Hepatocellular carcinoma (HCC) is the most common primary malignancy of the liver and arises predominantly in patients with cirrhosis or chronic hepatitis B. Ultrasound surveillance every six months is recommended for high-risk patients. HCC can appear as a hypoechoic, hyperechoic, or mixed echogenicity mass, and may show a peripheral hypoechoic halo. Doppler may demonstrate internal vascularity. Definitive diagnosis typically requires contrast-enhanced CT, MRI, or biopsy, but ultrasound is the primary surveillance tool.