Depressed-type of early colon cancer with extensive lymph node metastasis

Early colorectal cancer (ECC) is defined as invasive tumor limited to the colonic and rectal mucosa or submucosa, regardless of the presence or absence of lymph node metastasis. The incidence of lymph node metastasis in ECC ranges from 0 to 15.4%, and risk factors include depth of submucosal invasion, growth patterns (polypoid or non-polypoid), histologic subclassification, and lymphatic invasion. Of non-polypoid growth patterns, the depressed types of colorectal cancer have higher malignant potential than polypoid types, even for small sizes. Unfortunately, this type is also difficult to detect on colonoscopic examination. In this report, we describe a case of depressed type ECC with extensive lymph node metastasis without regional lymph node involvement.