Retroperitoneal soft tissue sarcoma, a rare mimic and important differential of iliopsoas abscess


  • Ryan J. Green Department of Radiology, Cairns Base Hospital, Queensland, Australia
  • Sarath Vennam Department of Radiology, Royal Cornwall Hospital, UK
  • Corey Kirkham Department of Radiology, Cairns Base Hospital, Queensland, Australia
  • Conor Aylward Department of Radiology, Cairns Base Hospital, Queensland, Australia
  • William Caufield Department of Radiology, Cairns Base Hospital, Queensland, Australia
  • Lucy Andraloj Department of Radiology, Royal Cornwall Hospital, UK
  • Miles Geldart Department of Radiology, Royal Cornwall Hospital, UK
  • James Sellars Department of Radiology, Cairns Base Hospital, Queensland, Australia



STS, Iliopsoas abscess, Interventional radiology


This case report highlights the diagnostic challenges posed by retroperitoneal soft tissue sarcoma (STS) presenting as an iliopsoas abscess, mimicking common symptoms and radiological findings. This patients’ symptoms recurred despite multiple percutaneous drains and revisions over a period of months. Further investigation revealed a partly solid, partly cystic mass consistent with sarcoma. Surgical excision confirmed the diagnosis, but recurrence necessitated palliation. This case emphasizes the importance of differential diagnoses of iliopsoas collection and the need for research into alternative imaging modalities to aid clinicians and radiologists in differentiating benign retroperitoneal collections from malignancy.


Munoz P, Bretcha-Boix P, Artigas V, Asencio JM. Surgical Principles of Primary Retroperitoneal Sarcoma in the Era of Personalized Treatment: A Review of the Frontline Extended Surgery. Cancers. 2022;14(17):4091.

Chern CH, Hu SC, Kao WF, Tsai J, Yen D, Lee CH. Psoas abscess: making an early diagnosis in the ED. Am J Emerg Med. 1997;15(1):83-8.

Siegel RL, Miller KD, Jemal A. Cancer statistics, 2015. CA Cancer J Clin. 2015;65(1):5-29.

Soft Tissue Sarcoma Treatment (PDQ®)-NCI. 2024. Available at: Accessed on 28 May 2024.

SEER. SEER Cancer Statistics Review, 1975-2017. Available at: index.html. Accessed on 28 May 2024.

Porter GA, Baxter NN, Pisters PWT. Retroperitoneal sarcoma: a population-based analysis of epidemiology, surgery, and radiotherapy. Cancer. 2006;106(7):1610-6.

Smrke A, Wang Y, Simmons C. Update on systemic therapy for advanced soft-tissue sarcoma. Curr Oncol. 2020;27(1):25-33.

Roeder F. Radiation Therapy in Adult Soft Tissue Sarcoma-Current Knowledge and Future Directions: A Review and Expert Opinion-PMC. Cancers (Basel). 2020;12(11):3242.

Bartolo DCC, Ebbs SR, Cooper MJ. Psoas abscess in Bristol: a 10-year review. Int J Colorectal Dis. 1987;2(2):72-6.

Gruenwald I, Abrahamson J, Cohen O. Psoas abscess: case report and review of the literature. J Urol. 1992;147(6):1624-6.

Tabrizian P, Nguyen SQ, Greenstein A, Rajhbeharrysingh U, Divino CM. Management and Treatment of Iliopsoas Abscess. Arch Surg. 2009;144(10):946-9.

Rieber A, Wruk D, Potthast S, Nüssle K, Reinshagen M, Adler G, et al. Diagnostic imaging in Crohn’s disease: comparison of magnetic resonance imaging and conventional imaging methods. Int J Colorectal Dis. 2000;15(3):176-81.

Mynter H. Acute Psoitis. Buffalo Med Surg J. 1881;21(5):202-10.

Elsayes KM, Staveteig PT, Narra VR, Chen ZM, Moustafa YL, Brown J. Retroperitoneal masses: magnetic resonance imaging findings with pathologic correlation. Curr Probl Diagn Radiol. 2007;36(3):97-106.

Nieweg OE, Pruim J, van Ginkel RJ, Hoekstra HJ, Paans AM, Molenaar WM, et al. Fluorine-18-fluorodeoxyglucose PET imaging of soft-tissue sarcoma. J Nucl Med Off Publ Soc Nucl Med. 1996;37(2):257-61.

Aoki J, Endo K, Watanabe H, Shinozaki T, Yanagawa T, Ahmed AR, et al. FDG-PET for evaluating musculoskeletal tumors: a review. J Orthop Sci Off J Jpn Orthop Assoc. 2003;8(3):435-41.

Lucas JD, O’Doherty MJ, Cronin BF, Marsden PK, Lodge MA, McKee PH, et al. Prospective evaluation of soft tissue masses and sarcomas using fluorodeoxyglucose positron emission tomography. Br J Surg. 1999;86(4):550-6.

Ioannidis JPA, Lau J. 18F-FDG PET for the diagnosis and grading of soft-tissue sarcoma: a meta-analysis. J Nucl Med. 2003;44(5):717-24.






Case Reports