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March 6, 2026Frontiers in Immunology0 citationsOpen Access

Case Report: A rare case of primary undifferentiated pleomorphic sarcoma of the renal pelvis with high PD-L1 expression and a misleading positive urine FISH

JLJiameng LiXWXiaoyu WangJZJunhui Zhen

Key Result

Intravenous bevacizumab therapy post-nephroureterectomy resulted in no recurrence or metastasis at 28 months follow-up in a patient with primary renal pelvic undifferentiated pleomorphic sarcoma.

Key Points

  • This report examines a unique case of primary undifferentiated pleomorphic sarcoma, focusing on diagnosis challenges and treatment implications.
  • Case report of a patient with primary UPS of the renal pelvis
  • Assessment of urine FISH results
  • Evaluation of PD-L1 expression levels
  • Positive urine FISH results were misleading for urothelial carcinoma
  • High PD-L1 expression was observed in the tumor
  • Diagnosis complications were noted due to the non-specific characteristics of the malignancy

Study Design

Type

Case Report (n=1)

Multicenter

No

Structured PICO

P
Population
1 75-year-old female patient with primary undifferentiated pleomorphic sarcoma (UPS) of the renal pelvis, presenting with persistent gross hematuria and a renal pelvic mass.
I
Intervention
Left nephroureterectomy including kidney, ureter, and partial bladder resection, followed by intravenous bevacizumab therapy for over a year.
O
Outcome
Recurrence or metastasis

This case provides the first evidence that primary undifferentiated pleomorphic sarcoma of the renal pelvis can yield a false-positive urine FISH and exhibit high PD-L1 expression, suggesting a potential role for targeted therapy.

Limitations

  • Single patient case report limits generalizability
  • No control or comparator group
  • No randomized or blinded methodology
  • Lack of long-term follow-up beyond 28 months
  • Unclear dosage and regimen details for bevacizumab therapy

Abstract

Primary undifferentiated pleomorphic sarcoma (UPS) of the renal pelvis is an extremely rare and aggressive mesenchymal malignancy. The diagnosis remains challenged, and its clinical characteristics and treatment strategies remain unclear. Urine fluorescence in situ hybridization (FISH) is a highly sensitive tool for detecting urothelial carcinoma (UC), but ‘false’-positive results can be observed in non-UC malignancies. We present a challenging case of primary UPS of renal pelvis with positive urine FISH and high programmed death receptor ligand 1 (PD-L1) expression, which complicates the initial diagnosis and opens avenues for potential immunotherapy.

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Cite This Study

Li et al. (2026) conducted a case report in A 75-year-old female patient with primary undifferentiated pleomorphic sarcoma of the renal pelvis presenting with gross hematuria and a renal pelvic mass (n=1). Intravenous bevacizumab therapy was evaluated on Recurrence or metastasis rate after nephroureterectomy and bevacizumab therapy. Intravenous bevacizumab therapy post-nephroureterectomy resulted in no recurrence or metastasis at 28 months follow-up in a patient with primary renal pelvic undifferentiated pleomorphic sarcoma.

synapsesocial.com/papers/69aa7008531e4c4a9ff59707https://doi.org/10.3389/fimmu.2026.1769769
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