[2101] Odontogenic Myxoma: Review of Histopathologic, Immunocytochemical and Ultrastructural Features

John Hicks, Rudolfo Laucirica, Chris Finch, Jerry Bouquot. Baylor College of Medicine, Houston, TX; University of Texas Houston School of Dentistry, Houston, TX

Background: Odontogenic myxomas arise from odontogenic ectomesenchyme and involve the mandible and maxilla. Most are located in the mandible (two-thirds). There is a wide age range, with an average age of 25 to 30 years. The typical tumor is asymptomtic with painless jaw expansion, and found incidentally during dental examination. Diagnostic imaging may reveal a unilocular, multilocular or soap bubble lesion, displacing and/or resorbing teeth. The tumor is not encapsulated, infiltrates bone and may require aggressive curettage.
Design: Study population consisted of 4 males and 3 females (age range 3-62 years) with 4 mandibular and 3 maxillary tumors. The tumors ranged in size from 1.5 cm to massive involvement of the entire maxilla with extension to orbital floors. Tissue was available for routine, immunocytochemical (vimentin, MSA, SMA, S100 protein) and electron microscopic examination.
Results: Gross examination demonstrated white to tan, gelatinous to mildly firm tumors with a mucinous character. The tumors were composed of stellate to ovoid to slightly spindled cells within abundant myxoid matrix with infrequent collagen fibers. One tumor showed malignant transformation from typical odontogenic myxoma to an odontogenic myxosarcoma (low grade myxofibrosarcoma). Tumor cells expressed vimentin diffusely, focal SMA and focal MSA, and lacked S100 expression. Electron microscopy showed widely spaced cells with a mesenchymal character and scant cytoplasm. The tumor cells had adherent basal lamina material. The stroma was composed of ground substance with scant scattered to occasional collagen fibers. The odontogenic myxosarcoma had markedly increased cellularity, more elongated spindle cells in close proximity, decreased ground substance and increased collagen fibers.
Conclusions: Odontogenic myxomas may be confused with other myxoid jaw neoplasms, such as myxoid nerve sheath tumor, chondromyxoid fibroma, myxoid fibrosarcoma and other myxosarcomas, especially when small biopsies are taken. Electron microscopy may be helpful in eliminating other malignant processes from the differential diagnosis. Review of diagnostic imaging of a jaw mass and clinical history are important in providing an accurate diagnosis and guiding appropriate surgical management.
Category: Ultrastructural

Wednesday, March 6, 2013 9:30 AM

Poster Session V # 301, Wednesday Morning


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