Uroradiology & genital male imagingCase Type
Brecht Van Berkel, MD; Geert Verswijvel, MDPatient
40 years, female
A 40-year-old female presented with recurring episodes of vomiting and diarrhoea for the past 2 months. The patient had no significant medical history. A mass lesion was found in the left kidney, nephrectomy was performed.
Ultrasound showed a hypoechoic mass in the lower pole of the left kidney, hypovascular on colour-coded Doppler (CCD) (Fig 1). MRI was performed on a 1.5 T. The mass had a heterogeneous signal intensity (SI) on T2-weighted images with a predominantly low T2 signal and areas of patchy high SI in the periphery of the tumor (Fig 2a and b). The lesion was iso- to low in SI on T1-weighted images compared to renal cortex (Fig 3). Opposed phase imaging did not show intralesional signal drop. The tumour signal was high on diffusion-weighted images (DWI, b=1000) and low on the apparent diffusion coefficient (ADC) map (Fig 4). Contrast-enhanced multiphase 3D volumetric interpolated T1 (VIBE) was performed and demonstrated moderate enhancement of the lesion in the corticomedullary phase (lower in SI to the renal cortex) and iso- to lower enhancement in the renal parenchymal phase (Fig 5a and b).
Pathology revealed XP11.2 translocation RCC.
Renal cell carcinoma (RCC) associated with Xp11.2 translocation/TFE3 gene fusion (Xp11.2/TFE RCC) is a rare subtype of RCC primarily affecting children and young adults.  This subtype accounts for approximately 0.5 % of adult RCCs compared to 20 % of RCCs in young people.  Since 2004 it has been classified by the World Health Organization (WHO) as a separate entity with unique pathologic characteristics and biological behaviour. Xp11.2/TFE RCC originates from the renal medulla, whereas a clear cell RCC originates from the renal cortex.  The lesion typically presents as an asymptomatic renal mass, often as an incidental finding on imaging modalities. If symptomatic, macroscopic hematuria, flank pain and a palpable mass have been reported.  For the diagnostic work-up CT and MRI are valuable imaging modalities. Differentiation from other primary renal tumours can be difficult, especially with the papillary subtype.  Compared to papillary RCC, Xp11.2/TFE RCC is reported to have a greater size, have more intralesional cystic change or necrosis, frequently contains calcification and/or be hyperdense to renal parenchyma on unenhanced imaging. Just like papillary RCC, Xp11.2/TFE RCC is hypovascular in the corticomedullary phase after contrast injection. A recent retrospective study with 16 patients showed that enhancement of the lesion was less than renal cortex on all phases and higher than the medulla in arterial and corticomedullary phase and lower to medulla in the delayed phase. [5,6] MRI-findings include hypointensity on T2-weighted images (T2WI), hyper- to isointense on T1-weighted images (T1WI) to renal parenchyma and hyperintensity on DWI with low ADC.  Xp11.2/TFE RCCs with metastases were more likely to show an irregular shape, an incomplete capsule, and a solid-cystic pattern with haemorrhage than the subgroup without metastases.  Adult Xp11.2/TFE RCC shows high invasiveness with rapid disease progression. The prognosis for adult Xp11.2/TFE RCC is much poorer than pediatric Xp11.2/TFE RCC.  Radical nephrectomy remains the most common strategy to treat Xp11.2/TFE RCC, since the treatment with chemotherapy and radiotherapy proved to be unsuccessful. Nephron-sparing surgery (NSS) in Xp11.2/TFE RCC is rarely reported, although it has been confirmed safe and effective in conventional RCCs. 
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