Neoplastic tumor of the cheek skin, here a benign neoplasm of the sweat glands called Hidradenoma.

A tumor or tumour is the name for a swelling or lesion formed by an abnormal growth of cells (termed neoplastic).^[1] Tumor is not synonymous with cancer. A tumor can be benign, pre-malignant or malignant, whereas cancer is by definition malignant.

[edit] Etymology

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,^[2] all other forms of swelling being called swelling.^[3] This usage is common also in medical literature, where the nouns tumefaction and tumescence, derived from the adjective tumefied, are the current medical terms for non-neoplastic swelling.

[edit] Cause

A neoplasm 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. The nature of the tumor is determined by a pathologist after examination of the tumor tissues from a biopsy or a surgical excision specimen.

[edit] Cases of Contagiousness

Main article: CTVT

In the case of Canine Transmissible Venereal Tumor (CTVT), the tumor cells can actually be contagious. CTVT is a tumor found in the domestic dog (Canis familiaris). It has been theorized and now substantiated that the the infectious agent of this cancer is the cancer cell itself, and that the tumor is clonal in origin. In the case of CTVT, the tumor is passsed through the population by allograft, with the tumor cells from one animal directly seeding tumor formation in the next, usually during coitus^[4].

[edit] References

1. ^ Tumor at Dorland's Medical Dictionary
2. ^ Tumor in MedlinePlus Medical Encyclopedia
3. ^ Swelling in MedlinePlus Medical Encyclopedia
4. ^ VonHoldt BM, Ostrander EA. The singular history of a canine transmissible tumor. Cell. 2006 Aug 11; 126(3):445-7.

[edit] External links

Look up tumor, Tumor, tumour in Wiktionary, the free dictionary.