案例報告：年輕男性發生罕見腎臟原發性滑液肉瘤

許玄昀¹, 吳敏瑞¹; 施孟宏²; 卓育慶¹, 陳進利¹, 蒙恩¹ ,于大雄¹

¹國防醫學院三軍總醫院外科部泌尿外科

²國軍高雄總醫院左營分院外科部

Young adult with rarely primary synovial sarcoma of kidney: a case report

Hsuan-Yun, Hsu¹, Min-Jui, Wu¹, Meng-Hung Shih², Yu-Cing Jhou¹, Chin-Li Chen¹, En Meng¹ ,Dah-Shyong Yu¹

¹ Division of Urology, Department of Surgery, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan

² Department of Surgery, Zuoying Branch of Kaohsiung Armed Forces General Hospital, Kaohsiung, Taiwan

Abstract

Synovial sarcoma is a kind of soft tissue sarcoma with well-regions of the extremities but rarely diagnosed in kidney. A 30-year-old male experienced primary renal synovial sarcoma (PRSS), then received laparoscopic radical nephrectomy. The gene test showed chromosomal translocation t (X; 18) and SYT-SSX-2 gene fusion. The pathology result showed renal no capsular invasion, considering localized lesion. The patient was doing well without adjuvant therapy at the 8-month follow-up. Routine detection of gene fusion type and if localized disease can help predict synovial sarcoma behavior and its relation to disease prognosis, and possible treatment without adjuvant therapy.

Introduction

Soft tissue sarcoma is a malignant tumor of mesenchymal origin with an incidence of less than 1–3% of all adult malignancies [1]. Synovial sarcoma is a type of soft tissue sarcoma that occurs in clinically well-defined regions of the extremities but is rarely diagnosed in visceral organs, lungs, and kidneys. Primary renal synovial sarcoma (PRSS) is rare and less than 200 PRSS cases have been reported [2]. Herein, we present the case of a 30-year-old man who was incidentally found to have PRSS and review the relevant literature.

Case Report

A 30-year-old man experienced painless gross hematuria for approximately 2 weeks and left flank pain. His medical history was unremarkable. Blood tests and biochemistry results were all within normal ranges. Ultrasonography of the kidney (Fig.1a) revealed a 3.8 cm hypoechoic mass over the lower pole of the left kidney. The abdominal computed tomography (CT) scan revealed a lesion mass, 5.0 cm in diameter, in the left kidney (Fig.1b). The tumor showed heterogeneous enhancement. Since malignancy could not be ruled out, a laparoscopic radical nephrectomy was performed.

The gross examination of the surgical specimen revealed a heterogeneous tumor mass with yellowish components (Fig.2A). The pathology results showed hypercellular spindle tumor cells arranged in a fascicular architecture without renal capsular invasion (Fig.2B). Immunohistochemical findings were as follows: positive for vimentin, CD99, and TLE-1, and negative for CK7, CK, desmin, EMA, S100, and WT-1. Molecular studies were performed to test for the t(X; 18) SYT/SSX fusion transcript using quantitative polymerase chain reaction (qPCR) (Fig.3). qPCR amplification was performed using fluorescent dye-labeled primers specific for SYT-SS18 and SYT-SSX genes. The results showed chromosomal translocation t(X; 18) and SYT-SSX-2 gene fusion (Fig.2B). The final pathology result indicated PRSS with SYT-SSX-2 gene fusion. The postoperative period was uneventful. The patient was doing well without adjuvant therapy at the 8-month follow-up.

Discussion

Synovial sarcoma originating in the kidney is extremely rare and accounts for less than an estimated 1–3% of all malignant neoplasms of the kidney [1]. Some features observed in imaging results help in the pre-treatment procedures. PRSS is usually seen as a well-defined mass of heterogeneous density with soft-tissue components and calcification and uneven enhancement on contrast view [3]. The features may be related to their histological subtypes but are usually not a characteristic of PRSS.

Histologically, synovial sarcoma can be divided into four types: biphasic, monophasic spindle cell type, monophasic epithelial type, and poorly differentiated type. Calcification is usually found in biphasic and monophasic types [4]. Immunohistochemical studies of PRSSs have consistently shown positivity for Bcl-2, CD99, CD56, vimentin, and negativity for desmin, CD34, and S100 protein [2, 5].

Synovial sarcoma is uniquely characterized by a chromosomal translocation t(X; 18)(p11.2; q11.2) and the consequent fusion gene SYT-SSX, both of which are considered essential for the diagnosis of synovial sarcoma. Routine detection of t(X;18) translocation by PCR may provide useful for the diagnosis of synovial sarcoma [6]. SS18-SSX oncoproteins cause deregulation of the tumor suppressor complexes BAF SMARCB1 and contribute to synovial sarcoma [7]. Histologically, the monophasic subtype closely related to SS18-SSX1 is more aggressive, which may explain the poorer prognosis observed. SYT- SSX2 fusion type presents with a lower prevalence of metastatic disease, and leads to a significantly better prognosis factor in terms of overall survival [8]. However, studies with more patients and longer follow-ups are needed to verify these observations, especially considering the conflicting data regarding the prognostic value of the SYT-SSX fusion protein.

Due to the rarity of the tumor, there are no standard treatments for the disease. Treatment options include surgical resection and chemotherapy. Adjuvant therapy for radical nephrectomy combined with chemotherapy (ifosfamide and doxorubicin) and surgery produce positive results. However, the data regarding the effects of chemotherapy on the often-aggressive PRSS are not consistent [9].

In our case, the pathology result indicated PRSS without renal capsular invasion and localized lesion. Renal capsular invasion has a poorer prognosis in renal cell carcinoma [10]. These were considered possible predictors of PRSS that showed localized disease. We also performed a gene examination. The gene expression type showed a positive prognosis for overall survival. Due to the gene type, lack of capsular invasion, and no recurrence observed in images at the 8-month follow-up, adjuvant therapy was not initiated. However, a longer follow-up period is needed for definitive results regarding the outcome.

Although rare, PRSS should be included in the differential diagnosis when adolescents or young adults present with renal neoplasms that appear as heterogeneous solid-cystic masses with clear boundaries and uneven enhancement. Histological results of renal capsular invasion may help define diseases as localized PRSS. Routine detection of t(X;18) translocation and gene fusion type can help diagnose synovial sarcoma and reflect its relation to disease prognosis, including tumor behavior and possible treatment without adjuvant therapy.