title: Ossifying synovial sarcoma.
abstract: Although intralesional calcification is a common finding of synovial sarcoma, ossification is an unusual phenomenon in such a soft tissue sarcoma. Here we report a case of ossifying synovial sarcoma arising in the back of a young adult man. Microscopically, the tumor was composed of spindle or oval cells together with foci of atypical polygonal cells in small nests or cord-like structures, displaying an epithelial appearance. In addition, extensive osteoid or woven bone formation was present in the tumor, resembling extraskeletal osteosarcoma. However, an SS18-SSX1 fusion gene transcript was detected by reverse transcription-polymerase chain reaction, supporting the diagnosis of biphasic synovial sarcoma. The osteogenic phenotype of the tumor cells was further demonstrated by an intense immunohistochemical expression of Runx2, a key transcription factor involved in the regulation of osteoblastic differentiation. The current case suggests the diagnostic utility of the molecular detection of a tumor type-specific fusion gene and expands the phenotypic plasticity of the soft tissue sarcoma of uncertain differentiation.
authors.affiliation: Department of Pathology and Oncology, School of Medicine, University of Occupational and Environmental Health, 1-1 Iseigaoka, Yahatanishi-ku, Kitakyushu 807-8555, Japan. hisaoka@med.uoeh-u.ac.jp
authors.forename: Masanori
authors.initials: M
authors.lastname: Hisaoka
authors.forename: Atsuji
authors.initials: A
authors.lastname: Matsuyama
authors.forename: Shohei
authors.initials: S
authors.lastname: Shimajiri
authors.forename: Jun
authors.initials: J
authors.lastname: Akiba
authors.forename: Hironori
authors.initials: H
authors.lastname: Kusano
authors.forename: Koji
authors.initials: K
authors.lastname: Hiraoka
authors.forename: Takanori
authors.initials: T
authors.lastname: Shoda
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Hashimoto
mesh_terms: D000328:Adult; D001483:Base Sequence; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D015514:Oncogene Proteins, Fusion; D009999:Ossification, Heterotopic / Q000235:genetics* / Q000473:pathology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013584:Sarcoma, Synovial / Q000235:genetics* / Q000378:metabolism / Q000473:pathology*; D012983:Soft Tissue Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology*; D014057:Tomography, X-Ray Computed
chemical_list: D015514:Oncogene Proteins, Fusion; C116512:SYT-SSX fusion protein