A 58-year-old man with a 3-month history of painless jaundice, weight loss, and pale stools presents to the outpatient clinic. Serum bilirubin is elevated at 8.2 mg/dL with conjugated predominance. Abdominal ultrasound shows a hypoechoic lesion in the pancreatic head with dilated intrahepatic bile ducts. What is the investigation of choice for tissue diagnosis and staging of suspected pancreatic cancer?