Myelocytoma in a 24-day-old Commercial Broiler
Saad Gharaibeh,1 Tom Brown,1 Pedro Villegas,2 and Alberto Botero3
1Departments of Veterinary Pathology and Avian Medicine, College of Veterinary Medicine, The University of Georgia, Athens, Georgia (USA)30602; 2Department of Avian Medicine, College of Veterinary Medicine, The University of Georgia, Athens, Georgia (USA) 30602; and 3Avidesa Company, Colombia.
Abstract: A myelocytoma was diagnosed on the head of 24-day-old commercial broiler chicken. The neoplastic myelocytes were present as a subepithelial mass over the skull.
Key Words: Myelocytoma, ALV-J, Chicken, Tumor, Head, Retrovirus, Virus.
Introduction
Myelocytomas were first described as avian leukosis virus (ALV)-associated tumors of adult chickens. 1 Virus particles were demonstrated in these tumors by transmission electron microscopy. 2 After the recognition of a new ALV subgroup J, this subgroup is believed to cause myelocytomatosis, renal adenomas, histiocytic sarcoma, mesothelioma, granulosa cell tumors, pancreatic adenocarcinoma, and other neoplasms in younger chickens. 3,4 This manuscript briefly describes a rapidly developing myelocytoma in a young chicken.
Case Report
A myelocytoma was diagnosed on the head of a 24-day-old commercial broiler chicken from a flock with high incidence of tumor formation. Gross examination revealed a mass on the surface of the skull (Fig. 1).
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| Fig. 1. A dome-shaped mass is present over the top of the skull. |
On histologic examination, the mass was non-encapsulated and consisted of a pleomorphic population of myeloid cells arranged in sheets. Myeloid cells also infiltrated the surrounding tissues. The mass was covered by intact feathered skin. Individual neoplastic cells had ill defined boundaries and moderate amounts of cytoplasm with numerous round, intensely eosinophilic granules (Fig. 2). Nuclei were single, round, and vesicular. The neoplastic cells exhibited both anisokaryosis and anisocytosis. The mitotic index was 2-4 mitoses / 40x field of view. Multiple, variably-sized bone spicules and woven bone lined by osteoblasts were present throughout the mass (Fig. 3). In addition, a moderate scirrhous reaction was observed. Multifocal lymphocytic nodules also were present within the mass and the superficial dermis (Fig. 4).
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| Fig. 2. Myelocytoma, Chicken, H&E stain. Neoplastic myeloid cells contain moderate amounts of cytoplasm with eosinophilicgranules. |
Fig. 3. Myelocytoma, Chicken, H&E stain. Spicules of bone within the neoplasm. |
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Fig. 4. Myelocytoma, Chicken, H&E stain. A lymphoid
nodule is present surrounded by neoplastic myeloid cells. |
References
1. Campbell JG: Tumors of the Fowl. Philadelphia, J. B. Lippincott Company. 1969.
2. Ivanov X, Maldenov Z, Nedyalkov S, Bozhkov: Electron-microscope proof of virus particles in fowl myelocytomatosis. Dokl Bolg Akad Nauk 18: 593-595, 1965.
3. Payne LN, Fadly AM: Leukosis/sarcoma group. In Calnek BW (ed): Diseases of Poultry, 10th ed. Ames, Iowa State University Press. 1997, pp. 414-466.
4. Payne LN, Gillespie AM, Howes K: Myeloid leukaemogenicity and transmission of the HPRS-103 strain of avian leukosis virus. Leukemia 6:1167-1176, 1992.
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