Small Flat Adenocarcinoma of the Colon Arising From Familial Adenomatous Polyposis Patient: Suggesting de novo Origin

ABSTRACT

Most adenocarcinomas of the colorectum arise in a visible benign precursor lesion, the adenoma, which is a monoclonal proliferation of dysplastic nonmalignant epithelial cells. Adenoma-adenocarcinoma sequence has been represented as the predominat pathogenetic pathway. But a small flat depressed colon cancer is characterized by non-polypoid growth pattem with no association of adenomatous tissues, which has tendency to early submucosal invasion and lymph node metastasis even in very small lesion (<10 mm). It supports de novo carcinogenesis of colorectal cancer, although most colorectal cancerarise in pre-existing adenoma. We report a case of small float colon adenocarcinoma arising in normal colonic epithelium rather than adenomatous polyp in familial adenomatous polyposis syndrome.