Different cytogenetic findings in two clinically similar leukaemic dogs

A 4-month-old German Shepherd puppy and a 7-year-old Boxer dog, in which a clinical diagnosis of acute lymphoblastic leukaemia had been made, were investigated cytogenetically. In the puppy a diploid karyotype was found, but the malignant clone in the Boxer was characterized by an extra metacentric chromosome, apparently formed as the result of a Robertsonian translocation of two chromosomes 1. These findings are discussed against the background of similar cases reported in the literature. Possibly, different types of acute canine leukaemic disease, occurring at different ages, can be distinguished by cytogenetic evaluation.