Synovial sarcoma of bone: Sarcoma typically of soft tissues presenting as a primary bone tumor

Abstract

Synovial sarcoma typically presents as periarticular soft tissue mass in adolescent and young adult patients. Very rarely, soft tissue sarcomas may arise primarily within bone posing a significant diagnostic challenge as primary osseous malignancies such as osteosarcoma and metastatic disease are much more common. While tissue sampling with immunohistochemical and genetic testing are required for definitive diagnosis, radiologists and orthopedic oncologists should consider alternate etiologies when typical imaging features of more common bone tumors are not identified. As an example, we present a 33-year-old male referred with a pathologic hip fracture proven to represent primary synovial sarcoma of bone.

Keywords: Primary bone tumor; Synovial sarcoma.

Fig. 1

Coronal T1-weighted SE and fat-suppressed T2-weighted TSE MR images demonstrate a T1-hypointense, T2-hyperintense heterogeneous proximal femoral mass with medial cortical destruction, and extra-osseous extension of disease consistent with an aggressive bone tumor. MR, magnetic resonance; SE, spin echo; TSE, turbo spine echo.

Fig. 2

AP radiograph of the right hip demonstrates a geographic, but ill-defined osteolytic lesion without mineralization involving the medial femoral neck and lesser trochanter with a radio-dense soft tissue mass.

Fig. 3

Unenhanced axial chest CT demonstrates multiple bilateral noncalcified pulmonary nodules consistent with metastatic disease. CT, computed tomography.

Fig. 4

Histopathology and immunohistochemical staining of synovial sarcoma. (A) Spindled cells of similar appearance with hyperchromatic nuclei and sparse cytoplasm exhibiting a “blue” appearance with scant stromal collagen (20x H&E). (B) Strong positive staining for CKAE1/3CAM. (C) Weakly positive staining for CK7. (D) Weakly positive staining for CD99. (E) Positive staining for Bcl-2. H&E, hematoxylin and eosin. (Color version of figure is available online.)