病例報告：罕見原發性腎臟滑膜肉瘤

吳英龍¹、張延驊^1,4、顏厥全²、彭昱璟³、黃逸修^1,4

台北榮民總醫院泌尿部¹；台北榮民總醫院腫瘤醫學部²；

台北榮民總醫院病理部³；

國立陽明交通大學醫學院泌尿學科及書田泌尿科學研究中心⁴ 

Case report: Rare cases of primary renal synovial sarcoma

Ying-Long Wu¹, Yen-Hwa Chang^1,4, Chueh-Chuan Yen², Yu-Ching Peng³, Eric Yi-Hsiu Huang^1,4

Department of Urology, Taipei Veterans General Hospital¹,

Department of Oncology, Taipei Veterans General Hospital²,

Department of Pathology, Taipei Veterans General Hospital³,

Department of Urology, College of Medicine and Shu-Tien Urological Science Research Center, National Yang Ming Chiao Tung University⁴, Taipei, Taiwan

           Case report

               Here we presented 2 rare cases of the primary renal synovial sarcoma.

First case, a 49-year-old male had been well until left flank pain happened one month before the presentation. There were no associated hematuria, dysuria nor abdominal pain. He sought evaluation at emergency department of other hospital. Computed tomography (CT) scan revealed a 12 cm cystic mass lesion with bleeding and pseudoaneurysm at left kidney interpolar region. Emergent embolization of the bleeding vessels was performed, and the patient then came to our urology clinic for second opinion.

The patient had history of hypertension and hyperlipidemia under medication. Laboratory tests   were WNL except mild renal function impairment (eGFR 58.40 ml/min). There was no family cancer history. He underwent left open radical nephrectomy on 2024/12/26 with uneventful recovery and was discharged at the 5th postoperative day. The pathology revealed renal synovial sarcoma with positive IHC stain for SS18-SSX. The diagnosis was further confirmed by Archer FusionPlex Sarcoma V2 Assay demonstrated “SS18(exon9):SSX2(exon6) fusion; Reads: [281] (14.79%)”. Due to the dismal outcome of this rare disease he was then transferred to MO for further management as recommended at MDT tumor boards. The follow-up CT scan at 3 months after surgery depicted 1.8 cm soft tissue lesion at retroperitoneum. He then received chemotherapy with Ifosfamide + Epirubicin for four cycles and the latest CT scan revealed the recurrent lesion decreased in size.

Another case had similar presentations. A 30-year-old man presented to the emergent department of other hospital because of left low back pain where CT scan showed a 4.8cm hypoenhancing mass at left kidney with bleeding. He was hospitalized for four days with conservative treatment. After discharge he visited our clinic for second opinion, since there was no associated symptoms and the lab tests were all WNL, after share decision making the patient preferred surveillance with close follow-up. However, severe left flank pain attacked again in ten days and repeated CT scan at our ER depicted more extensive re-bleeding of the tumor. The patient underwent emergent left radical nephrectomy on 2025/9/9 following a thorough discussion. The posts-operative period was smooth and the final pathological diagnosis confirmed left renal synovial sarcoma. The NGS testing FoundationOne Heme was performed and demonstrated SS18-SSX2 fusion. CT scan at one month after surgery showed a 1.0cm newly developed hypodense nodule at lateral segment of the liver favoring liver metastasis. He then was transferred to MO for systemic chemotherapy with Ifosfamide + Epirubicin since 2025/10/30.

Discussion

Synovial sarcoma (SS) is a translocation-defined soft-tissue sarcoma characterized by the SS18–SSX fusion oncogene, present in >95% of tumors and useful diagnostically on FISH/RT-PCR. In large series, adult 5-year cancer-specific survival is ~60% (higher in younger patients), but outcomes worsen with size >5 cm, deep location, and metastasis at diagnosis.

Primary renal synovial sarcoma (PRSS) is rare and aggressive. Systematic reviews and pooled series report median overall survival around 8-34 months, disease-free survival around 4-25 months, and recurrence approximately 40%; worse outcomes are seen with metastatic condition. Venous tumor thrombus appears relatively frequent. Radical nephrectomy is the cornerstone of therapy, which surgery is strongly associated with prolonged survival.

For systemic therapy, synovial sarcoma is relative chemosensitive among other sarcomas. Doxorubicin + ifosfamide remains first-line for treatment. Pazopanib serves as first line therapy for those with advanced synovial sarcoma and ineligible for intravenous chemotherapy and anthracycline-based regimen. Neoadjuvant radiotherapy is preferred to reduce the risk of tumor seeding to nearby organs in selective cases.

Novel adoptive cellular therapy has changed the metastatic landscape. In August 2024, the FDA approved afamitresgene autoleucel (Tecelra), a T-cell receptor (TCR) therapy targeting MAGE-A4, for previously treated unresectable/metastatic synovial sarcoma in HLA-A*02–positive patients with MAGE-A4–expressing tumors, marking the first approved TCR therapy in synovial sarcoma. Candidate selection requires HLA typing and companion diagnostic testing.

In summary, surgical resection remains the mainstay of treatment, and adjuvant chemotherapy is widely recognized and recommended. Molecular testing is strongly advised to aid diagnosis and guide therapeutic selection. Close surveillance is crucial, with imaging every 3 months during the first 2–3 years, followed by every 6 months for the subsequent 2 years.

Back to our patients, we successfully conducted the surgery, followed by timely systemic therapy and close monitoring. We would continue the current treatment algorithm and maintain intensive imaging surveillance given the high risk of recurrence.