Expansive osseous dysplasia: report of 9 lesions in an African population sample and a review of the literature.

Objectives: The aim of this study was to report on the clinicopathologic features of osseous dysplasias (ODs) that manifest with gross expansion in a black South African hospital population sample.

Study Design: The files of 9 histology-verified expansive ODs in 8 patients were reviewed. The clinical records and radiographs were analyzed and compared with reports in the literature.

Results: The main complaint of all patients was related to expansion of the jaw. All except 1 were female, with ages between 26 and 71 years and sizes of the lesions ranging from 4 to 15 cm. No history of similar lesions in family members was obtained. All lesions occurred in the mandible and 6 crossed the midline. The expansive growth pattern was associated with persistence of radiolucent areas in the lesions which microscopically consisted of cellular fibro-osseous tissue. Resorption of mineralized deposits by osteoclasts was prominent in the radiolucent parts of the lesion. Maturation with enlargement of the radiodense component was associated with a decrease in osteoclast activity and the formation of lobular bone masses and confluent psammomatous mineralized deposits.

Conclusion: We propose the term "expansive osseous dysplasia" for the rare albeit important clinical subcategory of ODs that manifest with progressive jaw expansion. Suspension of osteoclast activity plays an important role in the maturation of the lesions into dense mineralized masses.