Chemotherapy in a dog with neutropenia and marginal zone lymphoma.

A 12-year-old Beagle dog with generalized lymphadenopathy and persistent neutropenia was diagnosed with advanced marginal zone lymphoma based on cytology, histopathology, and polymerase chain reaction for antigen receptor rearrangement analysis. Bone marrow examination revealed hypocellularity predominantly affecting the myeloid lineage, while normal morphology and maturation were preserved across hematopoietic lineages, with no evidence of myelophthisis or fibrosis. Chemotherapy was initiated using a modified and dose-reduced multi-agent protocol, followed by L-asparaginase and nimustine; full-dose chemotherapy was also subsequently tolerated without serious adverse events. Two complete remissions were achieved during the treatment course. Normalization of the neutrophil count during tumor progression was presumed to reflect increased neutrophil demand associated with disease progression, indicating that compensatory hematopoietic capacity was preserved. This case illustrates that, in dogs with persistent neutropenia and myeloid hypoplasia, chemotherapy may be considered when bone marrow evaluation confirms preserved hematopoietic maturation and careful monitoring is performed.