Breast cancer and incidence of non-caseating granulomas diagnosed in PET avid chest lymphadenopahy.

e12549 Background: Breast cancer is known to metastasize to the lung parenchyma and lymph nodes. Most breast malignancies are clinically staged using radiographic modalities (e.g. PET scans). Importantly, several inflammatory disorders will present lymph node FDG-uptake on PET, which can be mistaken for breast cancer metastasis. This may alter staging and implicitly treatment for individuals within whom both undiagnosed autoimmune disorders and breast cancer co-occur. We aim to examine the frequency of non-caseating granulomas diagnosed in PET avid mediastinal/hilar nodes in patients with known breast cancer. Methods: Between March 2013 and December 2015, 46 women diagnosed with breast cancer were staged by PET-CT. Those with positive result in the mediastinum/hilum underwent linear endobronchial ultrasound (EBUS) for pathologic diagnosis and ensuing treatment Results: Of the 46 patients with avid mediastinal/hilar adenopathy, 31 (67%) had malignant cytology on EBUS; the remaining 15 had positive PET but negative cytology for malignancy. Twelve of the 15 patients with false positive PET had reactive lymph nodes, and 3 had non-caseating granulomas on cytology (see table). Twenty percent of the patients with negative cytology and positive PET had non-caseating granuloma, and 6.5 % of all patients with positive PET had non-caseating granulomas. Conclusions: To our knowledge, this study represents the largest cohort of breast cancer patients, where the incidence of non-caseating granulomas is investigated in PET-positive mediastinal/hilar nodes. We conclude that in selected patients, in addition to imaging, pathologic staging should be done. Also, the finding of non-caseating granulomas in these patients may either indicate an incidental diagnosis of early stage sarcoidosis, or an inflammatory reaction to the current treatment (sarcomatoid reaction). We also suggest that these patients should be followed for any manifestations of sarcoidosis. [Table: see text]