Ossifying synovial sarcoma.
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.
Hisaoka
Masanori
M
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
Matsuyama
Atsuji
A
Shimajiri
Shohei
S
Akiba
Jun
J
Kusano
Hironori
H
Hiraoka
Koji
K
Shoda
Takanori
T
Hashimoto
Hiroshi
H
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
D015514:Oncogene Proteins, Fusion; C116512:SYT-SSX fusion protein