Discrepant serum and urine β-hCG results due to production of β-hCG by a cribriform-morular variant of thyroid papillary carcinoma

Abstract

BackgroundAlthough patients with medullary thyroid cancer are known to present with paraneoplastic hormone production, this is much less common with papillary thyroid cancer. MethodsWe present a patient with the cribriform morular variant of papillary thyroid cancer in association with familial adenomatous polyposis who developed a positive pregnancy test in the absence of known pregnancy. The patient had developed vaginal bleeding, and her laboratory testing was characterized by elevated serum human chorionic gonadotropin (β-hCG) concentrations, but negative qualitative urine results. After a thorough gynecological evaluation to exclude unexpected normal, ectopic, or molar pregnancy, we pursued an evaluation for other sources of β-hCG production. ResultsWe showed that the elevated serum β-hCG concentrations were not the result of heterophile antibody interferences, and ultimately we proved that her recurrent tumor produced the ectopic β-hCG. This is the first report of β-hCG production by papillary thyroid cancer. Thus, the possibility of ectopic production of β-hCG by papillary thyroid cancer needs to be included in the differential diagnosis of elevated hCG concentration in the absence of pregnancy. ConclusionsThis study of an unusual paraneoplastic syndrome highlights the importance of investigating discrepancies in the clinical laboratory.