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Peer-reviewedCC BYFrontiers in medicine

Primary extraskeletal osteosarcoma of the retroperitoneum: a case report.

  • Xiangxiang Ren1
  • Tianhao Xie1
  • Linqian Li2
  • Xiaoshi Jin1
  • Meng Zhang3
  1. 1Department of General Surgery, Affiliated Hospital of Hebei University, Baoding, China.
  2. 2Basic Research Key Laboratory of General Surgery for Digital Medicine, Affiliated Hospital of Hebei University, Baoding, China.
  3. 3Department of Dermatology, Affiliated Hospital of Hebei University, Baoding, China.
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Abstract

Extraskeletal osteosarcoma arising in the retroperitoneum is exceedingly rare, and its osteoid-producing histology closely mimics dedifferentiated liposarcoma. A 33-year-old woman presented with a 1-month history of progressive abdominal distension. Imaging revealed a 15 cm right retroperitoneal mass with punctate calcifications, no macroscopic fat, and no bone attachment. The mass was resected completely en bloc with negative microscopic margins (R0). Sections showed a high-grade sarcoma weaving through lace-like osteoid. MDM2 immunohistochemistry was negative and fluorescence in situ hybridization (FISH) detected no MDM2 amplification; CDK4 immunostaining and CDK4 FISH were likewise negative. No well-differentiated liposarcoma component was found on gross or microscopic examination, and together these findings ruled out 12q13-15 amplification. The final diagnosis was primary, high-grade extraskeletal osteosarcoma of the retroperitoneum. The patient received adjuvant MAP chemotherapy (methotrexate, doxorubicin, cisplatin) and at 25 months after surgery remains free of recurrence or metastasis; surveillance imaging will continue for at least 10 years. Any osteoid-producing retroperitoneal sarcoma without a well-differentiated liposarcoma component should undergo MDM2 amplification testing, and ideally CDK4 testing, because the two diagnoses are managed differently.

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Cite

BibTeXRIS
BibTeX
@article{ren2026primary,
  title = {{Primary extraskeletal osteosarcoma of the retroperitoneum: a case report.}},
  author = {Xiangxiang Ren and Tianhao Xie and Linqian Li and Xiaoshi Jin and Meng Zhang},
  journal = {Frontiers in medicine},
  year = {2026},
  month = oct,
  doi = {10.3389/fmed.2026.1921181},
  url = {https://europepmc.org/article/MED/42923544},
  note = {CC BY},
}
RIS
TY  - JOUR
TI  - Primary extraskeletal osteosarcoma of the retroperitoneum: a case report.
AU  - Xiangxiang Ren
AU  - Tianhao Xie
AU  - Linqian Li
AU  - Xiaoshi Jin
AU  - Meng Zhang
PY  - 2026
DA  - 2026/10/08
JO  - Frontiers in medicine
DO  - 10.3389/fmed.2026.1921181
UR  - https://europepmc.org/article/MED/42923544
AB  - Extraskeletal osteosarcoma arising in the retroperitoneum is exceedingly rare, and its osteoid-producing histology closely mimics dedifferentiated liposarcoma. A 33-year-old woman presented with a 1-month history of progressive abdominal distension. Imaging revealed a 15 cm right retroperitoneal mass with punctate calcifications, no macroscopic fat, and no bone attachment. The mass was resected completely en bloc with negative microscopic margins (R0). Sections showed a high-grade sarcoma weaving through lace-like osteoid. MDM2 immunohistochemistry was negative and fluorescence in situ hybridization (FISH) detected no MDM2 amplification; CDK4 immunostaining and CDK4 FISH were likewise negative. No well-differentiated liposarcoma component was found on gross or microscopic examination, and together these findings ruled out 12q13-15 amplification. The final diagnosis was primary, high-grade extraskeletal osteosarcoma of the retroperitoneum. The patient received adjuvant MAP chemotherapy (methotrexate, doxorubicin, cisplatin) and at 25 months after surgery remains free of recurrence or metastasis; surveillance imaging will continue for at least 10 years. Any osteoid-producing retroperitoneal sarcoma without a well-differentiated liposarcoma component should undergo MDM2 amplification testing, and ideally CDK4 testing, because the two diagnoses are managed differently.
SN  - 2296-858X
ER  -