Factors correlating with circulating T-zone-like cells of undetermined significance (TZUS) in dogs resident in Italy

T-zone-like cells of undetermined significance (TZUS) share the same phenotypic pattern (CD45-CD5+) with Tzone lymphoma cells and were first described a few years ago in the peripheral blood (PB) of healthy aged American Golden retrievers (GR). History of bladder and eye disease increased the odd of circulating TZUS in the American GR population. Since differences among dogs may exist according to the geographical region of origin, herein we screened 489 PB samples to assess potential factors predisposing to the presence of circulating TZUS in dogs living in Italy. Overall, TZUS were found in 174 (35.6 %) samples. Among 83 clinical variables, significant associations emerged with sex, age, diagnosis of neoplasia, history of neoplasia, history of infectious or parasitic disease, history of osteoarticular disease, presence of traumatic lesions or foreign bodies, and lymphocytes count. Only age and history of neoplasia retained significance at multivariate analysis (p=0.019 and p=0.036, respectively). Thus, older age and history of neoplasia are the main factors associated with circulating TZUS in Italian dogs. Future studies should focus on elucidating the biological role of TZUS and determining reproducible criteria for their identification, distinguishing them from infiltrating TZL.