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Xp11.2 translocation renal cell carcinomas (tRCC) are a rare and highly malignant type of renal cancer, lacking efficient diagnostic indicators and therapeutic targets. Through the analysis of public databases and our cohort, we identified NMRK2 as a potential diagnostic marker for distinguishing Xp11.2 tRCC from kidney renal clear cell carcinoma (KIRC) and kidney renal papillary cell carcinoma (KIRP) due to its specific upregulation in Xp11.2 tRCC tissues. Mechanistically, we discovered that TFE3 fusion protein binds to the promoter of the NMRK2 gene, leading to its upregulation. Importantly, we established RNA- and protein-based diagnostic methods for identifying Xp11.2 tRCC based on NMRK2 expression levels, and the diagnostic performance of our methods was comparable to a dual-color break-apart fluorescence in situ hybridization assay. Moreover, we successfully identified fresh Xp11.2 tRCC tissues after surgical excision using our diagnostic methods and established an immortalized Xp11.2 tRCC cell line for further research purposes. Functional studies revealed that NMRK2 promotes the progression of Xp11.2 tRCC by upregulating the NAD+/NADH ratio, and supplementation with ß-nicotinamide mononucleotide (NMN) or nicotinamide riboside chloride (NR), effectively rescued the phenotypes induced by the knockdown of NMRK2 in Xp11.2 tRCC. Taken together, these data introduce a new diagnostic indicator capable of accurately distinguishing Xp11.2 tRCC and highlight the possibility of developing novel targeted therapeutics. © 2024 The Pathological Society of Great Britain and Ireland.

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This report recounts the diagnostic workup of a pediatric female who presented with hematuria secondary to a large renal mass visualized on abdominal imaging. Histologic assessment and subsequent immunohistochemistry studies were performed. Intense, unequivocal immunohistochemical expression of TFE3 and alpha-methylacyl-CoA-racemase with corresponding negativity for carbonic anhydrase IX, along with highly distinctive clinical, radiologic, gross, and microscopic findings confirmed the diagnosis of a renal cell carcinoma with TFE3 gene rearrangement - the first ever reported case in the Philippines. This case highlights the vital role and significant diagnostic impact of reliable, affordable and accessible immunohistochemistry studies in low-resource settings where molecular modalities for evaluating rare diseases are largely unavailable. Recognition of distinctive morphologic, immunohistochemical, and cytogenetic features in childhood and adolescent renal malignancies allows for the timely institution of therapeutic interventions for this aggressive entity.

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Background: Renal cell carcinoma (RCC) with TFE3 gene fusion caused by Xp11.2 translocations is a rare RCC subtype. This tumor is typically seen in children, comprising 20‒40% of overall RCC cases compared to 1‒1.6% observed in adults. Xp11.2 RCC is associated with a poor prognosis due to both the progression of local lesions and early distant and lymphatic metastasis. Case presentation: A case of RCC with Xp11.2 RCC translocations and TFE3 gene fusion was found in a pediatric patient, illustrating the catastrophic effects of ignoring the condition. The tumor developed from a local lesion to lymph metastasis (3.2-12 cm) within 4 years. Despite ongoing controversy, surgical resection remains the most common and productive approach. In this patient, renal retroperitoneal lymph node dissection and radical nephrectomy of the left kidney were performed via laparoscopic surgery. The RCC-associated Xp11.2 translocation/TFE3 gene fusions were identified by postoperative pathology. Microscopic analysis showed the presence of intravascular cancer thrombus, renal sinus invasion, and cancer necrosis. The pathological stages were confirmed as PT3aN1M0 with a negative margin. Follow-up at 5 months showed that the patient recovered without the use of any adjuvant treatments. Conclusion: Our study highlights the natural course, diagnosis, and treatment of RCC-associated Xp11.2 translocation/TFE3 gene fusions, especially the necessity of early surgery. This case may be a helpful reference for urologists in the treatment of similar cases. It also serves as a precautionary signal for patients who neglect the renal neoplasm.

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The TFE3 fusion gene, byproduct of Xp11.2 translocation, is the diagnostic marker for translocation renal cell carcinoma (tRCC). Absence of any clinically recognized therapy for tRCC, pressing a need to create novel and efficient therapeutic approaches. Previous studies shown that stabilization of the G-quadruplex structure in oncogenes suppresses their expression machinery. To combat the oncogenesis caused by fusion genes, our objective is to locate and stabilize the G-quadruplex structure within the PRCC-TFE3 fusion gene. Using the Quadruplex-forming G Rich Sequences (QGRS) mapper and the Non-B DNA motif search tool (nBMST) online server, we found putative G-quadruplex forming sequences (PQS) in the PRCC-TFE3 fusion gene. Circular dichroism demonstrating a parallel G-quadruplex in the targeted sequence. Fluorescence and UV-vis spectroscopy results suggest that pyridostatin binds to this newly discovered G-quadruplex. The PCR stop assay, as well as transcriptional or translational inhibition using real time PCR and Dual luciferase assay, revealed that stable G-quadruplex formation affects biological processes. Confocal microscopy of HEK293T cells transfected with the fusion transcript confirmed G-quadruplexes formation in cell. This investigation may shed light on G-quadruplex's functions in fusion genes and may help in the development of therapies specifically targeted against fusion oncogenes, which would enhance the capability of current tRCC therapy approach.

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OBJECTIVE: This study aims to establish an effective predictive model for predicting Xp11.2 translocation/TFE3 gene fusion renal cell carcinoma (TFE3-RCC) and develop optimal therapeutic strategies. METHODS: Data from 4961 patients diagnosed with renal cell carcinoma at two medical centers in China were retrospectively analyzed. A cohort of 1571 patients from Zhejiang Provincial People's Hospital (Ra cohort) was selected to construct the model. Another cohort of 1124 patients from the Second Affiliated Hospital of Zhejiang Chinese Medical University was used for external validation (the Ha cohort). All patients with TFE3-RCC in both cohorts were included in the Ta cohort for the prognostic analysis. Univariate and multivariate binary logistic regression analyses were performed to identify independent predictors of the predictive nomogram. The apparent performance of the model was validated. Decision curve analysis was also performed to assess the clinical utility of the developed model. Factors associated with progression and prognosis in the Ta cohort were analyzed using the log-rank method, and Cox regression analysis and Kaplan-Meier survival curves were used to describe the effects of factors on prognosis and progression. RESULTS: Univariate and multivariate logistic regression analyses demonstrated that age, sex, BMI, smoking, eosinophils, and LDL were independent predictors of TFE3-RCC. Therefore, a predictive nomogram for TFE3-RCC, which had good discriminatory power (AUC = 0.796), was constructed. External validation (AUC = 0.806) also revealed good predictive ability. The calibration curves displayed good consistency between the predicted and observed incidences of TFE3-RCC. Invasion of regional lymph nodes, tyrosine kinase inhibitors, and surgical methods were independent factors associated with progression. Tyrosine kinase inhibitors are independent prognostic factors. CONCLUSION: This study not only proposed a high-precision clinical prediction model composed of various variables for the early diagnosis of Xp11.2 translocation/TFE3 gene fusion renal cell carcinoma but also optimized therapeutic strategies through prognostic analysis.

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Purpose To investigate the ultrasound imaging characteristics of Xp11.2 translocation/TFE3 gene fusion renal cell carcinoma(Xp11.2/TFE3-tRCC).Materials and Methods A retrospective analysis was conducted of 10 patients with pathologically confirmed Xp11.2/TFE3-tRCC who underwent surgery in West China Hospital of Sichuan University from April 2009 to February 2022.The ultrasonic images were collected and further analyzed,including tumor border,shape,internal echoes,Doppler findings,and contrast-enhanced ultrasonography findings.Results A total of 10 masses were finally included,4 of which underwent contrast-enhanced ultrasound.The ultrasonographic manifestations of Xp11.2/TFE3-tRCC showed diversity and variability,and the mass was most commonly located in the medulla(5 cases).Conventional ultrasound showed solid nodules with clear boundaries and regular shape similar to benign lesions in 6 cases,and color Doppler showed punctated blood flow signals in 5 cases.Contrast-enhanced ultrasound was more inclined to malignant tumors(3 cases),which showed uneven enhancement,mostly accompanied by peripheral uneven enhancement rings.Conclusion Xp11.2/TFE3-tRCC tends to be benign on conventional ultrasound,while contrast-enhanced ultrasound shows malignant lesions.Therefore,contrast enhanced ultrasound can serve as a potential diagnostic tool for suspected Xp11.2/TFE3-tRCC.

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Renal cell carcinoma (RCC) associated with Xp11.2 translocation/transcription factor E3 (TFE3) gene fusion is a rare subtype of RCC. A 31-year-old male patient was admitted to The Affiliated Hospital of Zunyi Medical University (Zunyi, China) with a solid mass in the left kidney during a routine health examination. After ruling out surgical contraindications, the patient underwent a laparoscopic left partial nephrectomy under general anesthesia. Postoperative pathology and fluorescence in situ hybridization (FISH) identified Xp11.2 translocation RCC. There was no tumor recurrence or metastasis during the 1-year follow-up. Xp11.2 translocation RCC is unusual, its clinical and imaging findings are not specific, and the diagnosis depends on TFE3-immunohistochemical assay and FISH analysis. Surgical resection is the first choice of treatment and its prognosis is worse than that of clear cell RCC, thus regular follow-ups are necessary.

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Translocation and transcription factor E3 (TFE3)-rearranged renal cell carcinoma (RCC) is a rare subtype of RCCs characterised by the fusion of the TFE3 transcription factor genes on chromosome Xp11.2 with one of the multiple genes. TFE3-rearranged RCC occurs mainly in children and adolescents, although middle-aged cases are also observed. As computed tomography (CT)/magnetic resonance imaging (MRI) findings of TFE3-rearranged RCC overlap with those of other RCCs, differential diagnosis is often challenging. In the present case reports, we highlighted the features of the fluorine-18-labelled fluorodeoxyglucose positron emission tomography with CT (FDG PET-CT) in TFE3-rearranged RCCs. Due to the rarity of the disease, FDG PET-CT features of TFE3-rearranged RCC have not yet been reported. In our cases, FDG PET-CT showed high standardised uptake values (SUVmax) of 7.14 and 6.25 for primary tumours. This might imply that TFE3-rearranged RCC has high malignant potential. This is conceivable when the molecular background of the disease is considered in terms of glucose metabolism. Our cases suggest that a high SUVmax of the primary tumour is a clinical characteristic of TFE3-rearranged RCCs.

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Background: Xp11.2 translocation/TFE3 gene fusion associated with renal cell carcinoma (Xp11.2 RCC) exhibits unique biological characteristics and is associated with an increased incidence of tumor thrombosis, lymph node metastasis, and advanced disease stages. Multimodality imaging, including US, contrast-enhanced CT, multi-parametric MRI, and 18F-FDG PET/CT plays a crucial role in the preoperative diagnosis and differentiation of renal tumors. Case report: A 15-year-old female presented with lumbar pain worsened, and developed persistent painless hematuria. The CT attenuation values of the scan without contrast, corticomedullary phase, nephrographic phase, and delayed phases were 35 HU, 83 HU, 82 HU, and 75 HU, respectively. The solid component of the mass displayed heterogeneous marked enhancement. Furthermore, MRU indicated that the lesion involved the cortical medulla and infringed on the renal sinus fat. The lesion appeared isosignal in T1WI, slightly low signal in T2WI, and slightly high signal in DWI. The degree of enhancement in the three phases of enhancement scan was lower than that in the renal parenchyma, and hemorrhage and necrosis were observed within the internal part of the lesion. To further clarify the staging, the patient underwent 18F-FDG PET/CT. PET/CT images showed multiple irregular occupancies in the right kidney with unclear borders, showing a heterogeneous increase in 18F-FDG uptake, with SUVmax values ranging from 2.3 to 5.2 in the routine imaging phase (60 min post-injection), compared to SUVmax values ranging from 2.8 to 6.9 in the delayed imaging phase (160 min post-injection). Additionally, multiple enlarged and fused lymph nodes were observed in the medial part of the right kidney and the retroperitoneum, exhibiting a heterogeneous increase in 18F-FDG uptake, with SUVmax values ranging from 4.1 to 8.7 in the routine imaging phase, compared to SUVmax values ranging from 4.4 to 9.1 in the delayed imaging phase. The postoperative pathology, immunohistochemistry, and molecular analysis of histiocytes were consistent with a diagnosis of Xp11.2 RCC. One month after surgery, enhanced-CT examination of the patient revealed lung metastasis, peritoneal metastasis, and multiple lymph node metastases throughout the body, with an overall survival of 16 months. Conclusion: Xp11.2 RCC exhibits unique biological characteristics and is associated with an increased incidence of tumor thrombosis, lymph node metastasis, and advanced disease stages. Long-term follow-up is essential to monitor the likelihood of recurrence and metastasis. 18F-FDG PET/CT examination can comprehensively visualize the lesion's location and extent, providing a basis for clinical tumor staging and aiding in treatment monitoring and follow-up. To address the limitations of FDG, the utilization of specific tracers designed for RCC or tracers that are not excreted via the urinary system would be ideal. Further advancements in molecular imaging technologies and the development of novel tracers hold great promise in advancing the diagnosis and management of RCC, ultimately contributing to better patient outcomes and overall disease management.

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Xp11.2 translocation renal cell carcinoma (Xp11.2 RCC) is a rare tumor, occurring more frequently in childhood than in adulthood. It results from Xp11.2 chromosome translocations and the fusion of the transcription factor E3 (TFE3) gene. In this context, we present a case report of an 18-year-old female who was diagnosed with Xp11.2 RCC following open radical nephrectomy and lymph node dissection on the left side. The histopathological analysis indicated stage T3aN1Mx disease, which was confirmed through immunohistochemistry (IHC) and fluorescent in situ hybridization (FISH). The patient remained under observation until March 2023 when systemic scans uncovered the presence of ascites, peritoneal carcinomatosis, and left supraclavicular lymphadenopathy. A subsequent biopsy reaffirmed the primary disease, leading to the planning of systemic treatment involving tyrosine kinase inhibitors (TKIs) and immunotherapy. However, due to financial constraints, the patient's treatment options were limited to sunitinib initially. The current plan involves reevaluation after three months using scans to determine the subsequent course of treatment. Our case report offers crucial insights into the clinical presentation, diagnosis, and treatment of this rare malignancy. This enhances medical understanding, guides research, and improves the management of similar cases. Case reports like this share practical experiences, shaping future studies and patient care.

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RCC accounts for only 0.1%-0.3% of all kidney tumors and 2%-6% of malignant kidney tumors in children. Accounting for approximately one-third of the total number of cases in children and adolescents with RCC, Xp11.2 tRCC is the most common subtype of the MiT family translocation renal cell carcinoma, which is a group of rare childhood and adult tumors, characterized by recurrent gene rearrangements of TFE3. Here we report a rare case of a 6-year-old male patient with MiT family translocation renal cell carcinoma (MiTF tRCC) where the patient developed retroperitoneal metastasis. The patient underwent partial nephrectomy (PN), radical nephrectomy (RN), abdominal lymph node resection, and intestinal adhesion lysis. Microscopically, we detected focal and nest clump-shaped clusters of tumor cells whose cytoplasm was bright and clear. Immunohistochemistry (IHC) showed tumor cells diffusely expressed TFE3, and fluorescence in situ hybridization (FISH) demonstrated disruption of the TFE3 locus, confirming the diagnosis of Xp11.2 tRCC, the most common subtype of MiTF tRCC. Eventually, the patient obtained a good therapeutic result. This case can provide a good reference and guidance for pediatric urologists and oncologists to recognize and diagnose rare renal cell carcinoma in children.

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Translocation-associated renal cell carcinoma (TRCC) is a group of under-recognized malignant renal neoplasms owing to the unavailability of ancillary diagnostic tools and considering the fact that these tumors may histomorphologically mimic a heterogeneous group of neoplasms ranging from benign to malignant ones. Xp11.2 translocation-associated renal cell carcinoma is a disease of the young with a relatively less known prognosis owing to the rarity of such reported neoplasms. The histological appearance of bulbous tumor cells with abundant, vacuolated cytoplasm and the presence of psammomatoid bodies are clues to the diagnosis but are not entirely specific. The immunohistochemistry (IHC) finding of transcription factor E3 (TFE3) positivity is an important pointer, but the demonstration of Xp11.2 translocation by fluorescence in situ hybridization (FISH) serves as the confirmatory test. In our case report, we highlight the fact that a combined approach involving light microscopy, immunohistochemistry, and fluorescence in situ hybridization is the key to its diagnosis.

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Cytomorphologic and immunocytochemical features of TFE3 translocation-associated renal cell carcinoma.

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Purpose: To analyze the imaging characteristics of Xp11.2/TFE3 translocation renal cell carcinoma and explore the relationship between the pathological features and imaging findings. Materials and Methods: Imaging, pathological, and clinical data of 28 patients with Xp11.2 RCC were studied from August 2013 to November 2019. The imaging characteristics and morbidity of different group were also explored meanwhile. Results: Patients ranged from 3 to 83 years old and the median age was 47 years. Bilateral renal tumors were detected in 1 patient and unilateral in the rest 27 patients. Out of 29 tumors, 13 were in the left kidneys and 16 in the right. Tumor size ranged from 2.2 cm × 2.5 cm to 20.0 cm × 9.7 cm. Tumors were cystic component/necrosis (29/29,100%), renal capsule breakage (16/29, 55%), capsule (18/29, 62%), calcification (15/29, 52%), fat (4/29, 14%), and metastasis (10/29, 34%). Tumors showed moderate enhancement during renal corticomedullary phase and delayed enhancement during nephrographic and excretory phase. The solid parts showed hypointense on T2WI. The imaging characteristics did not have significant correlation with the age, the incidence of adolescent and children group was higher than adult group. Conclusion: Xp11.2 RCC is a well-defined mass with cystic component, the solid part of tumor showed hypointense on T2WI. Xp11.2 RCC showed moderate enhancement during the renal corticomedullary phase and delayed enhancement during the nephrographic phase and excretory phase. Xp11.2 RCC has a higher incidence in children.

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Background: Xp11.2 translocation renal cell carcinoma (Xp11.2 tRCC) is a group of rare and highly heterogeneous renal cell carcinoma (RCC). The translocation involving TFE3 and different fusion partners lead to overexpression of the chimeric protein. The purpose of this study is to explore the clinicopathological features of Xp11.2 tRCC with four common fusion subtypes. Methods: We screened out 40 Xp11.2 tRCC patients from January 2007 to August 2021 in our institution. The diagnosis was initially confirmed by TFE3 immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH) assay and their fusion partners were verified by RNA sequencing. Then the 40 cases were divided into two groups (DBHS family and non-DBHS family group) and a clinical comparison among the four common fusion subtypes was performed. Results: Among the 40 cases, 11 cases with SFPQ-TFE3 gene fusion and 7 cases with NONO-TFE3 gene fusion were classified in DBHS group, the remaining cases with ASPL-TFE3 (11 cases) or PRCC-TFE3 (11 cases) gene fusion were classified in non-DBHS group. Lymph node (LN) metastasis (P=0.027) and distant metastasis (P=0.009) were more common seen in non-DBHS family group than DBHS family group and cases in DBHS family group have better progressive-free survival (PFS) (P=0.02). In addition, ASPL-TFE3 fusion was associated with worse outcome (P=0.03) while NONO-TFE3 fusion (P=0.04) predicted a better prognosis. Conclusions: Different fusion partner genes may play a functional role in various morphology, molecular and biological features of Xp11.2 tRCCs. The impact of fusion partners on clinical characteristics of Xp11.2 tRCCs deserves further exploration.

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Background: This study aimed to investigate the expression profile of TFE3 in renal cell carcinoma (RCC) and the clinicopathological features as well as prognosis of TFE3-positive RCC. Methods: Tissue sections from 796 patients with RCC were collected for immunohistochemical staining of TFE3. Molecular TFE3 rearrangement tests were also carried out on the TFE3-positive RCCs using fluorescence in situ hybridization and RNA-sequencing assays. Both clinicopathological features and follow-up information were collected for further analysis. Results: The present study showed that 91 patients with RCC (91/796, 11.4%) were TFE3 positive expression but only 31 (31/91, 34.1%) of the patients were diagnosed with Xp11.2 translocation RCC. Further, it was found that the patients with TFE3-positive RCCs were more likely to develop lymph node and distant metastasis at diagnosis as well as presented a significantly higher WHO/ISUP nuclear grade and AJCC stage as compared with patients with TFE3-negative RCCs (p<0.01). Results of univariate and multivariate analyses showed that TFE3 positive expression was an independent prognostic factor associated with poor progression-free survival. Further, the findings of survival analysis showed that patients with positive TFE3 expression showed a shorter progression-free survival as compared with the patients with negative expression of TFE3 (p<0.001). In addition, results of the survival analysis found that there was no significant difference in progression-free survival between the Xp11.2 translocation RCC and TFE3-positive non-Xp11.2 translocation RCC groups (p=0.9607). Conclusion: This study found that nuclear TFE3 expression is not specific to the Xp11.2 translocation RCC. Moreover, the positive TFE3 expression is associated with tumor progression and poor prognosis in patients with RCC irrespective of the presence of TFE3 translocation.

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BACKGROUND: Renal cell carcinoma (RCC) with Xp11.2 translocation/TFE3 gene fusion is a rare and distinct subtype of RCC that is classified under tumors with translocation of the microphthalmia-associated transcriptional factor. CASE SUMMARY: We report an adult case of Xp11.2 translocation advanced RCC with metastasis (T3aN1M1), after targeted treatment, alcohol ablation, and transarterial chemoembolization, who eventually underwent successful surgical excision. No recurrence or transfer was seen within one year, and the survival period was more than 3 years. A review of the relevant literature was conducted to improve our understanding of the pathogenesis, epidemiology, clinical manifestations, diagnosis, differential diagnosis, treatment, and other aspects of the disease. CONCLUSION: Transarterial chemoembolization and ablation did not achieve the desired tumor reduction in this patient, but had a significant effect on reducing intraoperative bleeding and inhibiting tumor activity.

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Renal cell carcinoma (RCC) associated with Xp11.2 translocation/TFE3 gene fusions is a rare subtype of renal tumor. This entity predominantly occurs in juveniles, but rarely in adults. Xp11.2 translocation RCC (tRCC) patients with lymph node or organ metastasis are associated with poor prognosis, and the strategy remains controversial. Herein, we presented our experience with the diagnosis and treatment of an adult case of Xp11.2 tRCC. In our clinical practice, a 32-year-old male manifested fever and right flank paroxysmal blunt pain, and computed tomography showed an inhomogeneous mass, 6 cm in diameter, in the right kidney. Then right partial nephrectomy (PN) and renal hilar lymph node dissection by laparoscopic surgery were performed. Pathology revealed that the tumor cells were positive for TFE3 immunohistologically and positive for TFE3 break-apart fluorescence in situ hybridization assay. A splice site mutation c.1544-1G>T of protein tyrosine phosphatase receptor delta (PTPRD) was detected by next-generation sequencing and weak PTPRD expression was confirmed in tumor tissues compared to tumor periphery. This patient was diagnosed with stage III RCC and received immune checkpoint inhibitor (camrelizumab) in combination with tyrosine kinase inhibitor (axitinib) treatment for 1 year. He achieved a clinical complete response with no sign of recurrence or metastasis. PTPRD mutation might be a favorable indicator for Xp11.2 tRCC patients managed by PN and followed by the adjuvant therapy of immune checkpoint inhibitor and tyrosine kinase inhibitor.

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PURPOSE: To report the clinicopathological features and mid- to long-term oncologic results of Xp11.2 translocation/transcription factor E3 (TFE3) gene fusion renal cell carcinomas (Xp11.2 translocation RCCs) in a single large-volume centrecentre. METHODS: Clinical and follow-up data of 46 patients who were diagnosed with Xp11.2 translocation RCC and underwentunderwent surgical intervention were retrospectively reviewed. RESULT: Forty-six Xp11.2 translocation RCC patients were identified from 4218 renal tumour patients who were underwentunderwent surgery in our centrecentre from Jan. 2014 to Apr. 2020. The incidence of Xp11.2 translocation RCCs in our centre was 1.09%. During a median follow-up period of 30.5 months, 4 patients died of the disease. The total median overall survival and cancer specific survival were 30.0 months and 24.0 months, respectively. The 1-year, 3-year and 5-year OS rates were 97.4%, 88.8%, and 88.8%, respectively. In multivariable analysis, displaying symptoms when diagnosed (p = 0.019), lymph node metastasis (p = 0.002) and distal metastasis (p = 0.020) were identified as risk factors for poor prognosis. CONCLUSION: Xp11.2 translocation RCC is a type of renal cell carcinoma with a relatively low incidence and various prognoses. Early-stage Xp11.2 translocation RCCs have a similar prognosis to most typical RCCs, but late-stage Xp11.2 translocation RCCs can lead to poor oncological outcomes.

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TFE3-rearranged renal cell carcinoma (RCC) is a rare but well characterised histological subtype of RCC with an aggressive clinical course and propensity for late metastases. Osseous metaplasia is an uncommon but well documented finding in clear cell, papillary and chromophobe RCC. We present the first case of a TFE3-rearranged RCC to be found harbouring metaplastic bone in a 47-year-old woman who presented with a slowly enlarging left flank mass over a 10 year period. This case report adds to the clinicopathological description of TFE3-rearranged RCC and suggests that larger studies are required to fully elucidate the prognosis of these tumours.