# Distal Cholangiocarcinoma with Synchronous Intramural Bile Duct Metastasis: A Case Report

## TL;DR

A rare case of multiple bile duct tumors was found to be a single cancer with metastasis, not separate cancers.

## Contribution

The paper presents a unique case of synchronous intramural bile duct metastasis in distal cholangiocarcinoma.

## Key findings

- Two tumors were found to be connected through immunohistochemical and pathological evidence.
- The smaller tumor was identified as a metastasis of the larger tumor rather than an independent lesion.

## Abstract

Distal cholangiocarcinoma is a malignant tumor that arises from the epithelial cells of the bile duct. Several risk factors associated with cholangiocarcinoma have been identified. Multiple distal cholangiocarcinomas may occur in patients with several risk factors for cholangiocarcinoma. However, synchronous multiple distal cholangiocarcinomas in the absence of risk factors are rare. Here, we presented a case of multiple tumors on the bile duct diagnosed as distal cholangiocarcinoma with synchronous intramural bile duct metastasis.

A 67-year-old man was referred to our hospital for evaluation of jaundice. Contrast-enhanced computed tomography revealed an enhanced tumor on the common bile duct. Endoscopic retrograde cholangiography showed bile duct stenosis due to a nodular tumor of the common bile duct. We performed subtotal stomach-preserving pancreaticoduodenectomy under diagnosing distal cholangiocarcinoma. The patient was discharged on the 23rd postoperative day. Macroscopic findings of the resected specimen showed a 27-mm nodular-infiltrating tumor at the middle bile duct and a 3-mm nodular tumor at the lower bile duct. The distance between the tumors was 10 mm. Pathological examination revealed that the larger tumor was primarily composed of poorly differentiated adenocarcinoma, with a moderately differentiated component at the periphery of the tumor. The smaller tumor was entirely composed of poorly differentiated adenocarcinoma, which was similar to the poorly differentiated component of the larger tumor. Additionally, microscopic lymphovascular infiltration was observed in the vicinity of both tumors. These two lesions were separated by nontumoral biliary epithelia without atypia. The results of immunohistochemical staining using CK7/20, MUC1/2, and p53 antibodies substantiated the homology of these tumors. These results suggested that the smaller tumor was synchronous intramural bile duct metastasis of distal cholangiocarcinoma rather than independent multiple lesions.

In the cases of multiple tumors being synchronously identified on the bile duct, it is crucial to ascertain the relationship between those tumors. Recent developments in immunohistochemical staining and genetic analysis may further facilitate the assessment of the association between multiple distal cholangiocarcinomas.