29 Nov Histiocytic Sarcoma
Aspirate from an abdominal mass of a 5-year-old spayed female Shetland Sheepdog. The presenting complaint was anorexia and vomiting for 1.5 weeks. An abdominal radiograph suggested a possible mid-abdominal mass. On ultrasound, a mixed echogenicity liver mass and an extremely large mixed echogenicity abdominal mass of unknown origin was found. Both lesions were aspirated; an image of the abdominal mass cytology is below.
The image consists of a moderate amount of peripheral blood that surrounds numerous large malignant histiocytes. These cells have an abundant amount of gray cytoplasm that is frequently vacuolated, and a round to irregularly shaped nucleus with coarsely stippled chromatin and occasional visible nucleoli. Anisokaryosis is marked; anisocytosis is moderate. Binucleation is also apparent. In other fields (not pictured), multinucleation is frequently noted, and leukophagocytosis is also occasionally found. The definitive cytologic diagnosis was histiocytic sarcoma. Cytology of the liver mass was identical to this lesion, consistent with a metastatic process.