A 57-year-old man presents complaining of a change in stools over the last 4 months. His stools are intermittently bloody, and he has experienced a decline in his appetite associated with a 15-pound unintentional loss of weight. Which of the following is the most likely explanation for his symptoms?
Adenocarcinoma of the colon
Gastrointestinal carcinoid tumor
Primary colorectal lymphoma
Squamous cell carcinoma of the colon
