The tumour is usually well-circumscribed, but not encapsulated. Occasionally, muscle fibres and nerve branches may be entrapped within the tumour. It is composed of round, cup-shaped, fusiform, or polygonal cells with uniform small nuclei and moderate amounts of faintly basophilic cytoplasm; some tumours may show nuclear pleomorphism, hyperchro-

Fig. 4.39 Ectomesenchymal chondromyxoid tumour of the anterior tongue presenting as a small nodule.

matism, and multinucleation, while mitotic figures are scarce {2410}. In addition, the presence of myxoglobulosis-like changes has been reported {1169}. Alcian blue stains at pH 0.4 and 2.5 are positive, while mucicarmine is usually faintly positive in the extracellular matrix. The tumour cells do not stain with the periodic acid-Shiff (PAS). In the histological differential diagnosis other myxoid and chondroid lesions should be excluded, such as focal oral mucinosis, the mucous retention phenomenon, soft-tissue myxoma, nerve sheath myxoma, myxomatous changes in fibrous lesions, chondrosarcoma, chondroid choristoma, and variants of pleomorphic adenoma or myoepithelioma arising from minor salivary glands.


Reactivity with polyclonal and monoclonal anti glial fibrillary acidic protein (GFAP) is positive in almost all reported cases; reactivity with anti-cytokeratin monoclonal antibody has been positive in the majority of cases as well, while variable staining results were observed for S-100, CD57 and smooth muscle actin {2410}.

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