A tumor or tumour is the name for a swelling or lesion formed by an abnormal growth of cells (termed neoplastic). Tumor is not synonymous with cancer. A tumor can be benign, pre-malignant or malignant, whereas cancer is by definition malignant.
The term tumor is derived, via the Old French tumour
, from the Latin tumor
"swelling". It originally meant an abnormal swelling of the flesh. In contemporary English, tumor is synonymous with solid neoplasm
, all other forms of swelling being called swelling
. This usage is common also in medical literature, where the nouns tumefaction
, derived from the adjective tumefied
, are the current medical terms for non-neoplastic swelling.
is an abnormal proliferation of tissues, usually caused by genetic mutations
. Most neoplasms cause a tumor, with a few exceptions like leukemia
or carcinoma in situ
Tumors may be benign, pre-malignant or malignant (cancer). The nature of the tumor is determined by a pathologist after examination of the tumor tissues from a biopsy or a surgical excision specimen.