Cytohistophatology of dermal mass from the axillary of the dog. Representative photomicrographs of mass cell tumuor of Patnaik grade. (A and B) grade III. High-grade mast cell tumour was characterized by highly pleomorphic tumour cells with a high mitotic index, anisokaryosis and infiltration of the surrounding dermis and subcutis. Haematoxylin and eosin stain. Bar, 50 μm. the smears show n were prepared at the initial presentation and stained with Wrigth-Giemsa solution. Histopathologically, The presence of eosinophils and the observation, at high magnification, of cells with cytoplasmic metachromatic granules and also, neoplastic cells often exhibited an aggressive behavior, high cellularity, cellular pleomorphism, and various morphologic patterns. Eosinophils are present at the periphery of the mass (Figure 1C and D, H&E, 400x).