A tumor, or neoplasm, is a mass of abnormal cells that can form in tissues, glands, organs, skin, or bone. Tumors can be benign (noncancerous), malignant (cancerous), or precancerous. While benign tumors are usually harmless and localized, malignant tumors can spread (metastasize) and may be life-threatening. Precancerous tumors may turn cancerous if untreated.

Tumors vs. Cysts

Tumors are solid masses of tissue, while cysts are sacs filled with fluid, air, or other material. Most cysts are noncancerous.

Symptoms of Tumors

Symptoms vary but may include:

• Fatigue
• Fever or chills
• Night sweats
• Unexplained weight loss
• Painful or firm lumps

Causes of Tumors

Tumors develop when abnormal cells multiply or fail to die as expected, resulting in an overgrowth or mass.