Tumor markers such as carbohydrate antigen 19-9 (CA 19-9) are commonly measured in the serum of patients with suspected pancreaticobiliary malignancies. Moderate elevations of CA 19-9 may be seen in benign disease, but levels in the thousands are indicative of malignancy. We report the case of a 64-year-old man with an elevated CA 19-9 of 5791 U/ml and radiological findings suggestive of metastatic gallbladder carcinoma. The patient underwent cholecystectomy and excision of a common bile duct stricture, with hepaticojejunostomy and liver biopsy. The final surgical pathology was consistent with xanthogranulomatous cholecystitis (XGC) and the elevated CA 19-9 returned to normal postoperatively. Thus, an elevated CA 19-9 level, even in the thousands, should not preclude patients from an operation if a mass is deemed resectable. Thorough investigation and treatment may result in a curative operation even if unresectable malignant disease is initially suspected.