Case Report: Synovial sarcoma with diffuse myxoid stroma and complete absence of epithelial differentiation in the extremity - Report - MDSpire

Case Report: Synovial sarcoma with diffuse myxoid stroma and complete absence of epithelial differentiation in the extremity

  • By

  • Tomohiro Miyazaki

  • Naoki Oike

  • Takashi Ariizumi

  • Yudai Murayama

  • Akira Ogose

  • Hideaki Sugino

  • Mai Nakamura

  • Shuhei Kondo

  • Yusuke Tani

  • Hajime Umezu

  • Hiroyuki Kawashima

  • May 29, 2026

  • 0 min

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Clinical Report: Diffuse Myxoid Stroma in Synovial Sarcoma Lacking Epithelial Differentiation

Overview

This report details a rare case of synovial sarcoma presenting with diffuse myxoid stroma and absence of epithelial marker expression. The diagnosis was confirmed through molecular testing.

Background

Synovial sarcoma is a significant soft-tissue malignancy that accounts for 5-10% of adult sarcomas, typically characterized by the SS18–SSX fusion gene. Variants with myxoid stroma can mimic other sarcomas.

Data Highlights

No numerical data or trial data provided in the article.

Key Findings

  • A 61-year-old woman presented with a soft tissue tumor on the right thigh.
  • Imaging revealed a 55-mm mass with heterogeneous high signal intensity on T2-weighted MRI.
  • Core needle biopsy showed atypical spindle to round cells in a myxoid background.
  • Immunohistochemistry demonstrated negative cytokeratin and positive SOX9, raising suspicion for extraskeletal myxoid chondrosarcoma.
  • Molecular profiling confirmed the presence of the SS18–SSX1 fusion gene, establishing the diagnosis of synovial sarcoma.
  • The tumor exhibited a diffuse myxoid stroma and lacked epithelial marker expression throughout the disease course.

Clinical Implications

Clinicians should be aware of the potential for myxoid phenotypes in synovial sarcoma that may lack traditional epithelial markers.

Conclusion

The case illustrates a rare presentation of synovial sarcoma that complicates diagnosis.

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  4. Frontiers in Oncology, 2026 -- Case Report: Iliac perivascular myeloid sarcoma presenting with iliofemoral deep vein thrombosis and hydronephrosis
  5. IARC Publications Website - Soft Tissue and Bone Tumours
  6. Soft tissue and visceral sarcomas: ESMO–EURACAN–GENTURIS Clinical Practice Guidelines for diagnosis, treatment and follow-up☆ - ScienceDirect
  7. Safety and efficacy of Pazopanib in advanced soft tissue sarcoma: PALETTE (EORTC 62072) subgroup analyses - PMC
  8. IARC Publications Website - Soft Tissue and Bone Tumours
  9. Soft tissue and visceral sarcomas: ESMO–EURACAN–GENTURIS Clinical Practice Guidelines for diagnosis, treatment and follow-up☆ - ScienceDirect
  10. Safety and efficacy of Pazopanib in advanced soft tissue sarcoma: PALETTE (EORTC 62072) subgroup analyses - PMC

Original Source(s)

Case Report: Synovial sarcoma with diffuse myxoid stroma and complete absence of epithelial differentiation in the extremity

  • by Tomohiro Miyazaki, Naoki Oike, Takashi Ariizumi, Yudai Murayama, Akira Ogose, Hideaki Sugino, Mai Nakamura, Shuhei Kondo, Yusuke Tani, Hajime Umezu, Hiroyuki Kawashima

  • May 29, 2026

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