Results suggested that doxorubicin chemotherapy may play a role in extending the disease-free interval in cats undergoing radiotherapy for treatment of incompletely excised soft tissue sarcomas.

Bone marrow aspiration for routine staging of canine cutaneous mast cell tumour is not consistently performed, and the overall incidence of bone marrow infiltration and predictive value of the complete blood count (CBC) is unknown. This study evaluated a series of 157 dogs presented for cutaneous mast cell tumours in which a CBC and bone marrow aspiration were performed. The incidence of bone marrow infiltration at initial staging was low at 2.8%, and 4.5% overall. Factors significantly associated with bone marrow infiltration included increased age, leucocytosis, anaemia, neutrophilia, monocytosis, eosinophilia, thrombocytopenia, being purebred and staging at the time of recurrent or progressive disease. Our study suggests that a bone marrow sample is not indicated for routine staging but maybe indicated for those dogs with mast cell tumours having either an abnormal haemogram (neutrophilia, monocytosis, eosinophilia, basophilia, anaemia and thrombocytopenia) or presenting for tumour regrowth, progression or new occurrence.

Background Tumors have heterogeneous properties, which could be explained by the existence of hierarchically and biologically distinct tumor cells such as tumor-initiating cells (TICs). This model is clinically important, as TICs are promising targets for cancer therapies. However, TICs in spontaneous B-cell lymphoma have not been conclusively identified. Hypothesis/Objectives Tumor cells with a progenitor phenotype exist in B-cell lymphoma, reflecting a hierarchical organization. Animals Twenty-eight client-owned dogs with previously untreated B-cell lymphoma and six healthy dogs. Methods This was a prospective study. Flow cytometry was used to identify lymphoid progenitor cells (LPCs) that co-expressed hematopoietic progenitor antigens CD34, CD117 (KIT), and CD133, with lymphoid differentiation markers CD21 and/or CD22 in B-cell lymphoma. The polymerase chain reaction for antigen receptor rearrangements was used to analyze clonality and relatedness of tumor populations. A xenograft model using NOD/SCID/IL-2Rγ−/− mice was adapted to expand and serially transplant primary canine B-cell lymphoma. Results LPCs were significantly expanded in lymph node samples from 28 dogs with B-cell lymphoma compared to six healthy dogs (p=0.0022). LPCs contained a clonal antigen receptor gene rearrangement identical to that of the bulk of tumor cells. Canine B-cell lymphoma xenografts in recipient mice that maintained LPCs in the tumors were recurrently observed. Conclusions and clinical importance These results suggest the presence of a hierarchy of tumor cells in canine B-cell lymphoma as has been demonstrated in other cancers. These findings have the potential to impact not only the understanding of lymphoma pathogenesis but also the development of lymphoma therapies by providing novel targets for therapy.

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