Growing renal mass: mesoblastic nephroma in pregnancy

Case report: A 41-year-old GIII/PI presented for the first time at 30+3 weeks of pregnancy with a newly diagnosed fetal abdominal mass, which hadn't been visible 6 weeks before. At present, sonography reveals a 66 × 56 × 66 mm left renal mass with abundant vascularisation and a macrosomic male fetus. The right kidney is normal in size and shape. The consulted pediatric nephrologist suspects a wilms tumor or a mesoblastic nephroma. Fetal MRT shows a solid mass, 160 ml in volume, the radiologists suspect a mesoblastic nephroma. Because of the maternal pain and respiratory distress of the severe polyhydramnios amnioreduction is performed weekly. During the following three weeks the tumor grows from 160 ml to almost 400 ml. The case is presented to the pediatric oncology board; together, it is decided to allow the pregnancy to go to term despite the fast growth of the tumor. At 34+3 weeks of pregnancy, a spontaneous rupture of membranes occurs 3 days after the last amnioreduction. A cesarean section is performed at the mothers request without complication. The newborn is cyanotic without spontaneous breathing, APGAR 3/5/5, pH 7.31, BE -2.3. Intubation is necessary because of the respiratory failure caused by the big abdominal mass.

On the 3^rd day of life, left radical transperitoneal nephrectomy and staging lymphadenectomy is performed. The operation proves to be difficult to carry out because of the extensive blood vascularisation of the tumor, with great loss of blood. The exchange of 1.5 times the total blood volume is necessary, the newborn receives catecholamine therapy for 2 days. Histology shows a mesoblastic nephroma with tumorfree staging lymph nodes, SIOP Stade II. The newborn is discharged from hospital on day 22 of his life. Follow-up examinations have been uneventful until now.