Early colorectal cancer is defined as cases that remains in the mucosa or submucosa regardless of nodal metastasis. Endoscopic treatment is beneficial for early colorectal cancer without nodal metastasis, and detailed histopathological examination can confirm whether the resection is complete or not. Among early colorectal cancers, those that invade the submucosa are classified as T1, and the nodal metastasis rate is reported to be 9–14.3%     . Pedunculated polyps correspond to Ip in the Paris classification . According to a report by Kida et al., 68% of Ip polyps were adenoma, 25.4% were carcinoma in adenoma, 3.3% were m carcinoma, and the same 3.3% were submucosa-invading (sm) carcinoma. Ip polyps are considered to be curatively resected if they are completely resected, with no cancer cells at the surgical margin, not poorly differentiated, and without lymphovascular invasion . Therefore, Ip polyp rarely requires additional surgical treatment. Kitajima et al. also reported that in Ip sm carcinoma, lymphatic metastasis was 0% in cases of head invasion or cases with a depth of less than SM 3000 µm and no lymphatic invasion. Haggitt et al. classified the infiltration levels of pedunculated malignant polyps into four levels: Level 1: Infiltrative adenocarcinoma localized to the polyp head (infiltration through the lamina muscularis mucosae), Level 2: Neck involvement, Level 3: Cancer cells in the stem, Level 4: Cancer cells infiltrating the submucosal tissue at the level of the adjacent intestinal wall. The Haggitt line is a fictitious border drawn as a baseline to distinguish between head invasion and stalk invasion. If the infiltration level is less than 4, the risk of local recurrence or metastasis is estimated to be low. Tateishi et al. report that the risk of nodal metastasis is increased if any one of lymphatic invasion, poorly or moderately differentiated adenocarcinoma, and the presence or absence of budding is applied. In this case, Haggitt classified it as level 2, but it was poorly differentiated adenocarcinoma, with a depth of SM3500 µm, positive lymphatic invasion, and budding3, and the risk of nodal metastasis was considered to be high. Poorly differentiated colorectal adenocarcinoma is reported to be about 4 to 7% of all colorectal cancers in Japan , but it is often found in advanced cancers. Early cancer, especially cases found in the Paris classification Ip type such as this case, are extremely rare. It is quite rare that additional bowel resection is required for the Paris classification Ip type, and the nodal metastasis rate is about 10% in cases of SM 1000 µm or more, and the remaining 90% has no nodal metastasis. On the other hand, if there are multiple factors that are indicated for additional bowel resection of T1 cancer as in this case, the risk of nodal metastasis may be high. Among poorly differentiated adenocarcinomas, the non-solid type has significantly more nodal metastasis, liver metastasis, and peritoneal dissemination than the solid type, and has a poor prognosis. Considering that laparoscopic surgery has become common recently and less invasive surgery is possible, if there are multiple factors such as SM infiltration distance, lymphatic invasion, budding, etc., it is important to perform additional bowel resection without hesitation rather than deciding the treatment policy based on the Haggitt classification in the Ip type of the Paris classification.
We report a case of pedunculated early colorectal poorly differentiated adenocarcinoma with nodal metastasis, including a review of the literature. This case is expected to be successfully controlled and provides a favorable outcome.