Histomorphology and cytology of cutaneous mastocytoma in a dog

A case of mastocytoma was observed in a seven-year-old male mongrel dog. The dog was brought to the small animal clinic with the history of anorexia, lethargy and weight loss over a period of one month. Clinical examination of the dog revealed no abnormality except a growth on the right perineum. Haematology parameters were normal except leucocytosis due to eosinophilia and basophilia. No changes were observed in serum biochemical parameters. Impression smears from the growth revealed sheets of mast cells with very high pigmentation. Neoplastic cells were well differentiated and pleomorphic with indistinct cell boundaries. Nuclei were round to oval and often irregular in shape. Histopathology of the growth revealed the features of mastocytoma consisting high cellularity, marked cellular pleomorphism, anisocytosis and anisokaryosis. Marked infiltration of eosinophils was noticed throughout the tumour. Clinico-pathology, cytology and histopathology findings were consistent for diagnosis of canine mastocytoma.