Cancer and tumors occur commonly in chickens. A tumor is defined as an abnormal, uncontrolled, progressive growth of cells that can occur in any tissue or organ. The most frequent types of tumors identified in chickens are lymphoma, ovarian/oviduct adenocarcinoma, and squamous cell carcinoma.
|Tumor type||% Affected|
|Squamous cell carcinoma||11%|
|Interrenal cell adenoma||0%|
Tumors are classified by their point of origin (epithelial or mesenchymal tissue), cell lineage, and whether it is benign (essentially harmless) or malignant (cancerous).
Lymphoid tumors are often associated with or induced by infection with Marek's disease virus
, avian leukosis virus
or reticuloendotheliosis virus (REV)
. Lymphomas can occur in one or more of a variety of different organs and tissues. The number of and types of organs and tissues affected depend on the virus strain and chicken breed and individual genetics. Lymphomas appear as small white or gray, firm and smooth nodular growths, that vary in size. Clinical signs differ depending on the location of these tumor growths.