# Eosinophilic cholangitis misdiagnosed as cholangiocarcinoma: a case report

## TL;DR

A rare case of eosinophilic cholangitis was misdiagnosed as cholangiocarcinoma but confirmed through histopathology and successfully treated with steroids.

## Contribution

This case report provides a rare definitive pathological confirmation of eosinophilic cholangitis.

## Key findings

- EC was confirmed via histopathology showing dense eosinophilic infiltration in the bile duct wall.
- Symptoms resolved completely after methylprednisolone therapy with no recurrence in 3 months.
- EC should be considered in cases of biliary obstruction with unexplained eosinophilia.

## Abstract

Eosinophilic cholangitis (EC) has a low clinical incidence, and cases with definitive pathological confirmation are extremely rare. Due to the lack of specificity in clinical and radiologic features, EC is frequently misdiagnosed as cholangiocarcinoma. We report a 65-year-old man admitted with progressive jaundice and persistent dull right upper-quadrant abdominal pain for more than 1 month. Laboratory tests showed a markedly elevated peripheral blood eosinophil count, significantly elevated bilirubin levels, and elevated tumor markers. MRI revealed intra- and extrahepatic bile duct dilatation and common bile duct wall thickening. Cholangiocarcinoma was initially suspected. A radical pancreaticoduodenectomy was planned. However, intraoperative exploration showed edema and induration of the bile duct and pancreas. Therefore, the radical resection was aborted, and bile duct wall biopsy alone was performed for pathological diagnosis. Postoperative histopathology revealed dense eosinophilic infiltration in the bile duct wall (>20 eosinophils per high-power field), confirming the diagnosis of EC. After postoperative standard methylprednisolone therapy, the patient achieved complete symptom resolution. Laboratory indices returned to the normal range, and no recurrence was observed during the 3-month follow-up. This case highlights that EC should be suspected in biliary obstruction with unexplained eosinophilia, and histopathology is the key to definitive diagnosis.