title: Extranodal lymphoblastic lymphoma of suspected B-cell lineage in the gingiva of a racehorse, accompanied by mandibular osteolysis.
abstract: A mass developed in the mandibular gingiva of a thoroughbred racehorse. When the horse could no longer eat unassisted, it was killed and immediately autopsied. Macroscopically, the mandible exhibited extensive osteolysis, with only a small amount of bone remaining around the tooth roots. The cut surface of the mass around the mandible consisted of neoplastic medullary tissue, in which osteogenesis was observed. The medullary tissue was composed of pleomorphic medium-sized to large cells, interlaced by collagen bundles. These cells had large, pale, round or ovoid, sometimes cleaved nuclei, with one or two prominent nucleoli. Mitoses were numerous. Electron microscopy showed that the cells in the medullary tissues were similar in shape to undifferentiated lymphocytes. Immunohistochemically, these cells were positive for B-cell associated antigen in the pre-B-cell stage. Our findings suggest that the horse had extranodal lymphoblastic lymphoma of suspected B-cell lineage, possibly originating from the lymphatic system of the gingiva. We consider that the osteolysis resulted from activation of osteoclasts by proliferation of the tumour cells.
authors.affiliation: Addresses of authors: Equine Research Institute, Japan Racing Association, 321-4 Tokami, Utsunomiya, Tochigi, 320-0856, Japan. masaaki_oikawa@jra.go.jp
authors.forename: M
authors.initials: M
authors.lastname: Oikawa
authors.forename: H
authors.initials: H
authors.lastname: Ohishi
authors.forename: Y
authors.initials: Y
authors.lastname: Katayama
authors.forename: A
authors.initials: A
authors.lastname: Kushiro
authors.forename: H
authors.initials: H
authors.lastname: Yoshikawa
authors.forename: T
authors.initials: T
authors.lastname: Yoshikawa
mesh_terms: D000818:Animals; D001344:Autopsy; D003937:Diagnosis, Differential; D005260:Female; D005887:Gingival Neoplasms / Q000150:complications / Q000175:diagnosis / Q000662:veterinary*; D006734:Horse Diseases / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000473:pathology; D006736:Horses; D007150:Immunohistochemistry / Q000662:veterinary; D008336:Mandibular Diseases / Q000150:complications / Q000175:diagnosis / Q000662:veterinary*; D010014:Osteolysis / Q000150:complications / Q000175:diagnosis / Q000662:veterinary*; D010805:Physical Conditioning, Animal; D054198:Precursor Cell Lymphoblastic Leukemia-Lymphoma / Q000150:complications / Q000175:diagnosis / Q000662:veterinary*; D011859:Radiography