Among the hematopoietic neoplasms, leukemias are caused by myeloid or lymphoid cells in the bone marrow, which can either be acute with an unfavorable prognosis and mostly affect cats that tested positive for feline viral leukemia (FeLV) or chronic in older cats that have a poor prognosis. Leukemias have several classifications in which the differentiation depends on complementary tests, such as blood profile, myelogram, cytology. and flow cytometry, which help determine the best treatment for the animal.