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Synovial sarcoma, histologically mimicking primitive neuroectodermal tumor/Ewing's sarcoma at distant sites
F Masui1, Y Matsuno, R Yokoyama
1Pathology Division, National Cancer Center Research Institute, Tokyo, Japan.
Japanese Journal of Clinical Oncology
|November 24, 1999
Summary
This case study details a synovial sarcoma (SS) that metastasized to bone and lungs, presenting as undifferentiated small round cell tumors. Genetic analysis confirmed these were metastatic SS, not a secondary primitive neuroectodermal tumor (PNET)/Ewing's sarcoma (ES).
Area of Science:
- Oncology
- Pathology
- Molecular Diagnostics
Background:
- Synovial sarcoma (SS) is a rare soft tissue sarcoma.
- Unusual presentations of SS, particularly with distant metastases exhibiting distinct histology, pose diagnostic challenges.
Observation:
- A patient with foot SS developed widespread bone and lung lesions during chemotherapy.
- Histology of metastases showed undifferentiated small round cells, unlike the primary biphasic SS.
- Immunohistochemistry revealed MIC2 protein expression in metastatic lesions.
Findings:
- Reverse transcription-polymerase chain reaction (RT-PCR) detected the SYT/SSX fusion transcript in both primary and metastatic tumors.
- The EWS/FLI1 transcript, characteristic of PNET/ES, was absent.
- These findings confirmed the metastatic nature of the bone and lung lesions originating from the primary SS.
Implications:
- Chimeric fusion transcript analysis is valuable for diagnosing poorly differentiated sarcomas.
- This technique aids in differentiating metastatic SS from other small round cell tumors like PNET/ES.
- Cytoplasmic MIC2 expression can occur in sarcomas beyond PNET/ES, requiring careful interpretation.