with triple-negative breast cancer whose baseline F-18 fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT) showed hypermetabolic left breast primary, ipsilateral axillary lymphadenopathy, lung nodules, and mediastinal lymph nodes. Histopathological examination of tissue from mediastinal lymph nodes confirmed a diagnosis of sarcoid-like reaction. Chemotherapy may induce or cause a flare-up of malignancy-associated sarcoid-like reaction. However, in our patient's post-chemotherapy F-18 FDG PET/CT, there was reduction in size and uptake of the mediastinal lymph nodes along with partial response shown by the other lesions. We aim to describe this rare course of malignancy-associated sarcoid-like reaction and highlight the role of F-18 FDG PET-CT in such cases.