A 65-year-old man consults a physician because he has had severe alternating constipation and diarrhea for the past two months. Hemoccult test on a stool sample is positive for occult blood. Colonoscopy demonstrates a large annular, encircling mass 25 cm above the anal verge, in the descending colon. To which of the following nodes would this tumor be most likely to first metastasize?