Brain Pathology Case of the Month - June 1998




The differential diagnosis of this pathology which contains tissues arising from (neuro)ectoderm and mesoderm is teratoma and lipomyelomeningocele with nephrogenic rests. We favor the latter because renal tissue is both very rare in teratomas and the only unexpected element in this lesion which otherwise contains heterotopic tissues that are recognized components of lipomas in association with neural tube defects (2). Further support for this choice is provided by the finding that nearly all sacrococcygeal teratomas in infants over 4 months old are malignant (6). However, the frequent presence of multiple tissues in midline lipomas attests to the indistinct borderline between malformations (including hamartomas) and teratomas in the lumbosacral region (2,3,13).

Benign ectopic immature renal tissue is a rare finding, and the combination of immature or dysplastic renal tissue and hamartomas or choristomas of the lumbosacral region has been documented only a few times (1,4,10). One of these four cases was associated with spina bifida, and one with myelomeningocele. None was associated with malignant behavior. However, cases of Wilms' tumor that arise in the lumbosacral region in association with spina bifida and pre-existent masses have been described (9,12,14).

The presence of nephrogenic rests in a lipomyelomeningocele might be explained if neural tube defects interfere with the migration of renal tissue. In support of this is the frequent association of neural tube defects with renal anomalies (2). Alternatively, aberrant induction of renal tissue might explain this lesion. Normal development of the nephron is induced in metanephric blastema by the ureteric bud; however, central nervous system tissue is capable of inducing nephron formation in cultured tissue taken from undifferentiated Wilms' tumor (5), and of inducing tubules in metanephric mesenchyme (8). The expression of nerve growth factor receptor in developing nephrogenic tissue is required for the formation of the kidney tubules (11).


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  2. Bale PM (1984) Sacrococcygeal developmental abnormalities and tumors in children. Perspect Pediatr Pathol 1:9-56
  3. Black SPW, German WJ (1950) Four congenital tumors found at operation within the vertebral canal. J Neurosurg 7:49-61
  4. Cozzuto C, Stracca-Parsa V, Salano F (1983) Renal dysplasia of the sacral region: metanephric dysplastic hamartoma of the sacral region. Virchows Arch [Pathol Anat] 402:99-106
  5. Crocker JFS, Vernier RL (1972) Congenital nephroma of infancy: Induction of renal structures by organ culture. J Pediatr 80:69-73
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  7. Gaskill SJ, Kagen-Hallett K, Marlin AE (1988) Diastematomyelia associated with ectopic renal tissue. Pediatr Neurosci 14:108-111
  8. Gorbstein C (1955) Inductive interaction in the development of the mouse metanephros. J Exp Zool 130:319-339
  9. Mickle JP, McLennan JE (1975) Malignant teratoma arising within a lipomeningocele: Case report. J Neurosurg 43:761-763
  10. Posalaky Z, Drake RM, Mawk JR, Franciosi RA, Spencer BH, Athinarayanan PR, Baker TA, Viring N (1982) Ectopic immature renal tissue over the dorsum of lumbar and sacral area in two infants. Pediatrics 69:336-339
  11. Sariola H, Saarma M, Sainio K, Arumae U, Palgi J, Vaahtokari A, Thesleff I, Karavanov A (1991) Dependence of kidney morphogenesis on the expression of nerve growth factor receptor. Science 254:571-573
  12. Tebbi K, Ragab AH, Ternberg JL, Vietti TJ (1974) An extrarenal Wilms' tumour arising from a sacrococcygeal teratoma. Clin Pediatr 13:1019-1021
  13. Tibbs PA, James HE, Rorke LB, Schut L, Bruce DA (1976) Midline hamartomas masquerading as meningomyeloceles or teratomas in the newborn infant. J Pediatr 89:928-933
  14. Ward SP, Dehner LP (1974) Sacrococcygeal teratoma with nephroblastema (Wilms' tumor): a variant of extragonadal teratoma in childhood. Cancer 33:1355-1363

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