A 76-Year-Old Male Was Admitted for Symptoms Including Constipation, Change

A 76-year-old male was admitted for symptoms including constipation, change in stool character and weight loss. Colonoscopy revealed multiple polyps in the rectosigmoid area. An adenomatous polyp was removed. Another colonic tumor was seen in the same patient which was flat with irregular "shaggy rug" surface. A biopsy showed frond-like glandular architecture. Atypical epithelial cells in clusters were seen beneath the muscularis mucosae. The most likely diagnosis is:

A) adenomatous polyp
B) villous adenoma with atypism
C) focus of adenocarcinoma arising in villous adenoma
D) colitis cystica profunda
E) NONE of above