tumor definitions
Medical Definition of Tumor Our Tumor (Grade) Main Article provides a comprehensive look at the who, what, when and how of Tumor (Grade) Tumor: An abnormal mass of tissue. Tumors are a classic sign of inflammation, and can be benign or malignant (cancerous). There are dozens of different types of tumors. Their names usually reflect the kind of tissue they arise in, and may also tell you something about their shape or how they grow.