Imaging findings in fumarate hydratase-deficient renal cell carcinoma: a case series of 11 patients.2022 · PURPOSE: Fumarate hydratase (FH)-deficient renal cell carcinoma (RCC) is a rare and aggressive RCC subtype defined in the 2022 WHO classification. This study aimed to describe its imaging and clinicopathological features. METHODS: A retrospective analysis was conducted on 11 patients (12 tumors) diagnosed with FH-deficient RCC between 2015 and 2024 across multiple institutions. Clinical data, imaging findings (CT, MRI, [18F] fluorodeoxyglucose (FDG) -PET/CT), and histopathological results were reviewed. RESULTS: The median age at diagnosis was 54 years (range: 35-81), with a male predominance (64%). At presentation, distant metastases were observed in 27% of patients. Based on contrast-enhanced CT findings, tumors were morphologically classified into three types: cystic-predominant (n = 5), solid-predominant (n = 4), and purely solid (n = 3). The dynamic enhancement pattern of the solid components showed progressive enhancement in 54.5% and mild corticomedullary enhancement with delayed washout in 45.5%, suggesting vascular heterogeneity. MRI showed high signal intensity of cystic components on both T1WI and T2WI, suggestive of hemorrhage. Solid components exhibited restricted diffusion on DWI in all cases, with a median ADC value of 0.88 (range: 0.77-1.18) × 10⁻³ mm²/s. On FDG-PET/CT, solid components demonstrated elevated FDG uptake (median SUVmax: 7.25; range: 6.81-10.10). Among nine cases with available follow-up data, three (33%) developed recurrence within two years after surgery. CONCLUSION: FH-deficient RCC has a high risk of metastasis and recurrence, requiring strict follow-up. Although definitive diagnosis relies on immunohistochemistry, imaging features-such as mixed cystic-solid morphology, hemorrhagic cysts, and, compared with clear cell RCC, lower enhancement, restricted diffusion, and higher FDG uptake-may serve as important diagnostic clues that facilitate accurate pathological diagnosis and management.
Role of 18F-FDG-PET in renal tumors: insights from WHO 2022 classification.2022 · The objective of this article is to provide a comprehensive overview of the imaging characteristics of various renal cell tumors using 18F-fluorodeoxyglucose (FDG)-positron emission tomography (PET), based on the latest WHO-2022 classification. Due to the physiological accumulation of FDG in the kidneys, the clinical utility of FDG-PET in the evaluation of renal tumors has traditionally been considered limited. However, recent studies have re-evaluated its potential value. FDG-PET has demonstrated particular utility in detecting metastases and postoperative recurrence of renal cell carcinoma (RCC), as well as in identifying RCC in patients with chronic kidney failure, where FDG excretion into the urinary tract is reduced. Renal tumors are occasionally detected incidentally on FDG-PET, and FDG uptake varies depending on the tumor subtype. Therefore, a comprehensive understanding of these imaging characteristics is clinically important, as it may serve as a valuable guide for subsequent diagnostic evaluations. Furthermore, recent advancements in the development of novel PET tracers hold promise for future applications in the imaging of renal tumors. We believe that the insights gained from this study will contribute to routine diagnostic practice and the planning of future research.
