SESSION TITLE: Top Posters - Electronic session SESSION TYPE: Original Investigation Poster PRESENTED ON: Monday, October 30, 2017 at 12:00 PM - 01:30 PM PURPOSE: To compare the clinical and imaging features of rheumatoid pulmonary nodules with lung malignancy among rheumatoid patients. METHODS: We retrospectively identified 79 rheumatoid patients with lung nodules encountered at Mayo Clinic, Rochester, MN from January 2001 to June 2016. The diagnosis of rheumatoid pulmonary nodule was evidenced by histopathology and the exclusion of other potential causes including infection and vasculitis. Medical records were reviewed. A retrospective blinded review of CT/FDG PET-CT for both biopsy-proven rheumatoid and other pulmonary nodules in rheumatoid patients using MIM software was performed (MIM Software Inc, Beachwood, Ohio). Imaging was also reviewed by a senior radiology trainee and a nuclear/thoracic radiologist with 10 years of clinical experience with board certification in radiology and nuclear medicine. RESULTS: Among the entire cohort, there were 44 (56%) females with a mean age of 67.3±10.9 years. There were 64 (81%) previous/current smokers with a mean pack history of 37.8±27.3 years. Subcutaneous rheumatoid nodules were observed in 24 (30%) and rheumatoid factor seropositivity in 47 (60%). Histologic diagnoses included 50 malignancies (63%; 40 non-small cell lung cancer, 4 small cell lung cancer, 2 carcinoid and 4 metastatic disease from extrapulmonary primary), 23 RA pulmonary nodules (29%), 3 histoplasmosis and 3 benign (2 amyloid and 1 respiratory bronchiolitis). Compared to malignancies, patients with rheumatoid pulmonary nodules were characterized by younger age (p<0.001), less smoking exposure (p=0.005), increased likelihood for subcutaneous rheumatoid nodules (p<0.001), and rheumatoid factor seropositivity (p=0.034). Imaging features of RA pulmonary nodules included smooth borders (p=0.004), satellite nodules (p<0.001), cavitation (p=0.003), and subpleural location with subpleural rind (p=0.033). Malignant nodules were more likely to be spiculated (50% vs 13%, p=0.008). PET-CT was available to review for 47 malignancies and 7 rheumatoid pulmonary nodules. Mean SUV and SUVmax were lower for rheumatoid pulmonary nodules (2.03±1.23 vs 3.96±2.2, p=0.035; 3.03±1.9 vs 7.15±4.8, p=0.022, respectively). FDG-avid or enlarged draining lymph nodes were observed in 10% of malignancy but none of the rheumatoid pulmonary nodules (p=0.301). CONCLUSIONS: Among rheumatoid patients with pulmonary nodules, clinical and imaging features may distinguish rheumatoid pulmonary nodules from malignancy. Patients with rheumatoid pulmonary nodules are younger with less smoking exposure and more likely to demonstrate subcutaneous rheumatoid nodules and seropositivity. Imaging of rheumatoid pulmonary nodules demonstrates nodules which are multiple in number with smooth borders, cavitation, satellite nodules and subpleural location with occasional subpleural rind. They are rarely spiculated in contrast to malignancy. They tend to have lower FDG avidity without enlarged or FDG avid draining lymph nodes. CLINICAL IMPLICATIONS: Clinical and imaging features may help distinguish rheumatoid pulmonary nodules from malignancies in rheumatoid patients. DISCLOSURE: The following authors have nothing to disclose: Matthew Koslow, Jason R. Young, Misbah Baqir, Joanne E. Yi, Geoffrey Johnson, Jay Ryu No Product/Research Disclosure Information