Signalment:  
Gross Description:  
Histopathologic Description:
Tumors were specifically stained by a rabbit anti-ALSV serum and two mouse monoclonal antibodies against subgroup A ALSV, and the inner bulb of Herbst corpuscles was strongly stained. Normal cutaneous and subcutaneous tissues of the affected chickens were negative.Â
Electron microscopy revealed viral particles in the tumor that were 74-97 nm in diameter, had a core (34-46 nm in diameter) and envelopes, and sometimes showed the budding process. Their ultrastructural characteristics were identical with those of type C retroviruses.8
Morphologic Diagnosis:  
Lab Results:  
Condition:  
Contributor Comment:  
The tumor contained large amounts of mucin and involved histologic lesions similar to those previously reported in cases of myxoma in chickens2, 16 and was therefore diagnosed as myxoma. Myxoma is composed of embryonal connective tissues.9 Myxoma in the subcutis, spleen, kidney, ovary, and mesentery in chickens has been previously reported.1, 16, 20 Replication-defective avian retroviruses and Rous sarcoma virus affect mesenchymal cells and cause sarcomas.12 Various tumors have been reported in chickens inoculated with specific strains of ALSV; for example, strain F-1A of subgroup A has been associated with lymphoid leukosis, erythroblastosis, fibrosarcoma, and hemangioma in inoculated chickens.7
Today, it seems that leukosis-free flocks have been established, most commercial flocks consist of genetically resistant lines, the eradication of horizontally transmitted viruses has been accomplished,12 and, accordingly, there has been a sharp reduction in the incidence of diseases associated with ALSV infection with the exception of subgroup J ALSV.14,18 However, in our unpublished data, layer flocks frequently have ALSV antigens in Japan, and we are concerned about an outbreak of diseases associated with ALSV. The present epizootic outbreak of neoplastic disease is therefore unusual and worthy of study.
JPC Diagnosis:  
Conference Comment:  
Viruses of the avian leukosis/sarcoma virus (ALSV) group are members of the Alpharetrovirus genus of the family Retroviridae. Other species within this genus include the Rous sarcoma virus and other replication defective viruses that carry various oncogenes. ALSVs are divided into 6 subgroups, A-E and J, based on differences in their viral envelope. Viral replication requires a reverse transcriptase that synthesizes a DNA provirus of the RNA virus. This DNA provirus is then integrated into the host cell genome where viral RNAs are transcribed, which are then translated into precursor and mature viral proteins.
In addition to subgroups, strains of ALSV are generally classified according to the predominant neoplasm they produce, such as lymphoid leukosis virus (LLV), avian erythroblastosis virus (AEV), avian myeloblastosis virus (AMV), and avian sarcoma virus (ASV). Although the oncogenic spectrum of the strains are usually characteristic, they can overlap and are affected by viral origin, dose, and route of inoculation, as well as by host age, genotype, and sex.
Gross and histologic differential diagnoses for neoplasms and lesions that may be caused by ALSV strains include:
- Lymphoid, erythroid, and myeloid infiltrates
- Mareks disease, lymphoid leukosis virus, and reticuloendotheliosis virus have very similar gross and histologic lesions. They may be differentiated via PCR or serology
- Erythroblastosis the liver and bone marrow are usually cherry red
- Myeloblastosis the liver is usually pale red and the bone marrow is whitish, grossly the lesions are similar to lymphoid leukosis
- Myelocytomatosis: Distinctive character and location, is usually nodular and multiple, occurs on the surface of bone in association with the periosteum and near cartilage
- Hemangioma: Wounds, bleeding from feather follicles, hemorrhages, and sarcomas
- Renal tumors: Renal enlargement caused by hematomata, lymphoid leukosis, or accumulation of urates
- Osteopetrosis: Other osteopathies such as rickets, and osteoporosis
- Connective tissue tumors: Granulomas, tuberculosis, pullorum disease
Retrovirus of Animals12
Alpharetrovirus | Avian leukosis viruses, avian carcinoma viruses, avian sarcoma viruses, Rous sarcoma virus, duck spleen necrosis virus |
Betaretrovirus | Mouse mammary tumor virus, Jaagsiekte |
Gammaretrovirus | Feline leukemia virus, feline sarcoma virus, porcine type C virus, many murine leukemia viruses, many murine sarcoma viruses |
Deltaretrovirus | Bovine leukemia virus, human and simian T lymphotropic viruses |
Epsilonretrovirus | Walleye dermal sarcoma virus, walleye epidermal hyperplasia viruses |
Lentivirus | Human immunodeficiency virus, simian immunodeficiency viruses, maedi/visna virus, caprine arthritis-encephalitis virus, feline immunodeficiency virus, equine infectious anemia virus, bovine immunodeficiency virus |
Spumavirus | Bovine, feline, simian, and human foamy viruses |
References:
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4. Ginn PE, Mansell JEKL, Rakich PM: Skin and appendages. In: Jubb, Kennedy, and Palmers Pathology of Domestic Animals, ed. Maxie MG, 5th ed., vol. 1, p. 762. Elsevier Limited, St. Louis, MO, 2007
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8. Jawetz E, Melnick JL, Adelberg EA: Tumor viruses. In: Review of Medical Microbiology, 16th ed., pp. 488-498. Maruzen Asia Ltd., Singapore, 1984
9. Jones TC, Hunt RD, King NW: The skin and its appendages. In: Veterinary Pathology, 6th ed., pp 817-871. Williams and Wilkins, Baltimore, 1997
10. Maxie MG, Robinson WF: Cardiovascular system. In: Jubb, Kennedy, and Palmers Pathology of Domestic Animals, ed. Maxie MG, 5th ed., vol. 3, p. 51. Elsevier Limited, St. Louis, MO, 2007
11. Goldschmidt MH, Hendrick MJ: Tumors of the skin and soft tissues. In: Tumors in Domestic Animals, ed. Meuten DJ, 4th ed., pp. 91-92. Blackwell Publishing, Ames, IA, 2002
12. Murphy FA, Gibbus EPJ, Horzinek MC, Studdert MJ: Retroviridae. In: Veterinary Virology, 3rd ed., pp. 363-389, Academic Press, San Diego, 1999
13. Nakamura K, Higahi T, Yamada M, Imai K, Yamamoto Y: Basophilic intracytoplasmic viral matrix inclusions distributed widely in layer hens affected with avian-leukosis-virus-associated tumours. Avian Pathol 36:53-58, 2007
14. Nakamura K, Ogiso M, Tsukamoto K, Hamazaki N, Hihara H, Yuasa N: Lesions of bone and subcutaneous tumors in chickens 945 bone marrow in myeloid leukosis occurring naturally in adult broiler breeders. Avian Dis 44:215-221, 2000
15. Ono M, Tsukamoto K, Tanimura N, Haritani M, Kimura KM, Suzuki G, Okuda Y, Sato S: An epizootic of subcutaneous tumors associated with subgroup A avian leukosis/sarcoma virus in young layer chickens. Avian Dis 48:940-6, 2004
16. Reece RL: Some observations on naturally occurring neoplasms of domestic fowls in the State of Victoria, Australia (1977-87). Avian Pathol 25:407-447, 1996
17. Spencer JL, Benkel B, Chan M, Nadin-Davis S: Evidence for virus closely related to avian myeloblastosis-associated virus type 1 in a commercial stock of chickens. Avian Pathol 32:383-390, 2003
18. Takami, S, Goryo M, Masegi T, Okada K: Histopathological characteristics of spindle-cell proliferative disease in broiler chickens and its experimental reproduction in specific pathogen-free chickens. J Vet Med Sci 66:231-235, 2004
19. Tsukamoto K, Kono Y, Arai K, Kitahara H, Takahashi K: An enzyme-linked immunosorbent assay for detection of antibodies to exogenous avian leukosis virus. Avian Dis 29:1118-1129, 1985
20. West JL: An avian splenic myxoma. Avian Dis 18:139-141, 1974