A Case of Colon Cancer with Extramural Tumor Deposits in the Main Lymph Node Area: A Case Report.

A 72-year-old man with type 2 sub-circumferential tumors in the descending colon and two nodules around the pedicle of the inferior mesenteric artery (main lymph node area) underwent laparoscopic left hemicolectomy with D3 lymphadenectomy. Two lymph nodes around the inferior mesenteric artery pedicle were completely excised. Pathological examination revealed a moderately differentiated tubular adenocarcinoma. Nodules were only found in the main lymph node area, and no lymph node structures were observed in these nodules. These tumor deposits (TDs) may be extramural TDs without lymph node structure or lymph node skip metastasis. The presence of TDs in colorectal cancer is associated with an adverse prognosis, and the requirement of chemotherapy in such cases should be examined. Therefore, it is important to correctly recognize TDs and categorize the disease into a high- or low-risk group within stage III. We report this case because it is necessary to review the definition of TDs, and the assessment of extramural TDs remains controversial.