Discussion
MiT-family translocation RCC has TFE3 on chromosome Xp11.2 and the transcription factor EB gene on chromosome 6p21 as the major translocated genes. It was also reported that approximately 15% of these cases have a history of chemotherapy in childhood.1 Our case was suspected of being associated with prior chemoradiotherapy. SMN after nephroblastoma treatment is widely known; for example, brain tumors, single retinoblastoma, and basal cell carcinoma. RCC is relatively rare as a SMN after nephroblastoma treatment, and only 4 of 13,351 patients were found to have RCC in a recent multi-institutional report.2 In our review of 11 previously reported cases of secondary RCC after nephroblastoma treatment as well as our own study (Table 1), only 2 cases, including our own study, were diagnosed as translocation RCC.1 Eight cases were clear cell RCC3–9, one case was papillary cell RCC10, and one case had an unspecified histologic type. Our review included only two cases of translocation RCC, although this number might be underestimated. This is because translocation RCC was first classified in the 2004 World Health Organization classification of renal tumors; prior cases were impossible to diagnose, and diagnosis of TFE3 translocation RCC may be inaccurate in facilities that cannot perform the TFE3 break-apart FISH technique.11
The appropriate course of action for this clinical case was difficult to determine because of suspected metastasis. For a single metastatic RCC suspected in the left eighth rib, cytoreductive partial nephrectomy and resection of the metastases, or systemic therapy after tissue diagnosis by renal biopsy, are viable treatment options. However, given that this is a single kidney case, needle renal biopsy is a high-risk option. Additionally, there is insufficient evidence supporting the efficacy of immune checkpoint inhibitors or tyrosine kinase inhibitors for metastatic translocation RCC. In our review, the longest recurrence-free period of RCC after surgery was 22 months.4Considering the need to preserve renal function, enhance the precision and safety of histological analysis, and ensure curative potential, partial nephrectomy was deemed the preferable option.
In our review (Table 1), six cases underwent partial nephrectomy as surgical treatment. No reports of severe acute renal failure were observed during the operative period. These findings suggest that partial nephrectomy is also valuable in treating secondary RCC after nephroblastoma treatment with regards to preservation of renal function.