Surgical management of prepubertal testicular tumors: A 30-year study in our institution.

OBJECTIVES: The 2021 European Association of Urology-European Society for Paediatric Urology guidelines on Pediatric Urology recommended testis-sparing surgery (TSS) as the primary approach to treat prepubertal testicular tumors exhibiting favorable preoperative ultrasound diagnoses. However, prepubertal testicular tumors are rare and clinical data regarding them is limited. Here, we analyzed the surgical management of prepubertal testicular tumors based on cases observed over approximately 30 years. METHODS: Data were retrospectively reviewed from medical records of consecutive patients aged <14 years with testicular tumors who received treatment at our institution between 1987 and 2020. We compared patients by their clinical characteristics, namely, those who underwent TSS versus radical orchiectomy (RO) and those who received surgery in 2005 onward versus prior to 2005. RESULTS: We identified 17 patients, with a median age at surgery of 3.2 years (range 0.6-14.0) and a median tumor size of 15 mm (range 6-67). The tumor size was significantly smaller in patients who underwent TSS than in those who underwent RO (p = 0.007). Patients treated in 2005 onward were more likely to undergo TSS than those treated prior to 2005 (71% vs. 10%, respectively), without significant differences in tumor size or the rate of preoperative ultrasound. No TSS cases required conversion to RO. CONCLUSIONS: Recent improvements in ultrasound imaging technology allow for more accurate clinical diagnosis. Therefore, the indications of TSS for prepubertal testicular tumors can be judged based not only on the tumor size but also on the diagnosis of benign tumors by preoperative ultrasound.

Transvesicoscopic ureteral reimplantation and ureteroscopy for management of primary obstructed non-refluxing megaureter with ureteral calculus.

Introduction: Primary obstructed non-refluxing megaureter, a type of congenitally dilated ureter, often resolves spontaneously. Surgery may be indicated in symptomatic cases; however, there are no reports of transvesicoscopic ureteral implantation and ureteroscopy for ureteral stones. Therefore, we describe the treatment of primary obstructed non-refluxing megaureter and ureteral calculi using this technique. Case presentation: A 6-year-old Japanese girl was referred for abdominal pain and gross hematuria due to right megaureter with multiple stones in the renal lower-pole calyces and ureter. She was diagnosed with primary obstructed non-refluxing megaureter and ureterovesical junction obstruction. The stones were removed using mini-percutaneous nephrolithotomy and transvesicoureteroscopic surgery, respectively. A narrow segment of the right ureter was cut, and transvesicoscopic ureteral plication and reimplantation were performed. The procedures were successful without postoperative complications. Conclusion: Transvesicoscopic ureteral reimplantation with ureteroscopy may be a safe, effective and minimally invasive surgical option for ureterovesical junction obstruction with ureteral stones.

Long-term survival of a patient with refractory advanced adrenocortical carcinoma after combination chemotherapy with paclitaxel and carboplatin plus mitotane.

Introduction: The prognosis of patients with unresectable adrenocortical carcinoma is poor. Mitotane is the first-line treatment for this disease, and etoposide/doxorubicin/cisplatin/mitotane therapy is recommended as first-line chemotherapy in unresponsive cases. We present a case of long-term survival following combination chemotherapy with paclitaxel and carboplatin plus mitotane to manage mitotane-refractory advanced adrenocortical carcinoma. Case presentation: A 49-year-old woman with a left adrenal tumor, lymph node metastasis around the aorta, and multiple liver metastases was treated with mitotane. The disease progressed despite mitotane therapy; thus, combination chemotherapy with paclitaxel and carboplatin plus mitotane was administered for 9 months. Primary adrenal resection was performed after the liver metastasis had completely dissapeared. She has remained alive for 20 years since her initial diagnosis while undergoing mitotane therapy. Conclusion: In this case, combination chemotherapy with paclitaxel and carboplatin plus mitotane effectively controlled advanced adrenocortical carcinoma.

A novel method of transvesicoscopic ureteral reimplantation of an ectopic ureter with a mate ureter in a duplex kidney.

INTRODUCTION: The reimplantation of an ectopic ureter is still performed as an open surgery, although laparoscopic or robot-assisted laparoscopic surgery has gained popularity as a minimally invasive treatment for pediatric urological disorders. CASE PRESENTATION: A 15-day-old Japanese boy was referred to our hospital with right hydronephrosis. A detailed examination revealed complete ureteral duplication on the right side and a dilated ectopic upper pole ureter, opening into the prostatic urethra. Since the patient had recurrent febrile urinary tract infections, we performed plication and ureteral reimplantation of the dilated ectopic ureter using a transvesicoscopic surgical method at the age of 2 years and 5 months. CONCLUSION: We safely performed transvesicoscopic ureteral reimplantation for an ectopic upper pole ureter with a mate ureter in a duplex kidney, following the detection of an ectopic ureter within the bladder, due to the prior understanding of the wrapping of both ureters in a common sheath.

A Novel Transvesicoscopic Ureteral Reimplantation Technique to Treat an Infantile Ectopic Ureter in a Single System.

An ectopic ureter is a significant urinary tract malformation often treated during early childhood and is surgically managed based on its condition. Generally, only extravesical ureteral reimplantation is available as a treatment option for an ectopic ureter with well-preserved renal function. This report describes a case of a 28-months-old girl with an ectopic ureter in a single system who experienced repeated febrile urinary tract infections, successfully treated using a transvesicoscopic ureteral reimplantation as a minimally invasive treatment. To the best of our knowledge, this is the first report of transvesicoscopic ureteral reimplantation for an ectopic ureter in a single system.

Low Serum Inhibin B/Follicle-Stimulating Hormones and Anti-Müllerian Hormone/Follicle-Stimulating Hormones Ratios as Markers of Decreased Germ Cells in Infants with Bilateral Cryptorchidism.

PURPOSE: In cryptorchidism, germ cell development failure presents from infancy and may be reflected by altered hormonal levels produced by Sertoli cells. Our object was to assess for associations between serum hormone levels and testicular histopathology in cryptorchidism with an infertility risk according to the pretreatment undescended testicular positions. MATERIALS AND METHODS: Prepubertal cryptorchid boys aged 7-91 (median 20) months who underwent orchidopexy between 2014 and 2019 were included (122 unilateral [median 19 months {range 7-91}], 23 bilateral [24 months {11-81}]). We evaluated the pretreatment testicular position and size; serum hormone levels; and the mean number of germ cells per tubule transverse section (G/T). We also performed a subgroup analysis of boys aged ≤24 months at orchidopexy. RESULTS: Serum inhibin B levels and G/T were significantly lower in bilateral than in unilateral cryptorchid boys (median 96 [range 46-197] pg/ml vs 125 [21-354] pg/ml, p=0.026; 0.20 [0-2.59] vs 0.65 [0-4.55], p <0.001, respectively). Inhibin B/follicle-stimulating hormones (FSH) and anti-Müllerian hormone (AMH)/FSH ratios were positively correlated with G/T in bilateral cryptorchid boys aged ≤24 months (12, p=0.008 and p=0.019, respectively). Low inhibin B/FSH and AMH/FSH ratios and high FSH were predictors of impaired G/T as per receiver operating characteristic curves (p=0.019, p=0.004 and p=0.004, respectively), whereas in unilateral cryptorchid boys aged ≤24 months, serum hormone levels and G/T did not differ with the pretreatment testicular positions. CONCLUSIONS: In bilateral cryptorchid boys aged ≤24 months at orchidopexy, low inhibin B/FSH and AMH/FSH ratios may reflect impaired G/T and future infertility risk.

Genetic and histopathological analysis of transverse testicular ectopia without persistent Müllerian duct syndrome: two case reports.

BACKGROUND: Transverse testicular ectopia (TTE) is a rare anomaly in which both testes descend through a single inguinal canal into the same hemiscrotum. Although almost 20-50% of patients with TTE exhibit persistent Müllerian duct syndrome (PMDS) and many genetic analyses have been performed, no reports have described the genes contributing to TTE without PMDS. Here, we report two cases of TTE without PMDS using immunohistochemical staining and genetic analysis. CASE PRESENTATION: Two Asian patients with TTE without PMDS were subjected to orchiopexy. We performed testicular biopsies during operation and obtained blood samples before the operation. Testicular tissues were stained for c-kit, placental alkaline phosphatase (PLAP), and undifferentiated embryonic cell transcription factor 1 (UTF1) to evaluate the presence of intratubular malignant germ cells. Additionally, we performed polymerase chain reaction-based direct sequencing to identify single nucleotide polymorphisms in genes associated with regression of the Müllerian duct and testicular descent (that is, anti-Müllerian hormone [AMH], AMH receptor 2 [AMHR2], insulin-like 3 [INSL3], and relaxin family peptide receptor 2 [RXFP2]). The three-dimensional structures of proteins were predicted using SWISS-MODEL. In immunohistochemical analysis, c-kit and UTF1 were positive, whereas PLAP was negative in three testicular tissue samples from the two patients. These features were also detected on the unaffected side. In variant analysis, common missense variants in the AMH gene (g.365G>T; c.165G>T; p.Ser49Ile [rs10407022]) were observed. All variants in INSL3 and RXFP2 genes were intronic or silent. CONCLUSIONS: Because UTF1, a specific marker of spermatogonial stem cell activity, was expressed in both the affected and unaffected sides in the testicular tissues of two patients, the risk of malignancy may be high in these patients. Although the etiology of TTE without PMDS remains unclear, our variant analysis results were consistent with previous reports, and variants in the AMH gene (rs10407022) may contribute to the specific phenotype of TTE without PMDS.

Appropriate timing of performing abdominal ultrasonography and termination of follow-up observation for antenatal grade 1 or 2 hydronephrosis.

BACKGROUND: Most cases of antenatal the Society of Fetal Urology (SFU) grade 1or 2 hydronephrosis (HN) improve or resolve spontaneously with conservative treatment. However, there is no consensus on the duration of follow-up for cases of grade 1or 2 HN. The aim of this study was to determine the need for continuous follow-up period and new management of children with antenatal grade 1or 2 HN. METHODS: Subjects underwent ultrasonographic assessment for HN according to the SFU classification. We retrospectively evaluated 112 patients with postnatal grade 1 HN and 69 with grade 2 HN using abdominal ultrasonography between January 2010 and December 2017. We examined the change in HN grade on repeat ultrasonography. Kaplan-Meier method was used to show the effect of HN grade on the rate of HN changes. RESULTS: The mean follow-up duration was 44.9 ± 36.4 months (range 12-274). Initial SFU grade 1 HN disappeared in 47.0% of cases at 12 months, 66.4% at 24 months and 73.2% at 48 months. Initial SFU grade 2 HN showed improvement in grade in 74.7% of cases at 12 months, 88.3% at 24 months and 89.5% at 48 months. However, 14.6% of SFU grade 1 and 2.8% of SFU grade 2 cases increased in grade and of the 17 cases, 16 cases worsened within the first 6 months. No cases with increased grade required pyeloplasty. Initial disappearance and later reappearance of HN occurred in 40.5% of SFU grade 1 and 2 cases. The mean duration of later reappearance of HN was 39.1 ± 36.2 months (range 12-137). No cases showed reappearance of HN after more than 1 year. CONCLUSIONS: Ultrasonography within the first 6 months was necessary for management of children with antenatal grade 1or 2 HN, because some patients showed worsening. After that, it is considered safe to spread the follow-up interval for stable cases. Most cases of grade 1or 2 HN resolved spontaneously, however a few cases reappeared within 1 year. Therefore, ultrasonography after 1 year was necessary in children with HN that spontaneously disappeared. The appropriate time to end the follow-up was considered to have been after 1 year or more has passed since the disappearance was confirmed.

Disorganization of claudin-11 and dysfunction of the blood-testis barrier during puberty in a cryptorchid rat model.

BACKGROUND: Cryptorchidism is known to impair spermatogenesis. The blood-testis barrier (BTB) becomes defined in seminiferous tubules around puberty and provides a suitable environment for germ cells. Little is known about the BTB in undescended testes (UDT). OBJECTIVES: To determine the role of BTB during puberty in UDT using a non-surgical cryptorchid rat model. MATERIAL AND METHODS: Unilateral cryptorchid male rats were intraperitoneally injected with non-steroidal antiandrogen during intrauterine development; the testes were harvested at 4, 5, and 6 weeks after birth. Testicular histology, expression levels of the BTB proteins (claudin-11, occludin, zonula occludens-1), and apoptotic cells were evaluated by immunohistochemistry, Western blotting, and TUNEL assay. The functionality of the BTB was investigated by electron microscopy using the lanthanum tracer method. RESULTS: The testicular histology of undescended testes 6 weeks after birth showed maturation arrest at the spermatocyte level. The BTB protein distributions were altered in the UDT, with a noticeable difference in claudin-11(CLDN11) localization from 4 to 5 weeks after birth between control and UDT samples. BTB protein levels were similar. More apoptotic germ cells were detected in the adluminal compartment of tubules in the UDT than in the control testes. Electron microscopy showed that the lanthanum tracer was limited to the BTB of control testes, whereas it penetrated the BTB of UDT. DISCUSSION: Here, loss of normal BTB function and impaired spermatogenesis were observed in UDT during puberty. CLDN11 is a pivotal tight junction protein belonging to the BTB. Tight junctions are considered as essential for normal spermatogenesis, and abnormal CLDN11 organization may cause UDT-associated male infertility. CONCLUSION: CLDN11 disorganization within the BTB may cause spermatogenic impairment, possibly by limiting the BTB function.

Robot-Assisted Radical Cystectomy for Pediatric Bladder Rhabdomyosarcoma.

Background: The standard treatments for muscle-invasive bladder cancer with no metastasis are total cystectomy and urinary diversion. Although robot-assisted radical cystectomy (RARC) was covered from April 2018 by the Japanese National Health Insurance system, and the number of RARC is increasing, there has been no pediatric case report on RARC in Japan. Case Presentation: We report the case of a 6-year-old Japanese girl who was referred to our hospital with the chief complaint of a vulvar tumor protrusion during defecation. We resected the tumor from her external urethral meatus, and transurethral resection for the residual partial bladder neck tumor was performed for both a definitive diagnosis and as a possible curative therapy. The pathologic diagnosis was an embryonic type of rhabdomyosarcoma. Although she was treated by chemotherapy combined with proton therapy, a residual tumor at the neck and a new lesion at the top of bladder were observed 2 years after initial treatment. Thus, RARC was performed. The surgical specimen was placed in an end-pouch and was then removed through the incised vaginal wall, with cosmetic consideration. A bilateral cutaneous ureterostomy was performed at the sites of the working ports for urinary diversion. In the future, we plan to perform abdominal wall catheterization. Postoperatively, she was treated with adjuvant chemotherapy. There was no recurrence for 19 months. Conclusion: Because she was a child, particularly a girl, the wounds should be small and inconspicuous considering the cosmetic aspect. Although the posterior aspect of the bladder seemed difficult to detach because of the adhesions, it was possible to safely perform RARC.

Detailed presurgical evaluation of a case of congenital bladder diverticulum.

Congenital bladder diverticulum is rare and is usually observed in male children. An 8-year-old Japanese boy was referred to a hospital with fever and gross hematuria and was treated with a course of antibiotics. Because the dilatation of the ureter was suspected by abdominal ultrasonographic examination, he was referred to our hospital. We diagnosed congenital bladder diverticulum by computed tomographic scan and carried out laparoscopic bladder diverticulectomy and extravesical ureteral reimplantation. Four years later, there was no recurrence of gross hematuria or urinary tract infection.

Can lichen sclerosus be diagnosed by preputial appearance or symptoms?

INTRODUCTION: Lichen sclerosus (LS), or balanitis xerotica obliterans, is a chronic, inflammatory disease accompanied by cicatrizing skin conditions resulting in pathologic phimosis. LS can be detected clinically by the whitish appearance of the glans or the foreskin, thickened, nonretractable foreskin, dysuria, and spraying. However, diagnosis is confirmed histopathologically. PURPOSE: The aim of this study was to investigate whether LS can be diagnosed on the basis of clinical manifestation and symptoms. PATIENTS AND METHODS: A retrospective analysis was performed, which included boys referred to our institutions for phimosis evaluation between May 2001 and December 2016. Pediatric urologists clinically diagnosed LS preoperatively. Boys with voiding problems, recurrent balanoposthitis, or who were unresponsive to topical steroid treatment underwent surgical treatment. Patients who underwent religious circumcisions were not included. RESULTS: Three-hundred twenty boys diagnosed with phimosis were identified, and 71 (22%) boys underwent surgery. Fifty-eight boys underwent complete or partial circumcision, and 13 boys underwent a dorsal slit or preputioplasty. Thirty foreskin samples were sent for histopathologic examination. Histopathologic evaluation showed evidence of LS in 13 of 30 (43%) circumcised boys, chronic inflammation in ten (33%), no abnormality in four (13%), dysplasia in two (7%), and acute inflammation in one (3%). In the 22 boys who were clinically diagnosed with LS, 13 patients had histopathologic evidence of LS (59%). Visually, eleven cases had whitish foreskins and 21 cases had thickened nonretractable foreskins, of which there were seven (64%) (P>0.05) and 12 (57%) (P<0.01) cases, respectively. These cases were histopathologically diagnosed with LS. Both whitish and thickened, nonretractable foreskin was observed in eight patients, of which seven (88%) (P<0.01) were also histologically diagnosed with LS. There was no correlation between histopathologic diagnosis and preoperative symptoms such as dysuria, ballooning, spraying, or penile pain (P>0.2). CONCLUSION: It is difficult to reliably distinguish whether a patient has histopathological LS by clinical findings alone.

Involvement of the bone morphogenic protein/SMAD signaling pathway in the etiology of congenital anomalies of the kidney and urinary tract accompanied by cryptorchidism.

BACKGROUND: Congenital anomalies of the kidney and urinary tract (CAKUT), such as renal dysplasia, hydronephrosis, or vesicoureteral reflux, are the most common causes of end-stage renal disease. However, the genetic etiology of CAKUT remains unclear. In this study, we performed whole exome sequencing (WES) to elucidate the genetic etiology of symptomatic CAKUT and CAKUT accompanied by cryptorchidism. METHODS: Three patients with unilateral renal dysplasia accompanied by ipsilateral cryptorchidism were included in this analysis. Genomic DNA was extracted from peripheral blood, and WES was performed. Disease-specific single nucleotide polymorphisms (SNPs) were determined by comparison with the human genome reference sequence (hg19). Additionally, we searched for SNPs that were common to all three patients, with a particular focus on the coding regions of the target genes. RESULTS: In total, 8710 SNPs were detected. Of the genes harboring these SNPs, 32 associated with renal or testicular development were selected for further analyses. Of these, eight genes (i.e., SMAD4, ITGA8, GRIP1, FREM1, FREM2, TNXB, BMP8B, and SALL1) carried a single amino acid substitution that was common to all three patients. In particular, SNPs in SMAD4 (His290Pro and His291Pro) have not been reported previously in patients with symptomatic CAKUT. Of the candidate genes, four genes (i.e., ITGA8, GRIP1, FREM1, and FREM2) were Fraser syndrome-related genes, encoding proteins that functionally converged on the glial cell-derived neurotrophic factor/RET/bone morphogenic protein (BMP) signaling pathways. As another candidate gene, the protein encoded by BMP8B activates the nuclear translocation of SMAD4, which regulates the expression of genes associated with the differentiation of primordial germ cells or testicular development. Additionally, BMP4, a member of the BMP family, regulates the interaction between metanephric mesenchyme and ureteric buds by suppressing GDNF. CONCLUSIONS: Taken together, our findings suggested that the development of the kidney and urinary tract is intimately linked with that of male reproductive organs via BMP/SMAD signaling pathways.

A Rare Case of Epididymal Abscess in an Infant Treated Successfully with Needle Aspiration.

A 5-month-old boy presented with right scrotal swelling. Color Doppler ultrasonography showed an encapsulated hypoechoic lesion with surrounding hyperemia in the right tail of the epididymis. We performed surgical exploration of the scrotum because it was not considered to be a typical epididymitis. During the operation, we aspirated pus from his right epididymis through a needle by referring to the color Doppler findings. This is the first case of epididymal abscess in an infant to be successfully diagnosed and treated with needle aspiration.

Genome-Wide Gene Expression Profiling of Randall's Plaques in Calcium Oxalate Stone Formers.

Randall plaques (RPs) can contribute to the formation of idiopathic calcium oxalate (CaOx) kidney stones; however, genes related to RP formation have not been identified. We previously reported the potential therapeutic role of osteopontin (OPN) and macrophages in CaOx kidney stone formation, discovered using genome-recombined mice and genome-wide analyses. Here, to characterize the genetic pathogenesis of RPs, we used microarrays and immunohistology to compare gene expression among renal papillary RP and non-RP tissues of 23 CaOx stone formers (SFs) (age- and sex-matched) and normal papillary tissue of seven controls. Transmission electron microscopy showed OPN and collagen expression inside and around RPs, respectively. Cluster analysis revealed that the papillary gene expression of CaOx SFs differed significantly from that of controls. Disease and function analysis of gene expression revealed activation of cellular hyperpolarization, reproductive development, and molecular transport in papillary tissue from RPs and non-RP regions of CaOx SFs. Compared with non-RP tissue, RP tissue showed upregulation (˃2-fold) of LCN2, IL11, PTGS1, GPX3, and MMD and downregulation (0.5-fold) of SLC12A1 and NALCN (P<0.01). In network and toxicity analyses, these genes associated with activated mitogen-activated protein kinase, the Akt/phosphatidylinositol 3-kinase pathway, and proinflammatory cytokines that cause renal injury and oxidative stress. Additionally, expression of proinflammatory cytokines, numbers of immune cells, and cellular apoptosis increased in RP tissue. This study establishes an association between genes related to renal dysfunction, proinflammation, oxidative stress, and ion transport and RP development in CaOx SFs.

Robot-assisted laparoscopic pyeloplasty for ureteropelvic junction obstruction: comparison between pediatric and adult patients-Japanese series.

Robotic-assisted procedures are gaining traction as a viable form of minimally invasive surgery in the field of reconstructive surgery. In this article, the aim is to present our initial experience and clinical outcomes of robot-assisted laparoscopic pyeloplasty (RAL-P). We performed RAL-P in 22 patients for the management of ureteropelvic junction obstruction between December 2012 and August 2015. The da Vinci® S surgical system was utilized for all cases. All procedures were performed via a transperitoneal approach. We assessed perioperative outcomes, and furthermore, compared between pediatric and adult patients undergoing this procedure. Dismembered procedures were performed in 19 patients. Three patients underwent Y-V plasty, and two patients who experienced failure during the primary pyeloplasty had to undergo reoperation. Although the console time for pediatric patients was significantly shorter than that of adults (123.1 ± 18.3, 162.4 ± 23.9 min, respectively, p < 0.001), success rate was not significantly different between pediatric and adults (100 vs 90 %, p = 0.512). According to a comparison of surgical outcomes by age, the console time was significantly shorter in pediatric than in adult patients. This finding may be attributable to the differences in intraabdominal fatty tissues. Besides, RAL-P with Y-V plasty was applicable even for cases of failed pyeloplasty. In conclusion, the surgical outcomes of RAL-P were favorable and safe for both pediatric and adult patients, and comparable to findings of previous reports. To our knowledge, this is the first report of a case series of RAL-P in Japan.

Adrenal Neuroblastoma in an Adult: Effect of Radiotherapy on Local Progression after Surgical Removal.

Here, we report the case of a 62-year-old man with neuroblastoma, which is extremely rare in adults. His tumor was resected, but it recurred four months later. Radiotherapy reduced tumor size, and the patient remained in good health three years after surgical tumor removal. The residual tumor and the treatments administered to this patient were evaluated. We have also reviewed the literature.

Hemiscrotal agenesis: Pathogenesis and management strategies.

Hemiscrotal agenesis is among the rarest anomalies in scrotal development disorders. As it has only been reported in three cases, the clinical manifestations remain unclear. We report a case of hemiscrotal agenesis with ipsilateral cryptorchidism. Based on the thermal assessment of the scrotum, concurrent scrotoplasty and orchiopexy were carried out, and the scrotoplasty improved the thermal environment of the fixed left testis. Furthermore, the low expression of androgen receptor and steroid-5-alpha-reductase, alpha polypeptide 2 in the affected side of the scrotum likely resulted in the characteristics of absent scrotal rugae, and pigmentation on histological and biological analyses. For future fertility, we believe that scrotoplasty should be considered as a management option for hemiscrotal agenesis.

Clear cell sarcoma of the kidney distinguished from synovial sarcoma using genetic analysis: a case report.

BACKGROUND: The most common pediatric renal neoplasm is Wilms tumor, but clear cell sarcoma of the kidney or synovial sarcoma of the kidney are also sometimes encountered. Accurate pathological diagnosis is important, because adjuvant therapies including chemotherapy and radiotherapy differ according to the pathological type. CASE PRESENTATION: A 9-year-old boy presented with a headache, and ultrasonography, computed tomography, and magnetic resonance imaging revealed a heterogeneous enhancement of soft tissue originating from the upper pole of the left kidney, measuring approximately 11.0 × 10.0 × 8.0 cm. A left radical nephrectomy was performed using an intraperitoneal approach through an anterior subcostal incision. Pathological examination suggested clear cell sarcoma of the kidney or synovial sarcoma of the kidney based on morphological and immunohistological features. Using genetic analysis, a final diagnosis of spindle cell pattern clear cell sarcoma of the kidney was made based on the absence of the SYT-SSX fusion gene. After adjuvant chemo-radiotherapy was administered, no recurrence or metastasis has been identified as of 60 months postoperatively. CONCLUSION: In this case, it was difficult to discriminate clear cell sarcoma of the kidney from synovial sarcoma of the kidney based on histopathological examination alone, and genetic analysis was required. Accurate pathological diagnosis of pediatric renal tumor is important for determining optimal treatment and preventing recurrence and metastasis.