CASE REPORT article
Front. Immunol.
Sec. Cancer Immunity and Immunotherapy
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
Jiameng Li
Xiaoyu Wang
Junhui Zhen
Mei Qi
Shandong University, Jinan, China
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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.
Summary
Keywords
fluorescence in situ hybridization (FISH), Pleomorphic undifferentiated sarcoma (UPS), Programmed death receptor ligand 1 (PD-L1), Renal pelvis, TP53
Received
17 December 2025
Accepted
17 February 2026
Copyright
© 2026 Li, Wang, Zhen and Qi. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
*Correspondence: Junhui Zhen; Mei Qi
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