原發性腎臟滑膜肉瘤：病例報告及文獻回顧

¹陳柏衡、¹李致樵

¹台灣基督長老教會馬偕醫療財團法人馬偕紀念醫院

Primary renal synovial sarcoma: a case report and literature review

¹Bo-Heng Chen, ¹Chih-Chiao Lee

¹Department of Urology, MacKay Memorial Hospital, Taipei, Taiwan

Background:

Synovial sarcoma (SS) is a rare mesenchymal malignancy, accounting for 5–10% of soft tissue sarcomas[1]. SS typically arises in para-articular regions but can also occur in atypical sites, including the kidneys. Primary renal SS was first described by Faria et al. in 1999. Renal synovial sarcoma is the least common variant of renal sarcomas, constituting less than 1% of all renal masses and typically affecting young adults aged 20 to 50. It is characterized by the cytogenetic abnormality t(X;18)(p11;q11), which leads to the presence of fusion proteins such as SYT-SSX1, SYT-SSX2, and SYT-SSX4. Its rarity poses diagnostic challenges, as it may be misidentified as metastatic disease or other renal neoplasms due to overlapping histological features. In this case report, we present a unique case of primary synovial sarcoma of the kidney, highlighting the crucial role of genetic analysis in achieving an accurate diagnosis and guiding treatment.

Case presentation:

A 71-year-old male with intermittent hematuria and urinary frequency for one week was referred to our center. A computed tomography (CT) scan showed a 10.4x10.0x13.3 cm renal mass with extension into the left renal vein(Figure 1.). The patient underwent left radical nephrectomy (Figure 2.). Histopathology confirmed a poorly differentiated synovial sarcoma, grade III, with a high mitotic rate and venous invasion. The tumor cells were diffusely positive for CD99 and SS18-SSX fusion-specific antibody.. The patient received three cycles of chemotherapy with AIM (Mesna + Doxorubicin + Ifosfamide). A follow-up CT scan three months after radical nephrectomy revealed a mass anterior to the spleen, suspected to be a seeding tumor or metastatic conglomerate lymph tissue. Consequently, the patient underwent video-assisted thoracoscopic surgery for pulmonary metastases in the right middle and lower lung lobes. One year postoperatively, the patient remains free of local recurrence or metastasis.

Discussion:

Primary renal synovial sarcoma (PRSS) is a rare subtype of renal sarcoma, representing 5-10% of all soft tissue sarcomas, and is typically associated with the t(X;18)(p11.2;q11.2) translocation. PRSS predominantly affects individuals around 36 years old, with a slightly higher incidence in males.[2] While synovial sarcomas commonly appear in extremities near joints, they can also develop in atypical sites like the kidneys, suggesting that these tumors may arise in areas without synovial membranes.

Symptoms of PRSS include painless hematuria, intermittent abdominal or lumbar pain, and, in some cases, a palpable abdominal mass. Metastasis, mainly to the lungs, occurs in 36.4% of cases and can lead to symptoms like hemoptysis. Despite adequate surgical margins, PRSS has a recurrence rate between 30% and 50%, with disease-free intervals of only 5 to 32 months.[3] .Diagnostic imaging, including ultrasound, CT, and MRI, can suggest PRSS but cannot definitively differentiate it from other renal sarcomas. Biopsy with immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH) to detect the SYT-SSX fusion gene is essential for confirming PRSS. Histologically, PRSS shows spindle cells arranged in fascicles with hyperchromatic nuclei and, often, a perivascular pattern. Synovial sarcomas are classified into monophasic, biphasic, and poorly differentiated types, with the monophasic type being most common. The SYT-SSX fusion gene plays a role in tumor biology and prognosis, with the SYT-SSX2 fusion gene associated with higher metastasis-free survival.[4] Primary renal synovial sarcoma is one of the most biologically aggressive cancers, posing significant challenges to conventional treatments. Surgical resection alone does not guarantee long-term survival, and alternative therapies like radiotherapy and chemotherapy have shown limited effectiveness. The rarity of synovial sarcomas has limited comprehensive studies, and follow-up periods in most cases have been short, with incomplete documentation of disease progression.[5]

Conclusion:

In conclusion, this case of primary renal synovial sarcoma highlights the importance of genetic analysis in diagnosing rare renal tumors. As our understanding of PRSS deepens, so will our ability to provide effective, evidence-based management for affected patients. Further research is necessary to develop best practices for diagnosing and treating this uncommon malignancy.