Final answer:
The liver lesion primarily composed of blood vessels is a Hemangioma. Other lesions mentioned, such as Adenoma, Focal nodular hyperplasia, and Hepatocellular carcinoma, have different tissue characteristics and are not primarily vascular.
Step-by-step explanation:
The liver lesion that is primarily composed of blood vessels is a Hemangioma. Hemangiomas are benign tumors made up mostly of blood vessels - they are the most common benign liver lesions. The liver, in its normal state, has a rich blood supply from two main sources: the hepatic artery and the hepatic portal vein. Oxygenated blood reaches the liver through the hepatic artery, whereas nutrient-rich deoxygenated blood from digestion arrives via the hepatic portal vein. Within the liver, the blood is processed before leaving via the hepatic vein to join the systemic circulation.
In contrast to Hemangiomas, the other listed lesions represent different tissue alterations. An Adenoma is a benign tumor of epithelial tissue, not primarily vascular. Focal nodular hyperplasia involves the overgrowth of multiple types of liver tissue, and Hepatocellular carcinoma is a malignant tumor that originates from hepatocytes. None of these lesions are characterized by being composed predominantly of blood vessels, which distinguishes a Hemangioma.