Pathological and Immunohistochemical Findings of Disseminated Histiocytic Sarcoma in a Sugar Glider (Petaurus breviceps).

A 6-year-old intact female sugar glider (Petaurus breviceps) had a swelling at the pouch region and died 8 days after presentation. At necropsy, the urinary bladder and abdominal lymph nodes were enlarged and a mass was located in the pericloacal region. Tumour infiltration was also observed in the medial iliac lymph nodes, liver, spleen, small intestine, uterus and left ovary. Histopathologically, the tumours were composed of pleomorphic histiocytes that had round or bizarre nuclei and abundant pale eosinophilic cytoplasm. Immunohistochemically, tumour cells were positive for ionized calcium-binding adaptor molecule 1 and human leukocyte antigen and negative for CD3, B lymphocyte antigen 36 and cytokeratin. Histopathological and immunohistochemical examinations confirmed a diagnosis of disseminated histiocytic sarcoma. This neoplasm has not been previously reported in a sugar glider.