CASE REPORT article
Front. Oncol.
Sec. Cancer Genetics
Volume 15 - 2025 | doi: 10.3389/fonc.2025.1569160
Retroperitoneal dedifferentiated solitary fibrous tumor with unexpected Pax-2 expression, mimicking high grade clear cell renal cell carcinoma
Provisionally accepted
- 1Department of Pathology, First Affiliated Hospital of Nanjing Medical University, Nanjing, China
- 2Department of pathology, Women’s and Children’s Hospital Affiliated to Xiamen University (Xiamen Maternal and Child Health Care Hospital), Xiamen, China, Xiamen, China
- 3Department of Radiology, First Affiliated Hospital, Nanjing Medical University, Nanjing, Jiangsu Province, China
- 4Department of Orthopedics, First Affiliated Hospital, Nanjing Medical University, Nanjing, Liaoning Province, China
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Here, we report a case of retroperitoneal solitary fibrous tumor (SFT) in a 69-year-old Chinese woman. The patient had experienced lumbodorsal pain for more than two years. A computed tomography (CT) scan showed a mass adjacent to the right kidney, invading the surrounding soft tissues, measuring about 9.3 cm*8.4 cm. An incision biopsy was performed. Microscopically, the tumor was composed of sheets of epithelioid cells with round to ovoid nuclei, and abundant clear cytoplasm. The cells showed severe nuclear atypia and brisk mitosis, with thin-walled branched blood vessels set against a myxoid to collagenous background. By immunohistochemistry, the tumor cells exhibited diffuse and strong expression of CK-pan, Pax-2, P53, INI-1 and H3K27me3. Staining for CD34, S100, SOX10, TLE1, WT-1, and CK5/6 was negative. STAT6 staining was weak and indistinct. Furthermore, next generation sequencing (NGS) disclosed a rare NAB2-STAT6 (N5::S16) gene fusion, accompanied by a C141G missense mutation of TP53 gene. Consequently, a diagnosis of dedifferentiated SFT (DSFT) was determined, rather than high-grade clear cell renal cell carcinoma. The case demonstrated that DSFTs are prone to be misdiagnosed, particularly in atypical locations with abnormal morphology and immunophenotypes. In such circumstances, a comprehensive evaluation of clinical, pathological, and imaging studies is essential, and molecular examinations can provide valuable diagnostic support.
Keywords: Solitary fibrous tumor, Dedifferentiated, STAT6, PAX2, p53, next generation sequencing
Received: 31 Jan 2025; Accepted: 15 Apr 2025.
Copyright: © 2025 Wei, Yao, Zou, Wei, Fan and Gong. 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:
Qin-He Fan, Department of Pathology, First Affiliated Hospital of Nanjing Medical University, Nanjing, China
Qi-Xing Gong, Department of Pathology, First Affiliated Hospital of Nanjing Medical University, Nanjing, China
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