14: Odontogenic Cysts

14 Odontogenic Cysts

The tooth develops from ingrowth of the lining of the primitive stomodeum called the dental lamina. The dental lamina forms tooth buds for the primary and the permanent dentition (Fig. 14-1), and after odontogenesis, remnant epithelium are left behind as rests. The epithelium of odontogenic cysts is thought to arise from stimulation of such residual odontogenic rests (e.g., rests of Serres in the gingiva or rests of Malassez around the tooth roots in the jawbones) (Fig. 14-2).

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FIGURE 14-1 Developing tooth in bell (A) and cap stage (B): A, Ameloblasts; B, Bone; D, Dentin; DF, Dental follicle; DL, Dental lamina; DP, Dental papilla; O, Odontoblasts; SR, Stellate reticulum.

(From Young B, Lowe JS, Stevens A, Heath JW. Wheater’s Functional Histology: A Text and Colour Atlas. 5th ed. Edinburgh, Churchill Livingstone, 2007.)

Odontogenic Cysts

Cystic lesions in the jawbones are either odontogenic or nonodontogenic in their derivation. All odontogenic cysts are inflammatory, developmental, or, less commonly, neoplastic in nature, and the putative epithelium from which they derive may be rests of Malassez, dental lamina rests, reduced enamel epithelium, degenerated enamel organ, or, in rare cases, the epithelium of the surface mucosa (Fig. 14-3). In general, inflammatory odontogenic cysts have proliferative epithelium, and developmental odontogenic cysts have uniformly thin epithelium, although inflammation may lead to epithelial proliferation. The most common cyst is the radicular cyst (>50%), followed by the dentigerous cyst and keratocystic odontogenic tumor (odontogenic keratocyst).

Inflammatory Cysts

Apical and Lateral Radicular Cyst and Periapical Granuloma

A tooth that has caries involving the pulp or that has experienced direct trauma becomes devitalized and may develop a radiolucency at the apex of the root. This may represent an apical radicular cyst, periapical granuloma or scar, or abscess.

Etiopathogenesis and Histopathologic Features

Inflammation from the pulp of necrotic teeth results in proliferation of rests of Malassez, which are remnants of the Hertwig root sheath that helps form the roots of the teeth during odontogenesis.

A radicular cyst is lined by nonkeratinized stratified squamous epithelium that usually proliferates in a plexiform or retiform pattern and exhibits spongiosis and neutrophilic exocytosis; the wall is composed of edematous granulation tissue and often scar tissue, many plasma cells, Russell bodies, lymphocytes, foamy macrophages, and sometimes abscesses are present (Fig. 14-5); curetted specimens may show only granulation tissue with focal lining epithelium (Fig. 14-6).

Hyaline lamellar or globular structures of odontogenic origin (Rushton bodies) may be present within the epithelium (Fig. 14-7); epithelial loss is often associated with cholesterol granulomas.

Foreign material from root canal filling is often seen: gutta percha is yellowish or brownish green, granular, and slightly refractile (Fig. 14-8); cements, in particular epoxy resin (such as AH Plus [Dentsply International, York, Pa], which contains zirconium and iron oxides and calcium tungstate), is usually refractile and crystalline in an eosinophilic background (Fig. 14-9); amalgam tattoo may be present from previous root apex excision (apicoectomy).

Hyaline ring (pulse) granuloma (likely a foreign body reaction to exogenous material) consists of hyalinized rings with central and/or surrounding giant cells; foreign material is sometimes identified (Figs. 14-10 and 14-11).

Radicular cysts from the apices of maxillary molars may be lined by respiratory epithelium (Fig. 14-12); fragments of sinus mucosa, however, signify an oroantral communication and must be reported; fragments of sinus inflammatory polyps may be present—exhibiting few to no mucous glands, eosinophilic coagulum, and eosinophils (Fig. 14-13).

Jan 12, 2015 | Posted by in Oral and Maxillofacial Pathology | Comments Off on 14: Odontogenic Cysts
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