Abstract: Background: The differential diagnoses of a circumscribed mass of the liver are varied. Especially if a malignant tumor, capable of setting metastases to the liver, is known in a patient's medical history, there might be difficulties in differentiating the tumor's entity.
Casuistry: We report a case of a 40-year-old male with a history of malignant melanoma in whom follow-up investigations revealed a mass in the liver.
Results: The histopathological and microbiological results, however, showed an infestation of liver tissue with nematodes. Malignant tumor cells could not be detected.
Conclusions: Roundworm-infections of the liver can present as lesions suspicious of being malignant. Therefore, along with e.g. microhamartoma, microabscesses and hepatocellular carcinoma, infestation with nematodes should be taken into consideration.