Cutaneous B cell lymphoma in a Mongolian gerbil (Meriones unguiculatus)

A mass was noticed on the right mandible of an aged male Mongolian gerbil. Because of rapid enlargement of the mass, the animal was euthanized and sub mitted for pathology. The mass was firm, pink in color, 15 min in diameter, and tightly adherent to adjacent tissues. Staining with hematoxylin and eo sin revealed that the mass was a lymphoid tumor. Neoplastic cells had a lar ge, round, dense nuclei and little cytoplasm. The tumor contained numerous mitotic figures. Immunohistochemical stains showed that the neoplastic cell s expressed CD19 and IgM but lacked CD3 and CD5. Flow cytometric analysis s howed that the neoplastic cells were positive for B220, IgG, and CD40. We c oncluded that the tumor was a primary cutaneous B cell lymphoma. In additio n, the antibodies we used for the present diagnosis were anti-mouse reagent s; therefore, they also were useful for subtyping gerbil lymphoid cells.