# Intrahepatic Cholangiocarcinoma Presenting as an Incidentaloma on F-18 PYL PSMA PET/CT

## TL;DR

A patient with prostate cancer was incidentally diagnosed with cholangiocarcinoma using PSMA PET/CT, suggesting a potential new diagnostic tool for this aggressive cancer.

## Contribution

This case report highlights the unexpected detection of cholangiocarcinoma on PSMA PET/CT and suggests its potential diagnostic and therapeutic applications.

## Key findings

- Cholangiocarcinoma was incidentally detected on PSMA PET/CT in a prostate cancer patient.
- PSMA PET/CT may have a role in diagnosing ambiguous cases of cholangiocarcinoma.
- PSMA expression in non-prostate cancers increases the likelihood of incidental diagnosis on PSMA PET scans.

## Abstract

Cholangiocarcinoma is an aggressive malignancy arising from the biliary tract epithelium with rising incidence and mortality. Imaging commonly used for diagnostic workup includes computed tomography (CT) scan and magnetic resonance imaging (MRI). Fluorine-18 fluorodeoxyglucose positron emission tomography (FDG PET) scans can be used for investigating equivocal findings on radiographic imaging. Prostate-specific membrane antigen (PSMA) is known to be highly expressed in prostate adenocarcinoma, allowing it to be leveraged as a target for both imaging and radioligand therapy in prostate cancer. However, PSMA is also commonly expressed in other malignancies such as breast cancer, thyroid carcinomas, and head and neck malignancies, which increase the chances of their incidental diagnosis on PSMA PET scans. Biliary tract cancers, including cholangiocarcinoma, are not commonly expected to be incidentally diagnosed on PSMA PET imaging. Here, we describe the case of a patient with known prostate adenocarcinoma who was later incidentally diagnosed with advanced intrahepatic cholangiocarcinoma on PSMA PET/computed tomography (CT). This case highlights the unexpected finding of cholangiocarcinoma on PSMA PET/CT and suggests further investigation into the role of PSMA PET in diagnosing ambiguous cases of cholangiocarcinoma and its potential theranostic applications.