Abstract

Hematopoietic malignancies, particularly lymphoproliferative disorders, are the most common neoplasms in lizards. Although not uncommon, the occurrence of these tumors in reptiles is typically sporadic. This report describes an unusually high incidence of lymphoid neoplasia in Egyptian spiny-tailed lizards (Uromastyx aegyptius) over an 8-yr period. Between 1993–2001, eight out of 15 (53%) lizards necropsied at the Louisville Zoological Garden were diagnosed with multicentric lymphoma. By light and electron microscopic examination, the neoplasms had plasmacytoid morphology suggesting B-cell origin, although some tumors also had a primitive blast cell component. A concurrent leukemic blood profile was identified in seven out of the eight cases. All were adult animals and no sex predilection was observed. A review of the case study and an environmental survey did not reveal exposure to any known exogenous carcinogens. Some of the lizards were unrelated, suggesting that hereditary factors were unlikely. Although examination via electron microscopy and viral isolation performed on archived tissues and plasma failed to detect viruses, an infectious etiology is suspected. At the time of this writing, immunohistochemical staining is pending to further characterize the neoplastic cell morphology in this case cluster.