Figure 2. Histological appearances of the cyst wall. The internal lining of the cyst is columnar and pseudostratified epithelium (thick arrow) residing on a thin layer of collagen. The outer surface of the cyst wall is covered by arachnoidal cells (fine arrow). Higher magnification shows the ciliated, columnar epithelium (inset A, arrow shows cilia). There is a strong epithelial membrane antigen (EMA) immunoreactivity of the internal epithelial lining (inset B). Haematoxylin and eosin (H&E) stain (main picture and inset A), EMA immunohistochemistry (inset B). Original magnifications 50 x , 630 x (inset A), 200 x (inset B).