Paragonimiasis Mimicking Malignancy: A Case Report of a Diagnostic Challenge in Pulmonary Nodule Evaluation.

Paragonimiasis is a parasitic infection that can closely mimic lung malignancy on imaging, creating a significant diagnostic challenge. We report the case of a 60-year-old man from South Korea who presented with hemoptysis and was found to have a suspicious pulmonary nodule. Despite antibiotic therapy and serial imaging, the nodule persisted, and the patient subsequently developed a large pleural effusion. Radiologic findings raised concern for malignancy; however, noninvasive diagnostic evaluations were inconclusive. The patient ultimately underwent video-assisted thoracoscopic surgery, which revealed diffuse pleural thickening and numerous parasitic ova. Histopathologic and laboratory findings confirmed paragonimiasis. Following treatment with praziquantel, the patient achieved full clinical recovery. This case illustrates the potential for paragonimiasis to mimic malignancy and underscores the importance of including parasitic infections in the differential diagnosis, particularly in endemic regions. In selected cases, surgical intervention may be required to establish a definitive diagnosis.