Congenital mesoblastic nephroma, although rare, represents the most common renal neoplasm diagnosed in the early postnatal period ( 1 3 ) . More than 70 cases of this benign tumor have been reported (4); however, there are few descriptions in the radiology literature (5-9).
Previous reports have emphasized the noncystic nature of this neoplasm (1,3). The present case, however, demonstrated a multicystic component at sonographic and subsequent pathologic examination. To our knowledge this is the first description of the ultrasonic appearance of a cystic form of mesoblastic nephroma.
CASE REPORT
A 5-wk-old white female was evaluated for increasing abdominal girth and palpable right flank mass. Initial plain-film radiography showed a large, noncalcified soft-tissue mass in the right side of the abdomen with marked displacement of bowel loops across the midline to the left. An excretory urogram revealed a normal left kidney. The right kidney demonstrated moderate excretion but was markedly displaced anteriorly and to the left (Fig. and). At sonography, the mass was shown to consist of a posterior, central echogenic region surrounded anteriorly and peripherally by multiple contiguous cysts with thin intervening septa (Fig. and). The posterior location of the solid component of the mass suggested origination from the midretroperitoneum.
At laparotomy, a multicystic right renal mass was found and a right nephrectomy was per-From the Departments of Radiology and Pediatrics,