C52-21 Malignant Pericardial Effusion Uncovered During Chronic Obstructive Pulmonary Disease (COPD) Exacerbation: A Case of Metastatic Adenocarcinoma of Unknown Primary

Abstract Introduction Malignant pericardial effusion is a rare but life-threatening manifestation of metastatic cancer. Lung, breast, and gastrointestinal malignancies account for most cases. Early recognition and drainage are lifesaving and can establish the diagnosis. We describe an unusual presentation of metastatic adenocarcinoma of unknown primary, initially mistaken for a chronic obstructive pulmonary disease (COPD) exacerbation. Case Report A 58-year-old woman with hypertension, Graves’ disease, prior intracranial aneurysm repair, and COPD presented with progressive shortness of breath and chest tightness for four days. She was tachycardic with new-onset atrial fibrillation with rapid ventricular response and hypoxemia. She was initially treated for a COPD exacerbation with community-acquired pneumonia.Computed tomography pulmonary angiogram excluded pulmonary embolism but revealed a large, complex pericardial effusion, right lower lobe pneumonia, and right middle lobe collapse. Transthoracic echocardiography confirmed cardiac tamponade physiology. Emergent pericardiocentesis drained hemorrhagic fluid. Cytology of the pericardial fluid showed malignant adenocarcinoma cells. Immunohistochemistry was positive for MOC31, BerEP4, CK7, CK20, and faint thyroid transcription factor-1 (TTF-1), and negative for GATA3, PAX8, and CDX2, suggesting possible lung, pancreatobiliary, or upper gastrointestinal origin.Computed tomography of the chest, abdomen, and pelvis demonstrated an irregular right lower lobe opacity suspicious for primary lung cancer, an anterior abdominal wall mass measuring 1.8 × 3.3 cm, and a cystic lesion near the sacrum measuring 4.5 × 1.8 cm. The patient was diagnosed with metastatic adenocarcinoma of unknown primary, Stage IV by definition due to malignant pericardial effusion. She improved following pericardiocentesis and supportive COPD management. Pathology from an anterior abdominal wall biopsy was pending at discharge. Discussion This case emphasizes that dyspnea in a patient with COPD may not always represent an exacerbation. The presence of unexplained tachyarrhythmia, chest discomfort, or discordant imaging findings should prompt evaluation for alternative etiologies such as pericardial effusion. Malignant pericardial effusion can mimic pulmonary pathology and may be the first clue to an occult malignancy. Integration of imaging, cytology, and immunohistochemistry is crucial for establishing the diagnosis and guiding management. Conclusion COPD exacerbations can unmask underlying malignancy. Clinicians should maintain a broad differential for acute dyspnea, as early recognition and drainage of malignant pericardial effusion are lifesaving and may reveal metastatic disease. This abstract is funded by: None