title: Spontaneous histiocytic sarcoma of the popliteal lymph node in a young sprague-dawley rat.
abstract: The present report describes a rare case of spontaneous primary histiocytic sarcoma of the popliteal lymph node in a 19-week-old female Sprague-Dawley (SD) rat. At necropsy, a 10 mm-diameter whitish nodule was found at the site of the femoral muscle in the right hindlimb. Histopathologically, the nodule comprised large pleomorphic histiocyte-like cells with abundant eosinophilic or foamy cytoplasm. Multinucleated giant cells, necrotic foci surrounded by palisading arrays of epithelioid histiocyte-like cells and phagocytosis of cell debris or erythrocytes by the neoplastic cells were occasionally observed. Invasion of the tumor cells into the surrounding adipose tissue was found focally, but there were no distal metastases. Immunohistochemically, the neoplastic cells were positive for vimentin, CD68 (ED1) and lysozyme. We concluded that this tumor occurred in the popliteal lymph node, considering the anatomical location of the lesion and the presence of the remnants of lymphoid tissue involved in the tumor.
authors.affiliation: Toxicology Research Laboratories, Central Pharmaceutical Research Institute, Japan Tobacco Inc., 23 Naganuki, Hadano, Kanagawa 257-0024, Japan.
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Kemmochi
authors.forename: Akemi
authors.initials: A
authors.lastname: Takahashi
authors.forename: Katsuhiro
authors.initials: K
authors.lastname: Miyajima
authors.forename: Yuzo
authors.initials: Y
authors.lastname: Yasui
authors.forename: Gimpei
authors.initials: G
authors.lastname: Tanoue
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Shoda
authors.forename: Kochi
authors.initials: K
authors.lastname: Kakimoto