• A cyst may or may not manifest as a swelling, depending on the size; the tooth may or may not be painful; a well-circumscribed radiolucency is present at the apex (apical radicular) or on the side (lateral radicular) of a nonvital tooth; there may have been prior root canal (endodontic) therapy (Fig. 14-4, A and B).

• Residual cyst refers to any odontogenic cyst in the alveolar bone where a tooth had been extracted and is most often a residual apical radicular cyst (see Fig. 14-4, C)

• 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).

• Any inflamed intraosseous, odontogenic, or other cyst may appear similar.

• If epithelium is not present, the diagnosis is periapical granuloma (Fig. 14-14); sheets of plasma cells are common in periapical granulomas, and they should not be overdiagnosed as plasmacytomas (Fig. 14-15).

• Periapical scar shows only fibrosis, sometimes with inflammation (Fig. 14-16).

• Chronic active periodontal disease appears similar histologically, but clinically, the tooth is surrounded by a periradicular radiolucency; disease starts either from an apical radicular cyst that grows very large and combines with an overlying periodontal bone defect or from periodontal disease starting from the surface of the bone and extending downwards to encompass the entire tooth.

• Enucleation or curettage with apicoectomy (excision of the root tip) is curative.

• Children in the first decade (mean age of 7 years); 38% bilateral

• Swelling and pain in the area of the first permanent molar; radiolucency around a vital first molar that extends from the furcation (where roots diverge) to the apex of the tooth causing tilting of the roots lingually (best seen on occlusal radiograph); periosteal reaction usually present (Fig. 14-17)

• Similar to radicular cyst with proliferative epithelium and acute and chronic inflammation

• Some clinicians consider the bucc/>