**Core Concept**
Hepatoblastoma is a rare malignant tumor that primarily affects children, and early detection is crucial for effective management. The tumor arises from immature hepatocytes and is often associated with genetic mutations, including mutations in the CTNNB1 gene encoding beta-catenin.

**Why the Correct Answer is Right**
Hepatoblastoma is characterized by the presence of specific histopathological features, including fetal hepatocytes, embryonal hepatocytes, and small cell undifferentiated hepatocytes. The presence of these cells, particularly the fetal and embryonal components, is considered a definitive marker for hepatoblastoma. The tumor cells often exhibit a characteristic nuclear morphology, with large nuclei and prominent nucleoli. The embryonal component is particularly significant, as it is a hallmark of hepatoblastoma and helps differentiate it from other pediatric liver tumors, such as hepatocellular carcinoma.

**Why Each Wrong Option is Incorrect**
**Option A:** AFP (alpha-fetoprotein) is a tumor marker commonly elevated in hepatoblastoma, but it is not a definitive marker, as it can also be elevated in other conditions, such as hepatocellular carcinoma and germ cell tumors.

**Option B:** The absence of specific histopathological features, including the presence of fetal and embryonal hepatocytes, does not exclude hepatoblastoma, as the tumor can exhibit a range of histological patterns.

**Option C:** The presence of genetic mutations, including CTNNB1 mutations, is associated with hepatoblastoma, but it is not a definitive marker, as these mutations can also be found in other conditions.

**Clinical Pearl / High-Yield Fact**
The presence of fetal and embryonal hepatocytes in a liver tumor is highly suggestive of hepatoblastoma, and a biopsy should be performed to confirm the diagnosis.

**Correct Answer: C. The presence of specific histopathological features, including fetal and embryonal hepatocytes, is a definitive marker for hepatoblastoma.**