False-positive human serum chorionic gonadotropin in a patient with a history of germ cell cancer

Tumor markers, including the beta-subunit of human chorionic gonadotropin (beta-hCG), and radiological imaging methods are commonly used for the diagnosis and monitoring of testicular cancer. We report of a patient with a history of classical seminoma stage I who had elevated serum levels of beta-hCG suggesting relapse 5 years after initial treatment. Radiological evaluation revealed a pericardial cyst, which was surgically removed. Histological evaluation did not demonstrate malignant tissue, suggesting a false-positive beta-hCG. Further workup confirmed this suspicion as we could demonstrate false-positive test results due to heterophilic antibodies detectable in the patient's serum. This case stresses the need for verification of beta-hCG levels in patients where clinical results are not in line with laboratory results.