Terminal myelocystocele: important differential diagnosis in the prenatal assessment of spina bifida.

The most common lumbosacral mass of a fetus is a meningomyelocele that is not covered by skin; however, skin-covered lesions do occur, and they often have a quite different clinical cause and outcome. It is often difficult to make this differentiation on ultrasonography; when a skin-covered mass in the lumbosacral region is encountered, the following differential diagnoses should be considered. The most common skin-covered lesion is the lumbosacral lipoma (i.e., lipomeningocele or lipoma), followed by the teratoma, hamartoma, and the other rarer tumors and mass lesions.1 The TM appears as a skin-covered mass in the lumbosacral region, sometimes associated with urologic and gastrointestinal tract abnormalities.2,3 Although TMs may appear similar to myelomeningoceles on prenatal ultrasonography, it is of the utmost importance to distinguish them, as the outcome and prognosis and thus the prenatal counseling will be quite different.4 In addition to the presumed difference in pathophysiology, there is no familial occurrence and therefore no genetic predisposition for future offspring.2,4,5 We present a patient with TM and describe the prenatal findings, postnatal studies, and clinical course.