Cytomorphology of Canine Cutaneous Round Cell Tumours: Differentiating Histiocytoma from Mast Cell Tumour– A Case Report

Abstract

Background: Cutaneous round cell tumours are among the most common skin neoplasms in dogs, with histiocytoma and mast cell tumours frequently encountered in clinical practice. Rapid and accurate diagnosis is essential for appropriate therapeutic management and prognosis. Case Presentation: Two dogs, a Labrador and a Pug, were presented at the Department of Veterinary Surgery and Radiology, Institute of Veterinary Sciences and Animal Husbandry, SOA (Deemed to be University), Bhubaneswar, Odisha, India, with a history of nodular growth on the hind limb and skin. Fine needle aspiration biopsy (FNAB) was performed, and Giemsa-stained smears were examined. Cytological evaluation of one case revealed features consistent with histiocytoma, characterized by round to oval neoplastic cells with indented nuclei and abundant pale blue cytoplasm arranged in a discrete pattern. The second case showed typical features of mast cell tumour, including round neoplastic cells with distinct metachromatic intracytoplasmic granules. Management and Outcome: Based on the cytological diagnosis, appropriate therapeutic management was initiated. Both cases responded well to treatment and showed a favourable clinical outcome without immediate complications. Conclusion: This case report highlights the importance of FNAB cytology as a rapid, minimally invasive, and reliable diagnostic tool for differentiating cutaneous round cell tumours in dogs, thereby facilitating timely clinical intervention and improved prognosis.