[单选] 68岁男性门诊就诊时发现巩膜黄染。自述近期发现尿液颜色加深，粪便颜色变浅；伴有食欲减退但无其他特殊不适。既往史无明显异常，吸烟史30年，已戒13年。查体，体温及生命体征正常。确诊有黄疸，在右上腹部可触及一个无痛性，光滑的圆形肿块。其它检查未见异常。该患者最可能的诊断为？A 68-year-old man presents to the clinic with yellow eyes． He has recently noticed his urine is dark and his stool is light in color． In addition， he has had a diminished appetite but otherwise is feeling well without other complaints． Past medical history is unremarkable． He has smoked for 30 years but quit 13 years ago． On examination， he is afebrile and his vitals are normal． He is jaundiced and during examination of his abdomen， a nontender smooth globular mass was found in the RUQ． The rest of the examination is normal． What is the most likely diagnosis for this patient？