Cytomorphological similarities between feline viral leukemia, bovine enzootic leukosis and adult T-cell leukemia/lymphoma: A review

Leukemias are malignant neoplasms of hematological origin and originating from bone marrow cells. Innumerable species can be affected by this disease, which can be originated by several causes, including infection by viruses belonging to the Retroviridae family. In felines, humans and cattle, the leukemia-inducing retroviruses are Feline Leukemia Virus (FeLV), human T-cell lymphotropic virus type 1 (HTLV-1) and Bovine Leukosis Virus (BLV), respectively. In Brazil, the number of domestic cats infected with FeLV grows progressively, when compared to the incidence of infected animals in developed countries, such as the United States. In cattle, viral leukemia or enzootic bovine leukosis (EBL), caused by BLV, although asymptomatic, leads to decreased production and economic losses. In humans, HTLV-1 was the first human retrovirus described in the 1980s. In this work, the similarities between cytomorphological changes in felines, cattle and humans affected by FeLV, BLV and HTLV-1, respectively, were analyzed. The bibliographic findings showed that the affected species addressed share the presence of atypical and/or reactive lymphocytes, smudge cells, immature cells and nuclear cell atypias in peripheral blood.