Endodermal Cyst Ventral to the Lower Brain Stem-Case Report-

Abstract

A 28-year-old woman presented with a rare case of endodermal cyst located ventral to the lower brain stem manifesting as recurrent aseptic meningitis. Computed tomography and magnetic resonance imaging demonstrated a cystic mass located ventral to the lower brain stem and extending from the prepontine to the upper cervical (C-2) cistern. The lesion was totally removed through a retrosigmoid craniotomy and C1-2 hemilaminectomy. Histological and immunohistochemical examination showed the cyst was derived from the endoderm. The histological diagnosis was endodermal cyst. Early diagnosis and surgical removal are important for patients with these cysts.

Surgical Strategy for Intracranial Endodermal Cyst-Two Case Reports-

“…4,11) Neuroepithelial cyst is considered to originate from the heterotopic nests of the ectodermal cells, such as primitive ependyma or choroid plexus, whereas endodermal cyst is presumed to associate with persistence of the neurenteric canal. In the third week of embryogenesis, the notochordal canal is formed in the embryonic mesoderm, which is interposed between the amniotic cavity and the yolk sac.…”

“…20) Intracranial endodermal cyst is usually located in the midline or paramidline of the posterior fossa. 2,11) The intracranial cyst is postulated to arise from the aberrant cells of the foregut or respiratory buds, in the brain vesicle, through the transient neurenteric canal. 2,4,9,17) Diagnosis of endodermal cyst is based on the histological findings.…”

“…The wall of the cyst consists of a single layer of ciliated or nonciliated, columnar or cuboidal epithelium, with a basement membrane. 3,4,11) Immunohistochemical examinations of the epithelium will identify epithelial markers such as cytokeratin and EMA as positive, whereas ectodermal markers such as GFAP and S-100 protein are negative. 3,4,11) Epithelial cells sometimes have secretory granules which are positively stained for Alcian blue.…”

“…3,4,11) Immunohistochemical examinations of the epithelium will identify epithelial markers such as cytokeratin and EMA as positive, whereas ectodermal markers such as GFAP and S-100 protein are negative. 3,4,11) Epithelial cells sometimes have secretory granules which are positively stained for Alcian blue. 3,4) Additional examinations in our cases were positive for cytokeratin 7, but negative for cytokeratin 20 or CEA.…”

“…The cyst contents usually appear as hypo-, iso-, or hyperintensity on T 1 -and T 2 -weighted MR images, probably based on the presence of protein, hemorrhage, and fat. 3,4,11,16,20) Opaque or whitish, thin cyst walls are surgically explored in most cases, but the cyst contents may be opaque, 9) white, 1,12,16) straw, 5) or green 2) in color, and with creamy, 11,16,21) gelatinous, 12) or mucoid 2,4,14,22) consistency. FLAIR MR imaging can differentiate endodermal cyst from arachnoid cyst.…”