Odontogenic cysts, odontogenic tumors, fibroosseous, and giant cell lesions of the jaws.

Odontogenic cysts that can be problematic because of recurrence and/or aggressive growth include odontogenic keratocyst (OKC), calcifying odontogenic cyst, and the recently described glandular odontogenic cyst. The OKC has significant growth capacity and recurrence potential and is occasionally indicative of the nevoid basal cell carcinoma syndrome. There is also an orthokeratinized variant, the orthokeratinized odontogenic cyst, which is less aggressive and is not syndrome associated. Ghost cell keratinization, which typifies the calcifying odontogenic cyst, can be seen in solid lesions that have now been designated odontogenic ghost cell tumor. The glandular odontogenic cyst contains mucous cells and ductlike structures that may mimic central mucoepidermoid carcinoma. Several odontogenic tumors may provide diagnostic challenges, particularly the cystic ameloblastoma. Identification of this frequently underdiagnosed cystic tumor often comes after one or more recurrences and a destructive course. Other difficult lesions include malignant ameloblastomas, calcifying epithelial odontogenic tumor, squamous odontogenic tumor, and clear-cell odontogenic tumor. Histologic identification of myxofibrous lesions of the jaws (odontogenic myxoma, odontogenic fibroma, desmoplastic fibroma) is necessary to avoid the diagnostic pitfall of overdiagnosis of similar-appearing follicular sacs and dental pulps. Fibroosseous lesions of the jaws show considerable microscopic overlap and include fibrous dysplasia, ossifying fibroma, periapical cementoosseous dysplasia, and low-grade chronic osteomyelitis. The term fibrous dysplasia is probably overused in general practice and should be reserved for the rare lesion that presents as a large, expansile, diffuse opacity of children and young adults. The need to use clinicopathologic correlation in assessing these lesions is of particular importance. Central giant cell granuloma is a relatively common jaw lesion of young adults that has an unpredictable behavior. Microscopic diagnosis is relatively straightforward; however, this lesion continues to be somewhat controversial because of its disputed classification (reactive versus neoplastic) and because of its management (surgical versus. medical). Its relationship to giant cell tumor of long bone remains undetermined.