Interestingly, there is one arena in which median survival times in osteosarcoma have been extended - patients who develop infections after limb-spare surgery have been observed to double their median survival time. Lascelles et al. noted that infected dogs were half as likely to die, half as likely to develop metastasis, and these survival effects were due to a delay in metastasis rather than control of local tumor recurrence.8 A similar phenomenon of increased survival in infected human osteosarcoma patients has been observed. Jeys et al.reported that the 10-year survival rate in humans was significantly better in infected limb-spares: 84.5% in the infected patients versus 62.2% in the non-infected patients.9 An upregulation of antitumor immunity has been postulated to be potentially responsible for the favorable survivals in the face of an infection in dogs and humans. Characterization of the phenotype and function of circulating canine and human monocytes in normal subjects, and in osteosarcoma subjects with and without an infection will be crucial in furthering their understanding of how these cells are involved in the pathogenesis and potential suppression of osteosarcoma.