Cutaneous mast cell tumor (Mastocytoma): cyto- histopathological and haematological investigations

Abstract

Cutaneous mast cell tumours (MCTs) are the most common skin tumours in dogs. Due to the prevalence of canine MCTs and the variable biologic behavior of this disease, accurate prognostication and a thorough understanding of MCT biology are critical for the treatment of this disease. A cytologic diagnosis of mast cell tumor with evidence of prior hemorrhage was made, and the masses were surgically removed. Cytological evaluation of fine-needle aspirates from the cutaneous mass from the axillary comprised many well-differentiated, highly granulated mast cells with moderate numbers of eosinophils. Nuclei were varied in size and shape with high nuclear'to'cytoplasmic ratio, prominent nucleoli, marked atypical and mitotic figures. Microscopically, mass consisted of sheets of neoplastic round cells that formed nonencapsulated nodules in the dermis and infiltrated into the adjacent dermal collagen, and also there was diffuse subcutis invasion of round to pleomorphic tumor cells. Tumor cells had moderate to abundant cytoplasm, round to ovoid nuclei with scattered chromatin, and mitotic figures. In this tumor, cytoplasmic granules showed atypical metachromasia. In addition, eosinophils were scattered among the mast cells at the periphery of the nodules. The presence of eosinophils and the observation, at high magnification, of cells with cytoplasmic metachromatic granules. Invasion of the deep subcutaneous fat or cutaneous muscles were a common feature of grade III tumour. Finally, a diagnosis of grade III cutaneous mast cell tumor was made.

Virtual slides: The virtual slide(s) of this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/4755249151157024.

Figure 1

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).

Figure 2

Macroscopical examination of a cutaneous cell tumor in a black terrier. The mass spreading into subcutis is of proximal right front leg.