Figure 7. Structure of an apical pocket cyst. Axial sections passing peripheral to the root canal (a,b) give the false impression of the presence of a cyst lumen (LU) completely enclosed in epithelium. Sequential section (c,d) passing through the axial plane of the root canal (RC) clearly reveals the continuity of the cystic lumen (LU) with the root canal (RC). Note the pouch-like lumen (LU) of the pocket cyst with the epithelium (EP), forming a collar at the root apex. Magnifications: (a,b,c) 5x; (d) 132x. (Adapted from Nair, 1995.)