A 10-year-old spayed female Rottweiler presented to the Cornell University Hospital for Animals Oncology Service on May 22, 2006 for regurgitation, coughing, left-sided Horner's Syndrome, hind limb ataxia, thrombocytopenia, and anemia. Diagnostic imaging revealed megaesophagus and multiple hypoechoic splenic masses. Cytologic analysis of aspirate samples from the splenic masses and bone marrow was consistent with metastatic histiocytic sarcoma (HS). Euthanasia was elected due to poor prognosis, and a necropsy was performed, confirming the diagnosis of HS.
Histiocytic sarcoma is a rare and/or commonly misdiagnosed disease with a breed predisposition in Bernese Mountain Dogs, Rottweilers, and retrievers. It is a neoplasm of myeloid dendritic antigen-presenting cells (APCs) that stain positive for CD18, BLA-36, and MAC387. The two forms of histiocytic sarcoma are localized and disseminated, differentiated by the primary tumor site and the sites of secondary spread. HS has a poor prognosis.