What is a tumor?

A tumor is characterized as a growth resulting from a mass of abnormal cells that proliferate uncontrollably. This condition occurs when cells in the body begin to grow and divide in an unregulated manner, leading to the formation of a lump or growth. Tumors can be benign (non-cancerous) or malignant (cancerous) depending on their properties, such as the ability to invade nearby tissues or spread to other parts of the body. Understanding the nature of tumors is essential in the study of health and disease, particularly in cancer research and diagnosis.

Other options describe conditions or types of tissue that do not relate to the definition of a tumor. The second option discusses heart function, while the third involves healthy fatty tissue, both of which are unrelated to the concept of tumors. The fourth option refers to viral infections, which are also distinct from the concept of a tumor.