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Ectomesenchymal chondromyxoid tumor is a very rare neoplasm that usually develops in the tongue and can be cured by simple surgery.

Classification
Abbreviations: Ectomesenchymal chondromyxoid tumor (ECT)

Definition: Ectomesenchymal chondromyxoid tumor is a very rare, benign intraoral tumor with presumed origin from undifferentiated (ecto)mesenchymal cells. It is thought to be derived from neural crest cells that migrate to this location. There are a few authors who think this is a soft tissue myoepithelioma, but there are some differences.

Epidemiology
This is a very rare tumor that occurs over a wide range from 9-78 years old (mean, 37 years), affecting both sexes equally.

Site: Usually develops within the anterior dorsal tongue, although rare cases have been reported in other sites (hard palate, base of tongue).

Presentation: Patients usually experience a slowly growing mass in the mouth, that is painless, lacking any surface ulceration or erosion.

Treatment: Surgery is the treatment of choice, that yields a very good outcome with only isolated cases reported to recur when they have been inadequately removed.

Pathology findings
The gross appearance is that of a well circumscribed but not encapsulated submucosal nodule, often with a tan-yellow, to gelatinous appearance when cut. The tumors range from 0.3 up to 2 cm.

Histologic Features There is a well defined nodule(s) separated by fibrous connective tissue. The population that makes up the tumor is comprised of uniform-appearing small hyperchromatic nuclei with basophilic to eosinophilic to clear-appearing cytoplasm. The cells may be arranged in cords, strands or net-like sheets of cells. There is usually not nuclear pleomorphism, multinucleated or increased mitoses. There is a background of chondromyxoid material, but hyalinized stroma make also be seen. Sometimes, there is swirling to suggest neural structures. However, glandular &/or myoepithelial components are absent. The tumor may entrap normal skeletal muscle fibers and nerve branches/twigs.

Histochemistry
• Alcian blue will be positive in the stromal matrix. • Periodic acid-Schiff is negative. • Mucicarmine will be positive in the stromal matrix, but not within the cytoplasm of the cells.

Immunohistochemistry
• Glial fibrillary acidic protein (GFAP) positive in 100% • Cytokeratin positive > 90% • S100 protein positive > 60% • Smooth muscle actin positive > 50% • Negative immunohistochemistry markers include epithelial membrane antigen, desmin, p63 and calponin.

Differential diagnoses
Several different tumors should be considered in the differential diagnosis and then excluded. These include soft tissue myoepithelioma, pleomorphic adenoma, myxoid neurofibroma, nerve sheath myxoma, ossifying fibromyxoid tumor of soft parts, extraskeletal myxoid chondrosarcoma, and chondroid choristoma.