Background:Intramural metastasis distant from the primary tumor is rare in colorectal cancer. Here, we present a notably rare case of asynchronous intramural recurrence in the rectum after curative surgery for proximal sigmoid colon cancer. To the best of our knowledge, our paper is the first case report of this type of recurrence.Case presentation:A 44-year-old man underwent curative sigmoidectomy for proximal sigmoid colon cancer with tubular adenocarcinomas. The pathological diagnosis was T3N0M0, Stage IIA, according to the 8th Union for International Cancer Control classification. Moderate venous invasion was observed, and all resection margins were negative, including sufficient proximal and distal margins from the tumor.After 15 months, the tumor marker level had increased, and positron emission tomography-computed tomography (PET-CT) revealed abnormal fluorodeoxyglucose uptake in the rectum. Colonoscopy revealed a submucosal tumor (SMT)-like lesion in the upper rectum, and biopsy revealed a tubular adenocarcinoma. We performed curative low anterior resection based on a diagnosis of an atypical primary cancer or a rare case of intramural recurrence. We chose tumor-specific mesorectal excision (TSME) with a distal margin of 3 cm from the tumor. The SMT-like tumor was located approximately 20 cm from the initial sigmoid colon anastomosis (i.e., at least 20 cm distal to the initial sigmoid colon cancer), and pathological findings revealed cancer cells with the same features as the initial sigmoid colon cancer, only in the intestinal wall but not in the mucosa. Therefore, the recurrence was determined to be intramural. Severe venous invasion was also observed, and all resection margins were negative.After 24 months, lung recurrence and local recurrence, which may have involved the lymph nodes in the preserved mesorectum after TSME at the bottom of the pelvis, was detected on PET-CT. We started systemic chemotherapy and stable disease was achieved.Conclusions:This report presented a rare case of asynchronous intramural recurrence in the rectum after curative surgery for proximal sigmoid colon cancer. The discussion regarding the etiology, diagnosis, and optimal surgical procedure to achieve local control for rare intramural recurrence in colorectal cancer should provide valuable information in the clinical setting.

Background Intramural metastasis distant from the primary tumor is rare in colorectal cancer. Here, we present a notably rare and probably the first case of asynchronous intramural recurrence in the rectum after curative surgery for proximal sigmoid colon cancer. Case presentation A 44-year-old man underwent curative sigmoidectomy for proximal sigmoid colon cancer with T3N0M0, Stage IIA tubular adenocarcinomas. After 15 months, the tumor marker level had increased, and positron emission tomography-computed tomography (PET-CT) revealed abnormal fluorodeoxyglucose uptake in the rectum; colonoscopy revealed a submucosal tumor (SMT)-like lesion in the upper rectum, and biopsy revealed a tubular adenocarcinoma. We performed curative low anterior resection with tumor-specific mesorectal excision (TSME). The SMT-like tumor was located approximately 20 cm from the initial sigmoid colon anastomosis (i.e., at least 20 cm distal to the initial sigmoid colon cancer). The pathological findings revealed cancer cells with the same features as the initial sigmoid colon cancer, only in the intestinal wall but not in the mucosa and extramural tissue. Therefore, the lesion was determined to be an intramural recurrence. After 24 months, lung recurrence, and local recurrence, which might have involved the lymph nodes in the preserved mesorectum after TSME at the bottom of the pelvis was detected on PET-CT. Hence, we started systemic chemotherapy. Conclusions This case report suggests that PET-CT and short-interval repeat colonoscopy may help detect a rare intramural recurrence. A long distal margin may be necessary to achieve local control in the rectal resection for intramural recurrence.

Introduction and importance The standard treatment for locally advanced colon cancer (LACC) without distant metastasis is curative surgery followed by adjuvant chemotherapy, but the long-term outcomes of this strategy are not satisfactory. Neoadjuvant chemotherapy (NAC) is a promising novel option to overcome this issue. Tumor regression is an expected effect of NAC for LACC, but pathological complete response (pCR) is rare. In this report, we present a rare case of pCR after NAC with FOLFOX for LACC in the sigmoid colon. Presentation of case A 66-year-old woman presented to our hospital with fever and abdominal pain. The diagnosis was LACC in the sigmoid colon with possible invasion of the uterus and pelvic wall, stage IIIC (T4bN1bM0). Furthermore, the tumor was complicated by diverticulitis. A colostomy was performed, followed by NAC with FOLFOX. Six cycles were completed without significant adverse events, and the lesion shrunk remarkably. We performed a curative sigmoidectomy without any postoperative complications. Pathological examination revealed no viable cancer cells, indicating pCR. Discussion To the best of our knowledge, this is the first report of pCR after NAC for LACC complicated by diverticulitis. Colostomy before NAC, regimen, and cycle of NAC may be the key to this favorable course. Conclusion We present a rare case of pathological complete after neoadjuvant chemotherapy with FOLFOX for locally advanced colon cancer in the sigmoid colon complicated by diverticulitis. Our experience may be valuable in determining the optimal treatment strategy for LACC complicated by diverticulitis.