Review Question - QID 109835

A 67-year-old man presents to the emergency department with increased fatigue. He has been feeling very tired lately but today lost consciousness while walking up the stairs. He reports mild abdominal distension/discomfort, weight loss, a persistent cough, and multiple episodes of waking up drenched in sweat in the middle of the night. The patient does not see a primary care physician but smokes 2 to 3 packs of cigarettes per day and drinks 1 to 3 alcoholic beverages per day. He recently traveled to Taiwan and Nicaragua. His temperature is 99.5°F (37.5°C), blood pressure is 177/98 mmHg, pulse is 100/min, respirations are 17/min, and oxygen saturation is 98% on room air. The patient is a fatigued-appearing elderly man who is well-groomed. A cardiopulmonary exam reveals mild expiratory wheezes. The abdominal exam is notable for a non-pulsatile mass in the left upper quadrant. Laboratory values are ordered as seen below.

Hemoglobin: 12 g/dL
Hematocrit: 36%
Leukocyte count: 105,500/mm^3
Platelet count: 197,000/mm^3

Serum:
Na+: 139 mEq/L
Cl-: 100 mEq/L
K+: 4.3 mEq/L
HCO3-: 25 mEq/L
BUN: 20 mg/dL
Glucose: 92 mg/dL
Creatinine: 1.4 mg/dL
Ca2+: 10.2 mg/dL
Leukocyte alkaline phosphatase score: 25 (range 20 - 100)
AST: 12 U/L
ALT: 17 U/L

Which of the following is the most likely diagnosis?