Evaluation of buffy coat smears for circulating mast cells in healthy cats and ill cats without mast cell tumor-related disease.

To examine buffy coat smears for circulating mast cells in clinically normal cats and cats with illnesses unrelated to mast cell tumors and identify whether conditions other than mast cell tumors are associated with mastocytemia in cats. Prospective study. 40 clinically normal cats and 40 cats with diseases unrelated to mast cell tumors (all cats were client owned). A blood sample for a CBC, serum biochemical analyses, and buffy coat evaluation was obtained from each cat. Ill cats underwent other testing on the basis of their disease process. No mast cells were detected in any sample. Eosinophilia was evident in 11 (27.5%) and 12 (30%) clinically normal and ill cats, respectively. Basophilia was identified in 4 (10%) and 8 (20%) clinically normal and ill cats, respectively. Eight of the 40 (20%) ill cats had neutrophilia. Circulating mast cells were not identified in clinically normal cats or ill cats without mast cell tumor-related disease. Ill cats did have conditions that caused eosinophilia, basophilia, or neutrophilia. The absence of mast cells in buffy coats obtained from clinically normal and ill cats lends support to the current practice of buffy coat evaluation for tumor staging and follow-up examinations in cats with mast cell tumors. Further studies of buffy coat analysis in cats with different forms of mast cell tumors are indicated to specifically elucidate the test's prognostic value for those patients.