Relapse of Rectal Cancer in an Anal Fistula: A Rare Case

Implantation metastasis from sigmoid colon cancer to rectal anastomosis proved by whole exome sequencing and lineage inference for cancer heterogeneity and evolution analysis: Case report and literature review

It was estimated that 70% of patients with colorectal cancer were found to have viable exfoliated malignant cells in adjacent intestinal lumen. Exfoliated malignant cells had been reported to implant on raw surfaces, such as polypectomy site, anal fissure, anal fistula, hemorrhoidectomy wound, and anastomotic suture line. Tumors at anastomosis could be classified into four groups: local recurrence, local manifestation of widespread metastasis, metachronous carcinogenesis, and implantation metastasis. However, all of the previous studies only reported the phenomena of implantation metastasis at anastomosis. No study had proved the origin of anastomotic metastasis by genomic analysis. In this study, a 43-year-old woman presented with persistent hematochezia was diagnosed as having severe mixed hemorrhoids. She was treated by procedure for prolapse and hemorrhoids (PPH), without receiving preoperative colonoscopy. Two months later, she was found to have sigmoid colon cancer by colonoscopy due to continuous hematochezia and received radical sigmoidectomy. Postoperative histological examination confirmed the lesion to be a moderately differentiated adenocarcinoma (pT3N1M0). Six months later, she presented with hematochezia again and colonoscopy revealed two tumors at the rectal anastomosis of PPH. Both tumors were confirmed to be moderately differentiated adenocarcinoma without lymph node and distant metastasis and were finally removed by transanal endoscopic microsurgery (TEM). Pathological examination, whole exome sequencing (WES), and Lineage Inference for Cancer Heterogeneity and Evolution (LICHeE) analysis demonstrated that the two tumors at the rectal anastomosis were probably implantation metastases arising from the previous sigmoid colon cancer. This is the first study to prove implantation metastasis from colon cancer to a distal anastomosis by WES and LICHeE analysis. Therefore, it is recommended to rule out colorectal cancer in proximal large bowel before performing surgery with a rectal anastomosis, such as PPH and anterior resection. For patients with a suspected implanted tumor, WES and LICHeE could be used to differentiate implantation metastasis from metachronous carcinogenesis.

Risk of Anorectal Cancer Associated with Benign Anal Inflammatory Diseases: A Retrospective Matched Cohort Study

Purpose: The purpose of our study was to evaluate the relationship between benign anal inflammatory diseases and anorectal cancer and assess its risk factors. Methods: A retrospective matched cohort study was conducted that included data from 2002 to 2013. The National Health Insurance Service National Sample Cohort data from 2002 to 2013 was used for the study. Of a total study population of 143,884 individuals, 28,110 individuals with anal fissures were assigned to the case group, while 115,774 individuals without anal fissures were assigned to the control group based on the 1:4 propensity score matching age, sex, and year (case: diagnosed year, control: health service received year). Results: The risk of anorectal cancer was higher in the case group (hazard ratio [HR]: 1.95, 95% confidence interval [CI]: 1.51–2.53) compared to the control group. After grouping anorectal cancers into anal cancer and rectal cancer, the risk remained higher in the case group (anal cancer HR: 2.79, 95% CI: 1.48–5.27; rectal cancer HR: 1.82, 95% CI; 1.37–2.42). The case group was further categorized into patients with fissures and patients with fistulas; patients with fissures showed a higher risk of developing anorectal cancer than patients with fistulas (HR: 2.05, 95% CI: 1.53–2.73 vs. HR: 1.73, 95% CI: 1.13–2.66). Study participants in their 30s and 40s had a 4.19- and 7.39-times higher risk of anorectal cancer compared to those in the higher age groups (0.64–1.84), while patients who did not have inflammatory bowel disease (IBD) had a higher risk of developing anorectal cancer (HR: 2.09, 95% CI: 1.56–2.80). Conclusions and Relevance: Patients with anal fistulas or fissures have an increased risk of being diagnosed with anorectal cancer, especially at a young age and even without IBD.

Anal fistula metastasis of rectal cancer after neoadjuvant therapy: a case report

BACKGROUND

Anal metastasis of colorectal cancer is very rare and may present synchronously or metachronously, regardless of pre-existing anal diseases. We report a case of anal fistula metastasis after completion of neoadjuvant therapy for rectal cancer, followed by surgical resection of the primary tumor and metastatic lesion.

CASE PRESENTATION

A 50-year-old man was diagnosed with rectal cancer located 5 cm from the anal verge, with a clinical stage of cT3N0M0. He denied any medical or surgical history, and physical examination revealed no perianal disease. He underwent preoperative chemoradiation therapy (CRT) consisting of a tegafur/gimeracil/oteracil potassium (S-1)-based regimen with 45 Gy of radiation. After completion of CRT, computed tomography (CT) revealed the primary tumor's partial response, but a liver mass highly suggestive of metastasis was detected. This mass was later diagnosed as cavernous hemangioma 3 months after CRT initiation. He then underwent and completed six cycles of consolidation chemotherapy with a capecitabine-based regimen. Subsequent colonoscopy revealed the complete response of the primary tumor, but CT showed thickening of the edematous rectal wall. Therefore, we planned to perform low anterior resection as a radical surgery. However, he presented with persistent anal pain after the last chemotherapy, and magnetic resonance imaging revealed a high-intensity mass behind the anus, suggestive of an anal fistula. We considered the differential diagnosis of a benign anal fistula or implantation metastasis into the anal fistula. Fistulectomy was performed, and a pathological diagnosis of tubular adenocarcinoma, suggestive of implantation metastasis, was made. Thereafter, we performed laparoscopic abdominoperineal resection. Histopathological examination revealed well-differentiated adenocarcinoma, ypT2N0, with a grade 2 therapeutic effect. Subsequent immunohistochemistry of the resected anal fistula showed a CDX-2-positive, CK20-positive, CK7-negative, and GCDFP-15 negative tumor, with implantation metastasis. There was no cancer recurrence 21 months after the radical surgery.

CONCLUSIONS

This is the first report of anal fistula metastasis after neoadjuvant therapy for rectal cancer in a patient without a previous history of anal disease. If an anal fistula is suspected during or after neoadjuvant therapy, physical and radiological assessment, differential diagnosis, and surgical intervention timing for fistula must be carefully discussed.