Cytological diagnosis of canine cutaneous mast cell tumour with nodal metastasis

A thirteen year old male mongrel dog was presented at Sanchu animal hospital, Palavakkam, Chennai for treatment of two months old wound infected with maggots in the interdigital space of the left forelimb. Physical examination of the animal revealed the presence of a large ulcerated wound infested with maggots and a foul smelling discharge from the interdigital space between 3rd and 4th digit of the left forelimb. In addition, left prescapular lymphnode showed marked enlargement. Radiological examination of the affected limb revealed complete osteolytic lesions in the distal phalanges (P2 and P3) of the 4th digit, while no abnormalities were noticed in thorax and abdomen. After five days of treatment with ivermectin and antibiotics, maggots disappeared completely leaving an ulcerated nodule with soft consistency and measuring 4 cm in diameter. Impression smears from the site showed presence of numerous discrete round cells having moderate amounts of pale basophilic cytoplasm with varying numbers of characteristic metachromatic granules, suggestive of mast cell tumour (MCT). Fine needle aspirates from enlarged lymphnode also showed clusters of neoplastic cells comprised of mast cells along with numerous neutrophils, confirming its metastasis. Based on the laboratory findings, diagnosis was confirmed as cutaneous MCT with nodal metastasis (stage II). Thus, the present paper reports the cytological findings of cutaneous MCT with lymph node metastasis in a mongrel dog.