Proliferation of leukocyte-forming tissue; the basis of leukemia.
- avian l. — a complex of related diseases caused by retroviruses (oncornaviruses). lymphoid leukosis, erythroblastosis, myelocytomatosis and myeloblastosis are the principal component diseases. There are in addition a series of tumors of connective tissue, epithelium, endothelium and other miscellaneous related tumors.
- cutaneous bovine l. — see bovine viral leukosis.
- enzootic bovine l. — see bovine viral leukosis.
- l.-sarcoma neoplastic diseases — includes lymphoid leukosis, erythroblastosis, myeloblastosis, myelocytomatosis, connective tissue tumors, nephroma, nephroblastoma, miscellaneous epithelial and endothelial tumors, osteopetrosis of birds caused by avian type C oncoviruses.