A80-3-24 Bilateral Chylothorax and SVC Syndrome in the Setting of Suspected Thoracic Malignancy

Abstract Introduction Pulmonary hyalinizing granuloma (PHG) is a benign, rare, and often misdiagnosed lung disease due to its radiographic resemblance to metastatic or primary thoracic malignancy. Etiology is theorized to be an exaggerated immune response. We present a complex case of bilateral chylothorax in the setting of suspected thoracic malignancy and SVC syndrome, complicated by hypoxic respiratory failure and cardiac arrest. Case Presentation A 81-year-old male with history of CAD (s/p LAD PCI), COPD, and recent STEMI presented with exertional dyspnea, weakness, cough and headaches. Initial chest X-ray revealed a large left-sided pleural effusion; thoracentesis yielded milky exudative triglyceride-rich fluid, consistent with chylothorax, raising concern for thoracic duct obstruction. Cytology was negative. Further CT thorax imaging demonstrated a right suprahilar mass encasing the right upper lobe bronchus with multiple spiculated nodules, compressing the mediastinum. The compression had suggested a component of SVC Syndrome. Diagnostic evaluation included two non-diagnostic EBUS procedures, inconclusive IR-guided biopsy, and repeat cytology - all without definitive malignancy. Bilateral chylothorax, recurrent effusions, and continued dyspnea led to placement of an indwelling pleural catheter. Nutrition was consulted for MCT-enriched diet; however, the patient declined enteral feeding. The patient arrested intraoperatively during VATS procedure with thoracic duct ligation and mass biopsy, requiring CPR and vasopressor support. After multiple cardiac arrests, he was pronounced dead in the CVICU. Postmortem pathology revealed nodular expansion of the interstitium by pulmonary hyalinizing granuloma (PHG). Discussion To our knowledge, there are no prior reports linking pulmonary hyalinizing granuloma to chylothorax. While PHG is known to cause fibrosing pulmonary nodules and may mimic malignancy, this case appears to be the first in which PHG presented with bilateral chylothorax and SVC syndrome, ultimately mimicking thoracic malignancy both clinically and radiographically. In elderly patients with cardiopulmonary comorbidities, bilateral chylothorax without definitive malignancy should raise strong suspicion for other etiologies, such as benign causes masquerading as thoracic malignancy. Early multidisciplinary involvement is essential. Although PHG is rare, this case underscores the limitations of diagnostic accuracy in the setting of nonspecific presentation and association with underlying diseases. This abstract is funded by: None