Objective—To determine whether the extent of disease in dogs with lymphoma can be assessed via flow cytometry and to evaluate the suitability of fine-needle aspirates from the liver and spleen of dogs for flow cytometric examination.
Animals—44 dogs with multicentric B-cell (n = 35) or T-cell lymphoma (9) and 5 healthy control dogs.
Procedures—Peripheral blood and bone marrow samples and fine-needle aspirates of lymph node, liver, and spleen were examined via flow cytometry. Logarithmically transformed T-cell–to–B-cell percentage ratio (log[T:B]) values were calculated. Thresholds defined by use of log(T:B) values of samples from control dogs were used to determine extranodal lymphoma involvement in lymphoma-affected dogs; results were compared with cytologic findings.
Results—12 of 245 (5%) samples (9 liver, 1 spleen, and 2 bone marrow) had insufficient cellularity for flow cytometric evaluation. Mean log(T:B) values of samples from dogs with B-cell lymphoma were significantly lower than those of samples from the same site in dogs with T-cell lymphoma and in control dogs. In dogs with T-cell lymphoma, the log(T:B) of lymph node, bone marrow, and spleen samples was significantly higher than in control dogs. Of 165 samples assessed for extranodal lymphoma involvement, 116 (70%) tested positive via flow cytometric analysis; results agreed with cytologic findings in 133 of 161 (83%) samples evaluated via both methods.
Conclusions and Clinical Relevance—Results suggested that flow cytometry may aid in detection of extranodal lymphoma involvement in dogs, but further research is needed. Most fine-needle aspirates of liver and spleen were suitable for flow cytometric evaluation.