# A rare case of synchronous anal metastasis from sigmoid adenocarcinoma: case report and literature review

## TL;DR

This paper reports a rare case of anal metastasis from sigmoid cancer without prior anal damage and highlights the need for more clinical data on treatment.

## Contribution

The paper presents a unique case of anal metastasis from colorectal cancer without epithelial damage and emphasizes the need for further research.

## Key findings

- Anal metastasis from colorectal cancer is extremely rare and often occurs on compromised anal epithelium.
- The case involved a 63-year-old male treated with trimodality therapy for synchronous anal metastasis.
- More clinical data is needed to establish effective treatment and postoperative management strategies.

## Abstract

Introduction: Anal metastasis from colorectal cancer is extremely rare, since most cases in the literature are associated with a history of anal disease, such as anal fistula, fissure, hemorrhoidectomy, and anastomotic injury.

Herein, we report the case of a 63-year-old male patient, who presented with synchronous anal metastasis from a sigmoid cancer in the absence of epithelial damage treated with trimodality therapy that consisted of neoadjuvant chemoradiotherapy followed by abdominoperineal resection.

True cutaneous metastases to the anal skin from colonic carcinomas are exceedingly uncommon and are likely underpinned by diverse mechanisms such as lymphatic dissemination, transperitoneal extension, direct extension, retrograde vascular dissemination, or systemic hematogenous spread. This pattern of metastasis is particularly observed in advanced tumor presentations.

This report guides clinicians to think about this rare type of metastasis. However, more clinical data is necessary to establish treatment and postoperative management plan for anal metastasis derived from colorectal cancer.

•Anal metastasis from colon cancer is a rare manifestation, constituting an atypical trajectory for disease progression.•Most reported instances of cancer spread describe implantation on compromised anal epithelium, often associated with anal fistulas or fissures.•This report guides clinicians to think about this rare type of metastasis.•However, more clinical data is necessary to establish treatment and postoperative management plan for anal metastasis derived from colorectal cancer.

Anal metastasis from colon cancer is a rare manifestation, constituting an atypical trajectory for disease progression.

Most reported instances of cancer spread describe implantation on compromised anal epithelium, often associated with anal fistulas or fissures.

This report guides clinicians to think about this rare type of metastasis.

However, more clinical data is necessary to establish treatment and postoperative management plan for anal metastasis derived from colorectal cancer.