Computed tomography of multilocular cystic nephroma.

Three cases of multilocular cystic nephroma (MNC) tht were demonstrated by computed tomography (CT) are described. In two cases a correct preoperative diagnosis was made. In the third case, however, the mass did not fit exactly the histologic criteria for MCN. MCN appears on CT scans as a well-marginated, rounded, or polycyclic cortical mass that extends beyond the normal renal outline. This mass contains cysts that vary in size and number. It may be a cluster of a few large cysts with thick walls and septa, or it may be a denser mass composed of tiny cysts. This CT pattern is suggestive of MCN, but is not sufficient to obviate surgery. However, as part of a complete preoperative evaluation including arteriography, CT provides information that may be valuable in limiting the surgical procedure, perhaps avoiding unnecessary nephrectomy.