Tumors of Odontogenic Ectomesenchyme principally of ectomesenchymal elements. Although odontogenic epithelium may be included within these lesions, it does not appear to play any essential role in their pathogenesis.

ODONTOGENIC MYXOMA from odontogenic ectomesenchyme. a close microscopic resemblance to the mesenchymal portion of a developing tooth. mesenchymal portions Of a developing tooth DF all myxomas of the jaws are currently considered to be of odontogenic origin.

predominantly found in young adults but may occur over a wide age group. (25 to 30 years) no sex predilection Smaller lesions may be asymptomatic Larger lesions are often associated with a painless expansion of the involved bone. In some instances clinical growth of the tumor may be rapid this is probably related to the accumulation of myxoid ground substance in the tumor

Radiographically a unilocular or multilocular radiolucency that may displace or cause resorption of teeth in the area of the tumor. The margins of the radiolucency are often irregular or scalloped. The radiolucent defect may contain thin, wispy trabeculae of residual bone, which are often arranged at right angles to one another Stepladder pattern

Large myxomas of the mandible may show a "soap bubble" radiolucent pattern

Histopathologic Features gross examination the gelatinous, loose structure Haphazardly arranged stellate, spindle-shaped, and round cells in an abundant, loose myxoid stroma that contains only a few collagen fibrils ground substance:glycosaminoglycans, chiefly hyaluronic acid and chondroitin sulfate.

A loose, myxomatous tumor can be seen filling the marrow spaces between the bony trabeculae. stellate-shaped cells and fine collagen fibrils.

The lesion is highly myxoid, hypocellular, and devoid of atypia

Small islands of inactive-appearing odontogenic epithelial rests may be scattered throughout the myxoid ground substance. These epithelial rests are not required for the diagnosis and are not obvious in most cases. In some patients, the tumor may have a greater tendency to form collagen fibers; such lesions are sometimes designated as fibromyxomas or myxofibromas. Myxoid change in an enlarged dental follicle or the dental papilla of a developing tooth may be microscopically similar to a myxoma. Evaluation of the clinical and radiographic features prevent overdiagnosis of these lesions as myxomas.

Treatment and Prognosis Small myxomas are generally treated by curettage. periodic reevaluation is necessary for at least 5 years. For larger lesions, more extensive resection (myxomas are not encapsulated and tend to infiltrate the surrounding bone) Recurrence rates:25% In spite of local recurrences, the overall prognosis is good, and metastases do not occur.