Case of the month: June 1998--2 year old boy with lumbosacral mass.

We report the case of a boy aged 2 years with spina bifida and a lipomyelomeningocele which contained ectopic immature renal tissue. He presented with a swelling over the lumbosacral region, incontinence, and bilateral leg weakness. Histopathologic examination revealed adipose tissue in which a focus of fibrous tissue contained neuroglial elements, striated muscle fibres and clusters of glomeruloid structures surrounded by immature tubules. The differential diagnosis of teratoma and lipomyelomeningocele with nephrogenic rests is discussed with reference to possible pathogenesis.