TFEB ‐translocated and ‐amplified renal cell carcinoma with VEGFA co‐amplification: A case of long‐term control by multimodal therapy including a vascular endothelial growth factor‐receptor inhibitor

Introduction Renal cell carcinoma with TFEB amplification is rare and reportedly aggressive. We herein report a case of renal cell carcinoma with TFEB translocation and amplification in which long‐term control was achieved by multimodal therapy including a vascular endothelial growth factor ‐receptor inhibitor. Case presentation A 70‐year‐old man was referred to our institution for the treatment of renal cell carcinoma with multinodal metastases. Open nephrectomy and lymph node dissection were performed. Immunohistochemistry for transcription factor EB was positive, and fluorescent in situ hybridization revealed TFEB rearrangement and amplification. The diagnosis was TFEB‐translocated and ‐amplified renal cell carcinoma. VEGFA amplification was also demonstrated by fluorescent in situ hybridization. The residual and recurrent tumors were treated and controlled for 52 months by vascular endothelial growth factor‐receptor target therapy, radiation therapy, and additional surgery. Conclusion A good long‐term response to anti‐vascular endothelial growth factor drug therapy may be due to VEGFA amplification and subsequent vascular endothelial growth factor overexpression.


Introduction
In the 2016 WHO classification, TFEB-translocated RCC first emerged. In the 2022 WHO classification, rarer TFEB-amplified RCC was first included in the "TFEB-altered RCCs" group. 1 Some investigators have reported its aggressive nature and concurrent VEGFA gene amplification. 2 We herein report a case of TFEB-translocated and -amplified RCC for which we achieved long-term control by multimodal therapy, including a VEGFR inhibitor.

Case presentation
A 70-year-old man was referred to our institution for treatment of a right kidney tumor. The tumor was incidentally detected on a computed tomography (CT) scan. The CT scan (Fig. 1a-e) revealed a right kidney tumor with a maximum diameter of 12 cm accompanied by lymph adenopathy in the inter-aortocaval, para-aortic, external iliac, and mediastinal regions. No visceral metastasis was observed. The clinical diagnosis was metastatic RCC. Open nephrectomy and lymph node dissection were performed. The mediastinal lesions were not resected because of the difficulty in approaching them. Macroscopically, a brown-black tumor measuring 12 9 10 9 8 cm showed expansive growth (Fig. 2). Microscopic examination revealed a solid, partly cystic structure of tumor cells with large eosinophilic cytoplasm containing abundant melanin (Fig. 3a). Immunohistochemistry was positive for AE1/3, PAX8, and melan A and negative for alpha-smooth muscle actin. Therefore, melanoma and epithelioid angiomyolipoma were ruled out. We suspected MiT family translocation RCC as melanin-producing RCC. Immunohistochemistry was positive for TFEB ( Fig. 3b) and negative for TFE3. FISH using a TFEB split probe (GSP Lab., Inc., Kobe, Japan) was carried out to attain a definitive diagnosis (Fig. 4a). TFEB rearrangement was confirmed. Additionally, TFEB gene signals were remarkably increased, indicating TFEB amplification. FISH using a MALAT1-TFEB fusion probe (GSP Lab., Inc.) did not demonstrate MALAT1-TFEB gene fusion (Fig. 4b). Based on the above results, although the TFEB fusion partner gene was not identified, the diagnosis was TFEB-translocated and -amplified RCC. In addition, FISH using a VEGFA probe and the Chromosome 6 Control Probe (Empire Genomics, Buffalo, NY, USA) was performed (Fig. 4c). The results indicated VEGFA amplification without chromosomal amplification.
Because the mediastinal lesions remained unresected, pazopanib was administered. We did not select a combination of tyrosine kinase inhibitor and immunotherapy because they were not standard at that time. Two weeks after administration, pazopanib was discontinued because of liver dysfunction, and axitinib was started. Immediate shrinkage of the lesions was observed (Fig. 1f). Two years after administration of axitinib, positron emission tomography-CT revealed no new lesions. Radiation therapy was performed on the mediastinal lesions, and axitinib was discontinued. Six months later, a metastatic lesion was found in the para-aortic region. We performed laparoscopic resection, and the microscopic findings revealed almost the same tissue as the primary tumor. Three months later, a CT scan revealed new presacral lesions. After  re-administration of axitinib, shrinkage of the presacral lesions was observed. However, liver metastasis was noted on a CT scan 18 months after axitinib re-administration, and nivolumab was initiated. Nevertheless, the disease was controlled for 52 months by multimodal treatment.

Discussion
In this report, we presented a case of TFEB-translocated andamplified RCC with multiple lymph node metastases. We controlled the disease for 52 months by multimodal therapy including surgeries, a VEGFR inhibitor, and radiation therapy.
MiT family translocation RCC is a newly introduced category of renal neoplasia in the 2016 WHO classification. 1 TFEB translocation RCC is a type of MiT family translocation RCC; it harbors gene fusions involving TFEB, resulting in overexpression of native TFEB. TFEB translocation RCC is rare (0.02% of all renal carcinomas). The mean age of affected patients is 34 years, with a wide reported range of 3 to 77 years. There is no remarkable sex predominance (female:male ratio, 0.75:1.00). 3 Most cases of TFEB translocation RCC reportedly have an indolent clinical course. 4 The TFEB is located in the short arm of chromosome 6, specifically in the 6p21-p23 region. 5 The most commonly reported fusion partner for the TFEB is the MALAT1 (81%), 4 and more recent studies have revealed ACTB, NEAT1, 6 COL21A1, and CADM2 7 as rarer fusion partners. In the present case, the fusion partner and the exact fusion point could have been identified by reversetranscription polymerase chain reaction. Unfortunately, we did not store frozen specimens. The MiT family of transcription factors is involved in melanocyte and osteoclast differentiation. 8 Immunohistochemical stains for melanocyte-related antigens and osteoclast markers play supportive roles in the diagnosis of MiT family translocation RCCs. 9 TFEB-amplified RCC was first included in the "TFEBaltered RCCs" group in the 2022 WHO classification. 1 This type of RCC is extremely rare, with only approximately 60 reported cases worldwide to date. 9 TFEB-amplified RCC differs from unamplified TFEB translocation RCC in several ways. 2 First, the mean age at presentation is 65 years, which is higher than that at the presentation of TFEB translocation RCC. Second, its morphology is usually highly malignant in terms of the International Society of Urologic Pathologists/ WHO 2016 nucleolar grade. Finally, patients with TFEB- amplified RCC typically have an aggressive clinical course. Concurrent VEGFA amplification has been reported in TFEBamplified RCC. 2,10 In addition, frequent expression of programmed death-1 ligand 1 was described in both TFEB translocation RCC 6 and TFEB-amplified RCC. 11 In the present case, not only TFEB but also VEGFA was amplified, as in the previously reported cases. VEGFA is immediately adjacent to TFEB at 6p21.1. Given the proximity of these two genes, the VEGFA status has been investigated in TFEB-amplified RCC. 12 In a study of RCC with TFEB gene alternation, Cali o et al. 10 stated that VEGFA amplification is considered to lead to overexpression of VEGF and enhancement of angiogenesis and that VEGF is a potential therapeutic target for TFEB-amplified RCC. Likewise, in the present case, we assumed that VEGF was overexpressed. We hypothesized that the good long-term response to the VEGFR inhibitor was due to VEGF overexpression. Further investigations are warranted to determine whether patients with TFEB-amplified RCC are good responders to VEGFR target therapy.

Conclusion
We have herein presented a case of TFEB-translocated andamplified RCC with multinodal metastases that were controlled for 52 months by multimodal treatment. The good response to the VEGFR inhibitor may have been due to the concurrent amplification of VEGFA and subsequent VEGF overexpression.