Disseminated Pulmonary and Hepatic Cystic Echinococcosis Presenting as Suspected Pulmonary Embolism and Mimicking Metastatic Malignancy.

Cystic echinococcosis (CE) is a chronic zoonotic infection caused by Echinococcus granulosus that most commonly affects the liver and lungs. In disseminated disease, the combination of bilateral pulmonary nodules, cavitary consolidation, mediastinal lymphadenopathy, and hepatic lesions can closely mimic metastatic malignancy on cross-sectional imaging and 18F-fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT). This case highlights disseminated CE mimicking pulmonary embolism (PE) and metastatic malignancy. This is a case of a previously healthy 27-year-old woman who presented with acute dyspnea, pleuritic chest pain, fever, and productive cough and was referred for suspected PE; however, CT pulmonary angiography ruled out PE and revealed bilateral pulmonary nodules, cavitary right middle lobe consolidation, mediastinal lymphadenopathy, and multiple hepatic lesions initially interpreted as metastatic malignancy. FDG PET/CT showed intensely hypermetabolic pulmonary and mediastinal disease (SUVmax (maximum standardized uptake value), 15.6), while the hepatic lesions were isometabolic, suggesting a separate etiology. Liver MRI showed well-defined cystic lesions across multiple hepatic segments consistent with hydatid cysts, and Echinococcus serology was positive (titer, 1:640). Bronchoalveolar lavage (BAL) was negative for malignancy and alternative infections. She was treated with albendazole 400 mg twice daily, and five-week follow-up CT showed cavitary transformation of pulmonary nodules consistent with treatment-related cyst degeneration. Disseminated CE can mimic both PE and metastatic malignancy. In patients from endemic regions, discordant FDG PRT/CT findings - hypermetabolic pulmonary lesions with isometabolic hepatic cysts - should prompt consideration of CE. A multidisciplinary approach integrating multimodal imaging and serology is essential for accurate diagnosis and to avoid unnecessary invasive procedures.