**Core Concept**
Tumor markers are substances produced by cancer cells or in response to cancer that can be detected in blood, urine, or other bodily fluids. In the context of hepatocellular carcinoma (HCC), certain tumor markers have been identified to aid in diagnosis and monitoring.

**Why the Correct Answer is Right**
CA-19-9 is a tumor marker primarily associated with pancreatic cancer, not hepatocellular carcinoma (HCC). It is produced by malignant cells of the pancreas and can be elevated in other types of cancer, such as colorectal and gastric cancer. In contrast, other options are directly related to HCC: **AFP (Alpha-fetoprotein)** is a well-established tumor marker for HCC, while **PIVKA-2 (Protein Induced by Vitamin K Absence or Antagonist-II)** is also used in the diagnosis and monitoring of HCC.

**Why Each Wrong Option is Incorrect**
* **Option A:** Neurotensin has been studied as a potential tumor marker for various cancers, including pancreatic, prostate, and breast cancer, but it is not typically associated with HCC.
* **Option D:** PIVKA-2 is indeed a tumor marker for HCC, making it incorrect as an exception.

**Clinical Pearl / High-Yield Fact**
When evaluating tumor markers for HCC, a combination of markers, including AFP, PIVKA-2, and others, may be used to improve diagnostic accuracy and monitor treatment response.

**Correct Answer Line**
✓ Correct Answer: C. CA - 19-9