Pulmonary glial heterotopia in a monoamniotic twin.

Brain heterotopia in the lungs is rare, but when it occurs in an otherwise healthy newborn, it presents a difficult diagnostic problem and uncertain pathophysiology. We report on a 2-week-old premature infant who presented with respiratory distress and widespread cystic lung changes identified by chest imaging studies. Autopsy demonstrated that the cyst walls were composed of well-differentiated neuroglial tissue, which was confirmed by immunohistochemistry. The cysts were partially lined by bronchial epithelium and contained keratinous debris. For the first time, we demonstrate that the debris stain for human chorionic gonadotropin, compatible with aspirated amnion. There were no other congenital abnormalities. Her monoamniotic twin was anencephalic and died at birth. Although the etiology of glial heterotopia in the lungs is unknown, the majority of cases are associated with anencephalic newborns. Some authors postulated that this heterotopia may therefore be a consequence of fetal aspiration of brain tissue. Other possibilities include glial predominant teratomas, hamartomatous malformations, and abnormal neural crest migration. Our review of the 21 cases reported over the past century suggests that in utero aspiration of glial cells, or abnormal neural crest migration, are the most likely explanations for this rare and fatal disease.