Abdominal Distension in an Aged Female Mouse (Mus musculus)

Gross examination of the animal. (A) There was abdominal effusion and whole-body subcutaneous edema. (B) Both kidneys (indicated by arrows) were enlarged and yellow to white in color. The asterisk marks a mass at the mesentery. The spleen was enlarged.

Cytology of impression smear of caudal mesenteric lymph node. (A) Numerous neoplastic cells were observed with round cell morphology, and with vacuolated cytoplasm. (B) Another view of the cytology slide showed clusters of neoplastic round cells with the presence of a binucleated cell. Scale bars, 20 µm.

Histopathology of histiocytic sarcoma in visceral organs. (A) The ovary was effaced by neoplastic cells. Scale bar, 2 mm. (B) Higher magnification of the histiocytic sarcoma from (A), showing sheets of pleomorphic neoplastic cells with abundant cytoplasm. Scale bar, 100 µm. (C) The kidney was largely infiltrated by the neoplastic cells, and multiple renal tubules contained bright magenta hyaline droplets. Scale bar, 100 µm. (D) Liver had tumor infiltration predominantly locating at the perivascular and periportal areas. Scale bar, 100 µm. (E) The heart had a tumor mass at the endocardium. Scale bar, 200 µm. (F) The pancreatic lymph node was enlarged and effaced by the tumor. Scale bar, 2 mm.

Immunohistochemical staining of the tumor mass. (A) Tumor cells in the ovary showed diffusely positive, membranous staining of F4/80. (B) Tumor cells were negative to CD45R-B200. Scale bars, 50 µm.