P1.04-003 Incidence of Non-Caseating Granulomas Diagnosed in PET Avid Mediastinal/Hilar Nodes in Patients with Known Breast Cancer

Abstract

Breast cancer is known to metastasize to the lung.. Most breast malignancies are clinically staged using radiographic modalities (e.g. PET scans). Importantly, many inflammatory disorders will present similar lymph node FDG-uptake on PET- as that of metastasized breast cancer. The latter confuses the 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. Between March 2013 and December 2015, 46 patients 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. 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 (table 1). Table 1Results from EBUS Procedure and Resulting Percentage Following Identification of Sarcoid-like SymptomsTotal Number of patients in study: n=46 with positive PETNumber of patientsPercentage of total (all PET positive patients)Percentage among negative patientsPositive EBUS3167.40%Negative EBUS1226.10%80%Negative/Non-caseating granulomas EBUS36.50%20% Open table in a new tab 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. 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 PET may not be sufficient for staging the mediastinum in patients with breast cancer and, in selected patients, pathologic staging should be done. In addition, 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.