A80-3-42 A Diagnostic Twist: Cryptogenic Organizing Pneumonia Masquerading as Malignancy

Abstract Introduction Cryptogenic organizing pneumonia (COP) is a condition in which alveolar injury causes organized granulation tissue that obstructs alveoli and bronchioles. It is a rare pulmonary disorder with clinical manifestations including cough, dyspnea, and weight loss. Radiographic findings in COP can closely resemble those of malignant lesions, often prompting extensive diagnostic work-up. We present a case of COP in which radiographic findings mimicked metastatic disease, leading to an extensive malignancy workup. Case Presentation A 64-year-old Asian male who is a former smoker presented with left-sided rib pain, productive cough with blood-tinged sputum, weight loss of 30 pounds in two months, and constipation of two weeks. Computed tomography with angiography (CTA) of the chest was negative for pulmonary embolism, however, revealed multiple bilateral pulmonary masses, with the largest in the right upper lobe and left basilar pleural-based mass, findings consistent with probable neoplastic process [Image 1]. Based upon these findings, the patient was evaluated for primary lung adenocarcinoma versus metastatic disease, as well as for tuberculosis due to its high regional prevalence. Computed tomography (CT) of the head, abdomen, and pelvis were obtained to evaluate for potential metastatic disease, however, results were negative. Acid-fast bacilli of the sputum were obtained and results were negative for tuberculosis. CT-guided needle biopsy of the right and left upper lobe masses were obtained to evaluate for tissue diagnosis of suspected malignancy. Pathology results were significant for benign lung parenchyma with organizing pneumonia with chronic inflammation and negative for malignant cells. With malignancy being the leading differential, there were persistent concerns for incorrect sampling, which led to repeat biopsy from a different nodule with confirmation of benign organizing pneumonia. A subsequent PET scan showed minimal tracer uptake in the pulmonary nodules, with no evidence of malignancy. Discussion Distinguishing COP from primary lung cancer or metastatic disease can be challenging due to overlapping radiographic features. Lung cancers are often recognized as irregular nodules or masses with uncertain boundaries; whereas, COP presents in the form of solid or mixed density. A characteristic radiologic feature of COP is the reverse halo sign, also known as the “atoll sign.” It is characterized by central ground-glass opacifications and peripheral or broncho-centric consolidation. In contrast, lung cancers frequently present with lymphadenopathy or pleural effusions. This case underscores the challenge of distinguishing COP from malignancy and emphasizes the need to include COP in the differential diagnosis to limit unnecessary testing and invasive procedures. This abstract is funded by: None