Which type of tumor is classified as benign?

A lipoma is classified as a benign tumor because it is composed of mature fat cells and typically grows slowly. It is usually encapsulated, which means it does not invade surrounding tissues, and it is generally asymptomatic, often discovered incidentally during imaging or physical examination. Unlike malignant tumors, benign tumors such as lipomas do not metastasize to other parts of the body, which is a characteristic feature of malignant tumors.

In contrast, meningiomas can be benign but are categorized differently based on their specific characteristics and location within the brain. Melanoma is a form of skin cancer that is malignant and has a propensity for metastasis. Carcinomas are cancers that arise from epithelial cells and are also classified as malignant. Thus, lipomas stand out as the only benign tumor among the choices presented.