Epidermotropic Lymphoma (Mycosis Fungoides) in an ICR Mouse.

A case of epidermotropic lymphoma with systemic spread into lymph nodes and visceral organs was observed in a 7- to 8-month-old, female ICR mouse. The mouse developed progressive and generalized alopecia and lymphadenopathy of several weeks' duration. The affected skin was markedly and diffusely thickened, with multiple serous to hemorrhagic crusts, ulcerated plaques, and raised nodules. Microscopically, random and/or perivascular infiltration of pleomorphic lymphoid cells was present in the skin, lymph nodes, thymus, spleen, lungs, and liver. On cytologic examination, the lymphoid cells were similar in all affected tissues, and had hyperchromatic and irregularly oval, cleaved, and occasionally convoluted nuclei, approximately 6 to 9 mm in diameter. On immunohistochemical examination, most infiltrating cells were labeled with anti-CD3 (panT cell) antibody. A smaller proportion of the cells (, 5%) were labeled with anti-CD79a (panB cell) antibody.