A 73-year-old woman has noticed a 10-kg weight loss in the past 3 months. She is becoming increasingly icteric and has constant vague epigastric pain, nausea, and episodes of bloating and diarrhea. On physical examination, she is afebrile. There is mild tenderness to palpation in the upper abdomen, but bowel sounds are present. Her stool is negative for occult blood. Laboratory findings include a total serum bilirubin concentration of 11.6 mg/dL and a direct bilirubin level of 10.5 mg/dL. Which of the following conditions involving the pancreas is most likely to be present?

The weight loss and pain suggest a malignant neoplasm. Jaundice (a conjugated hyperbilirubinemia) occurs because of biliary tract obstruction by a mass in the head of the pancreas. Such a carcinoma may manifest with "painless jaundice" as well, but it is more likely to invade the nerves around the pancreas, causing pain. Islet cell adenoma is not as common as pancreatic carcinoma. An adenoma located near the ampulla could have an effect similar to that of carcinoma; however, weight loss with adenoma is unlikely. Chronic pancreatitis usually does not obstruct the biliary tract. In cystic fibrosis, there is progressive pancreatic acinar atrophy without a mass effect. Most pseudocysts from pancreatitis are in the region of the body or tail of the pancreas, not the head, and they are nonneoplastic.