# Endobiliary metastasis of colorectal cancer: A rare presentation and diagnostic dilemma: A case report

## TL;DR

This case report highlights the rare occurrence of colorectal cancer spreading to the bile duct, which can be hard to diagnose as it looks like a primary bile tumor.

## Contribution

The paper presents a rare case of endobiliary metastasis from colorectal cancer and emphasizes the importance of immunohistochemistry for accurate diagnosis.

## Key findings

- Endobiliary metastasis mimics primary biliary tumors, causing diagnostic challenges.
- Immunohistochemical markers like CDX2 are crucial for confirming metastasis.
- A multidisciplinary approach is needed for accurate diagnosis and management.

## Abstract

Colorectal cancer is a common malignancy with liver metastases frequently encountered. However, endobiliary metastases are extremely rare and can pose significant diagnostic challenges as they can mimic primary biliary tumors.

We report a 66-year-old female who underwent an extended right hemicolectomy for a well-differentiated adenocarcinoma of the transverse colon pT4aN1bM0. Two years after surgery, follow-up imaging revealed intrahepatic biliary dilation and subtle intraductal lesions, along with suspicious splenic nodules. Hepatic MRI confirmed the presence of endoluminal biliary nodules with upstream dilation. Percutaneous biopsy and immunohistochemical analysis showed tumor cells positive for CDX2 and negative for CD20, supported the diagnosis of intrabiliary colonic metastasis.

The clinical and radiological features of endobiliary metastasis can mimic those of primary biliary neoplasms, making accurate diagnosis challenging. While imaging modalities such as multiphasic CT and MRI are invaluable for lesion characterization, definitive diagnosis relies on tissue sampling and immunohistochemical profiling. Recognizing the possibility of endobiliary metastasis in patients with a history of colorectal cancer is crucial for appropriate management.

Increased awareness of endobiliary metastasis as a manifestation of colorectal cancer metastasis is essential for differentiating it from primary biliary tumors, optimizing therapeutic strategies, and ultimately improving patient outcomes.

•Endobiliary metastasis of colorectal cancer is an extremely uncommon phenomenon, often leading to diagnostic challenges.•The radiological features can mimic primary biliary neoplasms like cholangiocarcinoma.•Confirmatory diagnosis relies on immunohistochemical markers which help differentiate it from primary biliary tumors.•A multidisciplinary approach is essential for accurate diagnosis and effective management.

Endobiliary metastasis of colorectal cancer is an extremely uncommon phenomenon, often leading to diagnostic challenges.

The radiological features can mimic primary biliary neoplasms like cholangiocarcinoma.

Confirmatory diagnosis relies on immunohistochemical markers which help differentiate it from primary biliary tumors.

A multidisciplinary approach is essential for accurate diagnosis and effective management.