title: Hepatoid tenosynovial giant cell tumor - a rare morphologic variant case report.
abstract: We report a morphologically rare type of tenosynovial giant cell tumor (TSGCT), localized type, occurring in a 49-year-old man. Imaging examination revealed multiple nodular lesions around the right knee joint. The largest one extended to both intra- and extra-osseous region of the right distal femur. Histologically, the tumor consisted of epithelioid mononuclear cells and they looked like to have abundant eosinophilic cytoplasm reminiscent of hepatic tissues. In some areas, however, typical histologic features of TSGCT were observed. Electron microscopy revealed that the eosinophilic cytoplasm-like substance was intercellular fibrinous material surrounding the mononuclear tumor cells. Immunohistochemically, mononuclear tumor cells and multinucleate giant cells were positive for CD68 (Kp1) and some of the mononuclear tumor cells were also positive for desmin. Finally, we made the diagnosis of hepatoid TSGCT.
authors.affiliation: Division of Pathology, The Cancer Institute, Japanese Foundation for Cancer Research, Tokyo, Japan.
authors.forename: Toyoki
authors.initials: T
authors.lastname: Yoshimoto
authors.affiliation: Division of Pathology, The Cancer Institute, Japanese Foundation for Cancer Research, Tokyo, Japan. Electronic address: noriko.motoi@jfcr.or.jp.
authors.forename: Noriko
authors.initials: N
authors.lastname: Motoi
authors.affiliation: Division of Pathology, The Cancer Institute, Japanese Foundation for Cancer Research, Tokyo, Japan.
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Kanda
authors.affiliation: Department of Orthopedic Surgery, The Cancer Institute Hospital of JFCR, Japanese Foundation for Cancer Research, Tokyo, Japan.
authors.forename: Taisuke
authors.initials: T
authors.lastname: Tanizawa
authors.affiliation: Department of Orthopedic Surgery, The Cancer Institute Hospital of JFCR, Japanese Foundation for Cancer Research, Tokyo, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Shimoji
authors.affiliation: Department of Orthopedic Surgery, The Cancer Institute Hospital of JFCR, Japanese Foundation for Cancer Research, Tokyo, Japan.
authors.forename: Seiichi
authors.initials: S
authors.lastname: Matsumoto
authors.affiliation: FML Laboratory, Tokyo, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Mukai
authors.affiliation: Division of Pathology, The Cancer Institute, Japanese Foundation for Cancer Research, Tokyo, Japan.
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Ishikawa
authors.affiliation: Division of Pathology, The Cancer Institute, Japanese Foundation for Cancer Research, Tokyo, Japan; Department of Pathology, Kawakita General Hospital, Tokyo, Japan.
authors.forename: Rikuo
authors.initials: R
authors.lastname: Machinami
mesh_terms: D015703:Antigens, CD / Q000378:metabolism; D015214:Antigens, Differentiation, Myelomonocytic / Q000378:metabolism; D001706:Biopsy / Q000379:methods; D005870:Giant Cell Tumors / Q000175:diagnosis / Q000473:pathology*; D006801:Humans; D008297:Male; D008854:Microscopy, Electron / Q000379:methods; D008875:Middle Aged; D012983:Soft Tissue Neoplasms / Q000175:diagnosis / Q000473:pathology*; D013583:Synovial Membrane / Q000648:ultrastructure*; D000097382:CD68 Molecule
chemical_list: D015703:Antigens, CD; D015214:Antigens, Differentiation, Myelomonocytic; C067980:CD68 antigen, human; D000097382:CD68 Molecule
keywords: Hepatoid histological features; Involvement of bone; Tenosynovial giant cell tumor