Diagnostic MRI characteristics of pediatric clear cell sarcoma of the kidney and rhabdoid tumor of the kidney: A retrospective multi-center SIOP-RTSG Radiology panel study

Diagnostic magnetic resonance imaging characteristics of congenital mesoblastic nephroma: a retrospective multi-center International Society of Pediatric Oncology-Renal Tumor Study Group (SIOP-RTSG) radiology panel study

“…We showed ADC values for all subtypes to be approximately the same, with overall means ranging from 1.05 to 1.10×10 −3 mm 2 /s, indicating moderate diffusion restriction in most tumors. ADC values around this range have also been described for clear cell sarcoma of the kidney, as well as stromal type Wilms tumor, whereas in general, more aggressive Wilms tumor subtypes show a higher diffusion restriction [ 44 , 55 , 56 ].…”

“…T2W isointensity particularly, appears to be potentially discriminating in the differentiation of congenital mesoblastic nephroma from the often T2W hyperintense Wilms tumor. Nonetheless, while the classic type congenital mesoblastic nephroma often appears homogeneous on imaging, the cellular and mixed type show more overlapping imaging MRI characteristics with malignant pediatric renal tumors in the same age range, such as Wilms tumor, rhabdoid tumor of the kidney, and clear cell sarcoma of the kidney [ 2 , 3 , 6 , 8 , 11 , 21 , 31 , 37 , 44 ].…”

“…Nevertheless, Wilms tumors are often described as T2W hyperintense, which might indicate T2W isointensity as slightly discriminative for congenital mesoblastic nephroma in general [ 21 , 22 , 24 , 53 ]. Rhabdoid tumors of the kidney are reported to be small, mainly T2W hypointense and often show infiltrative and aggressive features, potentially discriminating them from congenital mesoblastic nephroma as well as from Wilms tumors [ 44 , 54 ]. Finally, no additional potentially discriminative MRI characteristics were identified for mixed type congenital mesoblastic nephroma, concerning both differentiation from the classic and cellular type and from other renal tumor types.…”

“…Our study has several limitations, predominantly related to its international setting and retrospective nature. While this could lead to potential information bias and variability, there was excellent interrater agreement among the included radiologists, who are experts in the field of imaging of pediatric renal tumors [ 44 ]. Also, the design of this study and related inclusion in different SIOP-RTSG protocols over the past decades affects the extent of national registration and center-specific choice of cross-sectional imaging modalities, which may have led to registration bias, potentially resulting in a disproportionate number of included patients per country, nonetheless also taking into consideration differences in population.…”

“…Each of the five national review radiologists assessed their own national congenital mesoblastic nephroma cases through a case report form (CRF), which was validated through an extensive interrater agreement study (median observed agreement of 77.0% (range 57.3–94.5%) among five raters) in a prior publication, showing satisfactory results [ 44 ]. This way, all included cases could be assessed by the individual national radiologist, without obligation for two observers per patient and without need for regulatory data sharing agreements.…”