Objectives: The objective of this study was to identify clinical and imaging features that distinguish rheumatoid lung nodules from malignancy. Methods: We conducted a retrospective review of 73 rheumatoid patients with histologically-proven rheumatoid and malignant lung nodules encountered at Mayo Clinic, Rochester, MN (2001–2016). Medical records and imaging were reviewed including a retrospective blinded review of CT and PET/CT studies. Results: The study cohort had a mean age of 67 ± 11 years (range 45–86) including 44 (60%) women, 82% with a smoking history, 38% with subcutaneous rheumatoid nodules, and 78% with rheumatoid factor seropositivity. Subjects with rheumatoid lung nodules compared to malignancy were younger (59 ± 12 vs 71 ± 9 years, p < 0.001), more likely to manifest subcutaneous rheumatoid nodules (73% vs 20%, p < 0.001) and rheumatoid factor seropositivity (93% vs 68%, p = 0.034) but a history of smoking was common in both groups (p = 0.36). CT features more commonly associated with rheumatoid lung nodules compared to malignancy included multiplicity, smooth border, cavitation, satellite nodules, pleural contact, and a subpleural rind of soft tissue. Optimal sensitivity (77%) and specificity (92%) (AUC 0.85, CI 0.75–0.94) for rheumatoid lung nodule were obtained with ≥ 3 CT findings (≥ 4 nodules, peripheral location, cavitation, satellite nodules, smooth border, and subpleural rind). Key 18 FDG-PET/CT features included low-level metabolism (SUV max 2.7 ± 2 vs 7.2 ± 4.8, p = 0.007) and lack of 18 F-fluorodeoxyglucose (FDG)-avid draining lymph nodes. Conclusion: Rheumatoid lung nodules have distinct CT and PET/CT features compared to malignancy. Patients with rheumatoid lung nodules are younger and more likely to manifest subcutaneous rheumatoid nodules and seropositivity. Key Points: • Rheumatoid lung nodules have distinct clinical and imaging features compared to lung malignancy. • CT features of rheumatoid lung nodules include multiplicity, cavitation, satellite nodules, smooth border, peripheral location, and subpleural rind. • Key PET/CT features include low-level metabolism and lack of FDG-avid draining lymph nodes.
- Multidetector computed tomography
- Multiple pulmonary nodules
- PET-CT scan
- Rheumatoid arthritis
- Rheumatoid nodule
ASJC Scopus subject areas
- Radiology Nuclear Medicine and imaging