An abnormal growth; differential diagnosis includes abscess, metaplasia, and neoplasia.
"The doctor ordered a biopsy to determine whether the patient's abdominal mass was a benign tumor or an infectious abscess."
In plain English: A tumor is an abnormal lump of tissue that grows when cells divide too quickly and stop working correctly.
"The doctor ordered an MRI to check for any tumors in his brain."
Usage: In everyday language, use tumor to describe any unusual lump or swelling on the body rather than strictly medical conditions like abscesses or cellular changes. This term is often used interchangeably with cancer in casual conversation, though medically it refers only to an abnormal growth that may be benign or malignant.
The word "tumor" entered Middle English and Old French before arriving in Latin as a term for swelling. It traces its roots back to the same family of words that includes the modern English verb "to throb."