Parathyroid Hormone-Related Peptide-Producing Gallbladder Cancer Presenting With Humoral Hypercalcemia of Malignancy: A Case Report

Humoral hypercalcemia of malignancy (HHM) is often reported in cancers derived from the squamous epithelium; however, there are very few reports of HHM in patients with gallbladder cancer. We report a case of a parathyroid hormone-related protein (PTHrP)-producing gallbladder cancer presenting with HHM. A 43-year-old woman presented with appetite loss, nausea, and brown-colored urine. Blood tests revealed that she had hypercalcemia, high serum bilirubin, and high serum parathyroid hormone. Contrast-enhanced computed tomography revealed a gallbladder tumor, liver metastasis, and bile duct obstruction caused by the gallbladder tumor in the hilar region. No bone metastasis was observed. Endoscopic retrograde cholangiopancreatography revealed pancreaticobiliary maljunction. Metal biliary stents were placed, and a transpapillary biopsy of the gallbladder tumor revealed a pathological diagnosis of adenocarcinoma. The patient was diagnosed with HHM due to gallbladder cancer with liver metastasis. Although her hypercalcemia and jaundice improved, her appetite loss and nausea did not improve. Subsequently, the patient developed disseminated intravascular coagulation, and her general condition gradually deteriorated. Due to her poor general condition, chemotherapy could not be administered. The patient died six weeks after visiting our hospital. Although rare, some gallbladder cancers cause HHM due to PTHrP production.