CONGENITAL MESOBLASTIC NEPHROMA IN A CHILD WITH THE BECKWITH-WIEDEMANN SYNDROME

Abstract

To our knowledge we report the first known case of congenital mesoblastic nephroma in an infant with the Beckwith-Wiedemann syndrome. The renal tumor classically associated with the Beckwith-Wiedemann syndrome is Wilms tumor with an overall risk of occurrence of 3 to 5%.1 However, congenital mesoblastic nephroma is the most common renal tumor of infancy, with 60% of cases presenting within the first 3 months of life and 90% presenting during the first year of life.' CASE REPORT M. M. was first seen at 4 weeks of age for a large umbilical hernia with drainage. Abdominal ultrasound revealed a possible urachal cyst and normal kidneys, but no other abnormality. A voiding cystourethrogram was normal. Genetic service evaluation for large body size (more than 90th percentile), left lower limb hemihypertrophy, asymmetrical macroglossia, posterior helical indentations of the ear pinna, umbilical anomaly and hypoglycemia in the first days of life resulted in a clinical diagnosis of Beckwith-Wiedemann syndrome. A followup abdominal ultrasound and subsequent computerized tomography performed at 8 weeks of life showed resolution of the urachal anomaly, but the development of a new 2 x 3 cm. solid mass in the lower pole of the left kidney. Further studies for a possible Wilms tumor included a chest computerized tomography which revealed a 2 mm. nodule in the parenchyma of the right lung. The patient underwent a biopsy of the lung nodule that revealed an unremarkable lymph node. A firm pale mass in the lower pole of the left kidney, a normal contralateral kidney, and no evidence of metastatic disease were found on abdominal exploration. Biopsy of the renal mass showed congenital mesoblastic nephroma characterized by a proliferation of relatively bland spindled cells lacking pleomorphism, no increase in mitotic figures, absence of necrosis and hemorrhage, and the presence of entrapped typical renal