Paragonimiasis westermani presenting as an asymptomatic nodular lesion in the lung: report of a case.

A 57-year-old man with a history of having consumed fresh-water crab 8 months previously presented with a solitary mass lesion in the left lung without any symptoms. Since neoplastic disease could not be ruled out, an open biopsy was performed, and histological examination confirmed a definite diagnosis of paragonimiasis. A high level of the anti-Paragonimus westermani antibody was detected in the sera of the patient, but this level decreased substantially 3 months after chemotherapy with bithionol.