[MRI-morphology and staging of congenital mesoblastic nephroma: evaluation of a collection with 20 patients].
OBJECTIVE
To differentiate classic and cellular type of congenital mesoblastic nephroma (CMN) in MRI and to evaluate MRI for staging according to the Societe Internationale de Oncologie Pediatrique (SIOP).


METHODS
MRI examinations of 20 children with CMN (age 1st to 16th months, classic type n = 11, cellular type n = 7, mixed type n = 2) were analyzed retrospectively. Cysts, necrosis, hemmorhage in the tumor, signal intensity, tumor structure, thrombosis and dilatation of renal vein, crossing of the body midline, peripheral contrast-enhancement, tumor volume and existence of a tumor pseudocapsule in contrast to the residual kidney were described. The radiologic stage was compared with the histopathologic stage (infiltration of perirenal fat and infiltration of the renal sinus).


RESULTS
Tumors of the classic type (mean volume 67.9 ml) had necrosis in 1 case, crossed the midline in 1 case, had no cysts or bleeding, and had a peripheral contrast-enhancement in 1 case, and were heterogeneous in 9 cases. The cellular type (mean volume 302.8 ml) had tumor necrosis in 6 cases, bleeding in 3 cases, cysts in 3 cases, crossed the midline in 4 cases, and peripheral contrast enhancement in 2 cases, and was predominantly heterogeneous. Mixed tumor types (7 ml and 202 ml) had tumor necrosis in 1 case and crossed the midline in 1 case, a peripheral contrast enhancement in 2 cases and a homogenous structure in 1 case. The signal intensity in T1 w and T2 w images was not specific. The renal vein was inconspicuous in all children. The evaluation of the infiltration in perirenal fatty tissue was true positive in 1 case, true negative in 10 cases, false negative in 4 cases and false positive in 5 cases. The infiltration of the renal hilus was true positive in 10 children, false positive in 8 cases and true negative in 2 cases.


CONCLUSIONS
A typical finding of CMN in MRI is a heterogeneous tumor without demarcation from the rest of the kidney parenchyma by a pseudocapsule. The cellular type of CMN tends to have a higher tumor volume and shows more necrosis, bleeding and cysts than the classic type in MRI. A peripheral contrast-enhancement in MRI is not characteristic for any type of CMN. Local tumor staging is not possible with MRI.
Schenk
J P
JP
Abt. Päd. Radiologie Universitätsklinik Heidelberg, Im Neuenheimer Feld 153, 69120 Heidelberg. jens-peter_schenk@med.uni-heidelberg.de
Schrader
C
C
Furtwängler
R
R
Ko
H S
HS
Leuschner
I
I
Graf
N
N
Troeger
J
J
D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007680:Kidney Neoplasms / Q000145:classification / Q000151:congenital* / Q000473:pathology*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D009367:Neoplasm Staging / Q000379:methods*; D018201:Nephroma, Mesoblastic / Q000145:classification / Q000151:congenital* / Q000473:pathology*; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012680:Sensitivity and Specificity