Multiphasic contrast-enhanced CT and MRI findings of adult mesoblastic nephroma: A report of two cases
A 46-year-old man with a history of intermittent gross hematuria for 1 year was admitted to our hospital. Ultrasound examination of the kidneys detected a 12-cm, well-delineated, partly cystic mass herniating into the right renal pelvis (not shown). A CT scan revealed a well-defined, solid and cystic, mixed attenuation renal mass bulging into the renal pelvis []. The mass was ovoid and mainly solid, showing heterogeneous attenuation with moderate prolonged enhancement on CMP and NP [Figure and , respectively]. The highest CT value of the tumor was 46 HU, 120HU and 135HU on plain scan, CMP and NP, respectively. There was no enhancement seen in the hypoattenuation area of the mass corresponding to the cystic area described on ultrasound. The tumor was bulging out of the renal parenchyma without peri-nephric infiltration. A radical nephrectomy of the right kidney was performed because of the diagnosis of renal cell carcinoma on CT scan. Microscopically, the tumor was composed of spindle-shaped cells showing both fibroblastic and muscle differentiation admixed with entrapped clusters of tubular epithelium. The epithelial component showed large foci of proliferating tubules. There was no cytologic atypia in either the mesenchymal or the epithelial component. On histological examination, the tumor was composed mainly of proliferating spindle cells, which stained strongly with smooth muscle actin, with variable cellularity and epithelial tubular cells scattered amid the spindle cells []. Although the tumor was well circumscribed, it lacked a true capsule. The patient was free of disease on the 2-year follow-up examination.