A 55-year-old woman has been steadily gaining weight for the past 30 years. She underwent cholecystectomy for cholelithiasis 5 years ago. She does not smoke. She is now 164 cm (5 ft 4 in) tall and weighs 126 kg (BMI 47). On physical examination, she has a decreased range of motion with pain on movement of the knees. Laboratory studies show a serum glucose level of 176 mg/dL. This patient is at greatest risk of developing which of the following neoplasms?