%0 Journal Article %T Spontaneous pancreatic undifferentiated pleomorphic sarcoma in a laboratory rat: A case report. %A Ypsilantis P %A Meditskou S %A Lambropoulou M %A Papamitsou T %A Simopoulos C %J Animal Model Exp Med %V 2 %N 3 %D Sep 2019 %M 31773099 暂无%R 10.1002/ame2.12078 %X We present a case of spontaneous undifferentiated/unclassified sarcoma, of a pleomorphic subtype formerly known as malignant fibrous histiocytoma (UPS/MFH), arising from the pancreas of a laboratory rat. The mass was excised after laparotomy from a 6-month-old female laboratory Wistar rat. It presented a giant multilobulated mass of irregular shape, which had arisen from the pancreas and occupied almost the entire peritoneal cavity. Histologically the tumor was characterized by a highly variable morphological pattern, with frequent transitions from storiform to pleomorphic areas. An extensive immunohistochemical examination revealed no specific lines of differentiation. Immunohistochemical positivity was observed only to MIB-1 (high Ki-67 proliferation index), vimentin and CD68 antibodies. The diagnosis was compatible with UPS/MFH. To the best of our knowledge, the present case is the first report of a spontaneous primary UPS/MFH arising from the pancreas of a laboratory rat.