Microscopic features of the lateral periodontal cyst.

The lateral periodontal cyst is of developmental odontogenic origin and must be differentiated from the gingival cyst of adults, a primordial cyst in a lateral periodontal position, and a cyst of inflammatory origin. This paper is based on a histologic study of five cases. Four were in the mandibular premolar region and one in the lateral incisor-canine region of the maxilla. The cysts are lined by a thin non-keratinized epithelium which resembles the reduced enamel epithelium. Many of them arecharacterized by the presence of localized plaque-like thickenings of their epithelial linings, consisting of fusiform or large swollen, edematous cells. These epithelial thickenings appear to result from a localized proiferation of basal cells. The lateral periodontal cyst may arise initially as a dentigerous cyst which develops by expansion of the follicle along the lateral surface of the crown and comes to lie on the lateral aspect of the root if tooth eruption is normal. Alternatively, it may arise from the cell rests of Malassez.