Splenic marginal zone lymphoma in a European harvest mouse (Micromys minutus)

A splenic marginal zone lymphoma was diagnosed in a female European harvest mouse (Micromys minutus) that presented clinically with poor body condition and abdominal swelling. On palpation, a mass in the cranial abdomen was identified. The owner elected euthanasia. Necropsy revealed a markedly enlarged spleen, which was uniformly pale red. Histological examination of the spleen revealed monomorphic sheets expanding from the marginal zone composed of large polygonal to oval cells containing abundant finely granular eosinophilic cytoplasm. No abnormalities were noted in any other organs. Immunohistochemical evaluation of the tumor cells demonstrated positive staining for CD45R and IgM and negative staining for CD4, CD8 and IgD. The diagnosis of splenic marginal zone lymphoma was based on the anatomical location, the lack of involvement of other organs and the histological and immunohistochemical findings. © Springer-Verlag London Limited 2006.