A solid tumor is an abnormal mass of tissue that usually does not contain cysts or liquid areas. Solid tumors may be benign (not cancer), or malignant (cancer). Solid tumor types are named according to the type of cell they originate from. Examples of solid tumors are sarcomas, carcinomas, and lymphomas. Leukaemias (cancers of the blood) generally do not form solid tumours.
The word tumor does not always imply cancer. In discussing tumors that are malignant (cancerous), however, the term solid tumor is used to distinguish between a localized mass of tissue and leukemia.