Eosinophilic granulated cells comprising a tumor in a Fischer rat

A systemic tumor developed in multiple organs, including spleen, bone marro w, lymph nodes, liver, ovaries, and thoracic and lumbar vertebrae, of a fem ale F344Du/Crj rat. The tumor was composed of round to indented mononuclear cells containing abundant large eosinophilic granules in the cytoplasm. Th e peripheral blood smear revealed that the large granules in the cytoplasm of the tumor cells were stained basophilic with Giemsa, suggesting a basoph il or mast cell origin. However, these granules did not show metachromasia with toluidine blue and were stained blue to dark blue with phosphotungstic acid hematoxylin. Cellular morphology and characteristics in the specific stains of tumor cells suggested the development of a tumor of globule leuko cytes in a F344Du/Crj rat.