author(s)
Lalrinkima, M Thangapandiyan, S Hemalatha and GV Sudhakar Rao

abstract
A 3 year old male German Shepherd was presented with a history of swelling on the submandibular region and was brought to Madras Veterinary College, Chennai-600 007 for postmortem examination. Necropsy examination revealed a 10-15 cm white lobulated mass on the right side of subcutis of the submandibular region. Internal examination revealed nodules on cortex of both the kidneys. Severe ulcerative lesions was seen in the stomach and duodenum. Cytologically, discrete round cells pleomorphic, with abundant cytoplasm and ovoid and indented nuclei. Histopathological examination revealed diffuse infiltration of large round to pleomorphic cells with abundant eosinophilic cytoplasm with ovoid to bean shaped nuclei with distinct cell margins. The cells were arranged as loose sheets with minimal fibrous stroma. Nuclei were hyperchromatic with prominent multiple nucleoli. Scanty mitoses was observed. For differential diagnosis of round cell tumors mast cells were ruled out by toludine blue staining which was found to be negative. Immunohistochemistry for mast cell tumor was carried out for Ckit and was found to be negative. Specific expression of immunohistochemical markers for histiocytic cell type CD 18 showed diffuse intense cytoplasmic positivity for the markers. Both dermal and metastatic areas in the kidney expressed these specific histiocytic markers.