RESUMO
Benign mucinous cystadenomas MCA are rare benign neoplasms in the pediatric age group. Only 19 cases have been described before, and they often present as large abdominal masses. We present a 12-year-old patient that had a huge mass arising from the left ovary causing bilateral hydronephrosis and renal insufficiency. The final pathology revealed a benign MCA. Patients with mucinous tumors usually present late, this may lead to renal insufficiency secondary to urinary outflow obstruction. Unilateral salpingo-oophorectomy is usually sufficient treatment for these cases. The diagnosis of MCA should be considered in children who present with huge pelvi-abdominal masses. Early recognition and intervention are necessary to avoid potential complications