RPC of the Month from the AFIP

Abstract

A symptomless swelling of an 8-year-old boy's right mandible was considered to be a dentoalveolar abscess but was unsuccessfully treated with antibiotics. From the intrinsic morphologic data in Figure 1, list the most probable radiographic diagnoses and indicate which one should be primarily considered prior to biopsy and histologic diagnosis. Radiographic Findings and Discussion Frontal and lateral projections of the mandible (Fig. 1) reveal a poorly marginated area of destruction extending from the alveolar ridge to the inferior border of the mandible. This ill-defined, “moth-eaten” destructive process engulfs the periapical portion of the second bicuspid and part of the first molar. There is no reparative sclerosis or other evidence of mineralization around the lesion, but the medullary cavity is slightly expanded laterally and inferiorly where periosteal new bone formation of a thick homogeneous (“swedged”) variety is present. Except for those lesions engendered by the peculiarity of odontogenesis, the mandible is subject to the same diseases or injuries as other membranous bones and also reacts to stimuli with the same limited variety of host responses. Therefore, while we must include odontogenic cysts and tumors, we must still develop our differential diagnostic list on the basis of the morphologic changes seen in the radiograph, and specific entities will be chosen from the broad categories of trauma, inflammation, anomalies, neoplasms, metabolic disease, circulatory disturbances, and mechanical adaptations. Usually an osteolytic pattern such as that seen in Figure 1 prompts consideration of a rapidly destructive lesion, as osteolytic sarcoma, metastatic disease, or the so-called “round-cell” lesions of bone. The latter include metastatic neuroblastoma, Ewing's sarcoma, reticulum-cell sarcoma, myeloma, histiocytosis X, and lymphoma. These are grouped together because of their often similar pathologic constituent, a nondescript undifferentiated sarcoma-like round cell. Radiographically, they all may cause a similar pattern of disturbed architecture, with or without periosteal reaction. Since this characteristic morphologic change is in the mandible, however, lesions peculiar to the jaws now must enter into the differential and will include odontogenic cysts, either follicular or inflammatory, and extension of inflammatory conditions related to periapical infections or advanced periodontal disease. At first glance you may wish to include ameloblastoma in your list but its usual appearance is multilocular or unilocular, and only on rare occasions does it present with a moth-eaten, ill-defined osteolytic pattern. Moreover, the “swedged” or solid periosteal new bone is inconsistent with this diagnosis. Most commonly, the tooth-associated lesions tend to become circumscribed and walled off from the surrounding tissues.