Histiocytic sarcoma

Histiocytic sarcoma in the stomach of a 13-year-old Cocker Spaniel. Note the multiple ulcerated masses that deform the wall of the organ. These masses correspond to infiltration of the entire thickness of the gastric wall by round cells (neoplastic histiocytes). The tumour had already metastasized to the intestine, lymph nodes, spleen, liver and lung.