A case report of paraneoplastic syndrome in β-hCG-secreting duodenal adenocarcinoma

Human chorionic gonadotropin (hCG) is a glycoprotein hormone that is used in clinical practice to detect pregnancy and serves as a sensitive marker for trophoblastic tumors. Other organs besides placental trophoblasts naturally express the hormone at low levels, which can be elevated in nontrophoblastic malignancies. Some studies have suggested that elevated β-hCG levels in nontrophoblastic tumors are a sign of aggressive disease and strongly associated with poor prognosis. We describe a case of a 50-year-old post-menopausal woman with metastatic duodenal adenocarcinoma who presented with a negative pregnancy test that later changed to positive. Biopsy of the primary duodenal mass showed positive immunohistochemical expression of β-hCG. The patient was also found to have multiple brain metastases, which is uncommon in gastrointestinal cancer. This is a rare case of paraneoplastic syndrome in a β-hCG-secreting duodenal adenocarcinoma.