Early Pedunculated Colorectal Cancer with Nodal Metastasis: A Case Report

Background: Among early colorectal cancers, pedunculated polyps have a higher complete resection rate than non-pedunculated cases and rarely require additional surgery. However, this time, we experienced a case of pedunculated colorectal cancer, which was histologically poorly differentiated adenocarcinoma. Lymphatic invasion was also found, so additional intestinal resection was performed and nodal metastasis was found. Case presentation: A 43-year-old woman underwent colonoscopy because of positive fecal occult blood. A 20 mm-sized pedunculated polyp was found in the descending colon, and endoscopic resection was performed. Histopathological examination revealed non-solid poorly differentiated adenocarcinoma, invading to the submucosa (3,500 μm from the muscularis mucosae) with lymphatic invasion. In spite of its early stage cancer, the risk of nodal metastasis was considered to be high, and bowel resection was additionally performed. Although there was no residual cancer in the site after endoscopic resection, a metastasis was found in one regional lymph node. The patient is undergoing postoperative adjuvant chemotherapy. There was no evidence of recurrence after three months after the additional surgery. Conclusions: For pedunculated polyps, additional bowel resection was performed for patients with multiple risk factors for nodal metastasis such as poorly differentiated adenocarcinoma and positive lymphatic invasion. Then, we experienced a case of nodal metastasis, so we report it with a review of the literature.

A 20 mm-sized pedunculated polyp was found in the descending colon, and endoscopic resection was performed. Histopathological examination revealed non-solid poorly differentiated adenocarcinoma, invading to the submucosa (3,500 μm from the muscularis mucosae) with lymphatic invasion. In spite of its early stage cancer, the risk of nodal metastasis was considered to be high, and bowel resection was additionally performed. Although there was no residual cancer in the site after endoscopic resection, a metastasis was found in one regional lymph node. The patient is undergoing postoperative adjuvant chemotherapy. There was no evidence of recurrence after three months after the additional surgery.
Conclusions: For pedunculated polyps, additional bowel resection was performed for patients with multiple risk factors for nodal metastasis such as poorly differentiated adenocarcinoma and positive lymphatic invasion. Then, we experienced a case of nodal metastasis, so we report it with a review of the literature.

Background
Endoscopic treatment is useful for early colorectal cancer. In particular, pedunculated polyps have a higher complete resection rate than non-pedunculated polyps, and pedunculated polyps rarely require additional bowel resection. In addition, poorly differentiated adenocarcinoma is rarely detected at an early stage. We report a case of pedunculated early colorectal poorly differentiated adenocarcinoma with nodal metastasis.

Case Presentation
A 43-year-old woman underwent colonoscopy because of positive fecal occult blood. A 20 mm-sized pedunculated polyp was found in the descending colon, and endoscopic resection was performed at local hospital. Histopathological examination revealed non-solid poorly differentiated adenocarcinoma, invading to the submucosa (3,500 µm from the muscularis mucosae) with lymphatic invasion. There was an indication for additional bowel resection, and she was referred to our hospital for surgical treatment.
Physical ndings: Height 163 cm, weight 86.1 kg, body mass index (BMI) 32 kg / m 2 , slightly obese, and abdominal ndings were not particularly noteworthy. All the laboratory tests were not remarkable. Tumor markers including carcinoembryonic antigen (CEA) and carbohydrate antigen 19 − 9 (CA19-9) were within normal limit. Endoscopic ndings: A 20 mm-sized pedunculated polyp was found in the descending colon, with a depression at the apex (Fig. 1). Computed tomography (CT): Neither lymph nodal nor distant metastasis was observed. Based on the preoperative diagnosis of descending colon cancer (cT1bN0M0, clinical stage I), laparoscopic descending colectomy and regional lymph node dissection were performed.
The course was good and she was discharged six days after the operation. Histopathological examination: The tumor itself was a non-solid, poorly differentiated adenocarcinoma with adenoma around it. According to the Haggitt classi cation, level 2 ( Fig. 2), positive lymphatic invasion (Fig. 3), and budding 3. No residual cancer was found in the site after endoscopic resection, and the patient was diagnosed as early-stage cancer, but metastasis was found in one regional lymph node. Pathologically, the cancer was classi ed as T1bN1aM0 StageIIIA according to the TNM classi cation, and postoperative adjuvant chemotherapy with oral S-1 was performed.

Discussion And Conclusions
Early colorectal cancer is de ned as cases that remains in the mucosa or submucosa regardless of nodal metastasis [1]. Endoscopic treatment is bene cial for early colorectal cancer without nodal metastasis, and detailed histopathological examination can con rm whether the resection is complete or not. Cancer cells in the stem, Level 4: Cancer cells in ltrating the submucosal tissue at the level of the adjacent intestinal wall [12]. The Haggitt line is a ctitious border drawn as a baseline to distinguish between head invasion and stalk invasion. If the in ltration 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 [4]. In this case, Haggitt classi ed 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 [13] [14], but it is often found in advanced cancers. Early cancer, especially cases found in the Paris classi cation Ip type such as this case, are extremely rare. It is quite rare that additional bowel resection is required for the Paris classi cation 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 [15] 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 signi cantly 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 [16], if there are multiple factors such as SM in ltration 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 classi cation in the Ip type of the Paris classi cation.
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. con rmed that no ethical approval is required. Consent was obtained from the patient for participation in this study.

Consent for publication
We obtained the patient's consent for publication of this case report.

Availability of data and materials
All data generated or analyzed during this study are included in this published article.

Competing interests
The authors declare that they have no competing interests.

Funding
None of the authors have any funding to disclose.
Authors' contributions HK drafted the manuscript, and SY performed the preoperative investigation. SY and YN provided academic advice. HK, HA and SY performed the operation. YN and TY made a pathological evaluation. All authors have read and approved the nal manuscript. Figure 1 Colonoscopic ndings A 20 mm-sized pedunculated polyp was found in the descending colon, with a depression at the apex of the head.  Podoplanin immunostaining (20x). Multiple tumor cells are found in the lympharics.