Clinical Pathologic Conference Cases Presented at the Annual Meeting of the American Academy of Oral and Maxillofacial Pathology, April 25-30, 2014

CLINICAL PATHOLOGIC CONFERENCE CASE 1: A MULTILOCULAR RADIOLUCENCY IN THE POSTERIOR MANDIBLE Colin Eliot, DMD, MS. LCDR, DC, USN, Harvey P. Kessler, DDS, MS, Joint Base Pearl HarborHickam, Hawaii; Professor of Pathology, Department of Diagnostic Sciences, Texas A&M University Baylor College of Dentistry, Dallas, Texas Clinical Presentation: A 22-year-old white female presented to the general dentist with swelling in the right mandible and submandibular area. Clinical examination confirmed expansion of the right mandible. Panoramic radiographic examination revealed a large, well-circumscribed multilocular radiolucency distal to the canine within the body of the mandible (Figure 1). An incision and drainage procedure was performed but was unsuccessful. Aspiration of the lesion also failed to yield output. Differential Diagnosis: Differential diagnosis of a wellcircumscribed, corticated, multilocular radiolucency within the molar region of the mandible should include several categories of pathology, including odontogenic cysts and tumors, non-odontogenic tumors, and other non-neoplastic conditions. A large number of intrabony jaw lesions originate from odontogenic tissues; therefore, odontogenic cysts and tumors should be considered first in a differential diagnosis. Of the odontogenic cysts, odontogenic keratocyst (OKC) would be the most likely in the present case. OKCs affect the mandible approximately 70% of the time and demonstrate a tendency to involve the posterior body of the mandible and the ascending ramus. The majority of OKCs are identified in patients between ages 10 and 40 years. The radiographic presentation of OKCs consists of a well-defined radiolucency, with a smooth and often corticated margin. Larger lesions may present as a multilocular process. In this case, we are not considering the dentigerous cyst, a common odontogenic cyst, because of the absence of an unerupted tooth in the area, and the less common glandular odontogenic cyst because of patient demographic characteristics and biologic behavior. Odontogenic tumors may also present as well-circumscribed, corticated radiolucencies, so a variety of odontogenic neoplasms should be considered in the present case. Given the patient demographic characteristics, ameloblastoma, odontogenic myxoma, and central odontogenic fibroma are considered. Ameloblastoma is the most common clinically significant odontogenic tumor. About 80% of ameloblastomas are found within the mandible, with the molar-ascending ramus area being the most common site. The average age at diagnosis is the middle to late 30s, although a wide age range is common, and a second peak is seen in the seventh decade of life. Odontogenic myxoma demonstrates a strong mandibular predilection, with the premolaremolar area most commonly affected, although the lesion in the present case did not demonstrate the typical “soap bubble” radiographic appearance seen in myxomas. Central odontogenic fibroma should also be considered in the present case. These unusual lesions present in a wide age range, although most patients present between the ages of 11 and 39 years. Central odontogenic fibromas exhibit a slight mandibular predilection, often posterior to the first molar, and most notably demonstrate a strong female predilection. They may cause significant bony expansion and may present as totally radiolucent or with faint internal septa. As the lesion did not appear to be associated with a tooth, nonodontogenic neoplasms and tumors had to be considered in the differential diagnosis in the present case. Vascular lesions such as hemangiomawere unlikely, based on negative aspiration. A central giant cell lesion (central giant cell granuloma) had to be considered, as these non-neoplastic lesions are commonly seen before the age of 30 and with a distinct female predilection. The mandible is affected the majority of the time, although the lesions are typically found anterior to the canines and without a corticated border. Central giant cell lesions have a tendency to cause expansion and may result in tooth resorption. Finally, simple bone cyst (idiopathic bone cavity) had to be considered, as these lesions are typically seen between the ages of 10 and 20 years and are rarely seen in patients above the age of 30. Simple bone cysts are almost exclusively seen in the mandible and may present with slight expansion. Negative aspiration is commonly seen, and surgical exploration is required for diagnosis. Diagnosis and Management: Approximately 2 weeks following the attempted, but unsuccessful, incision and drainage procedure, an excisional biopsy of the lesion was performed. Aspiration of the lucent area was attempted before surgical entry but proved to be negative. At surgery, the lucent defect was found to contain a solid tissue mass without any evidence of a cystic component. Curettage yielded enough tissue to fill three cassettes. Histologic examination of the biopsy material revealed a large majority of the tissue specimen to be composed of a relatively dense background stroma of fibrous connective tissue, within which there was an increased quantity of what appeared to be mildly proliferative odontogenic epithelium (Figure 2A). The odontogenic epithelium grew in thin but elongated strands, cords, and small islands, and the epithelium was fairly uniformly spread through the background fibrous tissue (Figure 2B). In some areas, the background fibrous tissue appeared mildly hypocellular and hyalinized. However, other fragments of tissue in the specimen showed a distinctly different histopathologic appearance. These tissue fragments showed a highly cellular proliferation of fibrohistiocyticappearing cells surrounding an area of central hemorrhage (Figure 2C). Foreign bodyetype giant cells were scattered through the background fibrohistiocytic stroma in a roughly circular distribution around the areas of hemorrhage (Figure 2D). In most areas, the odontogenic fibroma component of the lesion remained separate from, but abutted against, the giant cell component (Figure 3A). Focally, however, the two patterns were intermingled, and giant cells were occasionally found directly adjacent to the odontogenic epithelium (Figure 3B). The diagnosis was hybrid central odontogenic fibroma/central giant cell lesion. Discussion: The occurrence of central odontogenic fibroma containing areas of central giant cell granulomaelike