Ectopic neural tissue as an unusual cause of a retroperitoneal tumor

In a 3-year-old boy an abdominal mass was palpated by chance, which consisted of cystic and solid structures and was shown on ultrasound scan and computed tomography to be located retroperitoneally. Intraoperatively, the cystic tumor contained clear, yellowish fluid and had a stalk leading to the interspinal space between L2 and L3. However, no signs of dysraphism, were found. Neuropathologic examination surprisingly showed non-neoplastic ectopic neural tissue, which has never been recorded at this extraspinal site before.