**Core Concept**
Klatskin tumor is a rare type of cholangiocarcinoma, a malignancy of the bile duct epithelium, typically occurring at the junction of the right and left hepatic bile ducts. This anatomical location is crucial for its clinical presentation and management.

**Why the Correct Answer is Right**
Klatskin tumor is characterized by its location at the hepatic duct confluence, leading to obstruction of both the right and left hepatic ducts. This results in jaundice, pruritus, and potentially, secondary biliary cirrhosis. The tumor's growth pattern and location make surgical resection challenging, often requiring a multidisciplinary approach.

**Why Each Wrong Option is Incorrect**
**Option A:** Klatskin tumor is not a type of pancreatic cancer. While pancreatic cancer can involve the bile ducts, Klatskin tumor is a distinct entity originating from the bile duct epithelium.
**Option B:** Klatskin tumor is not a type of liver metastasis. Liver metastases are secondary deposits from a primary cancer elsewhere, whereas Klatskin tumor is a primary malignancy of the bile ducts.
**Option C:** Klatskin tumor is not synonymous with hilar cholangiocarcinoma. While both terms refer to bile duct malignancies at the hepatic duct confluence, Klatskin tumor specifically refers to tumors at this location, whereas hilar cholangiocarcinoma is a broader term.

**Clinical Pearl / High-Yield Fact**
The term "Klatskin tumor" was coined by Dr. David Klatskin, who first described this entity in 1965. Recognizing the distinct clinical and pathological features of Klatskin tumor is essential for accurate diagnosis and management.

**Correct Answer: D. Klatskin tumor**