S100, ALPHA-SMOOTH MUSCLE ACTIN AND CYTOKERATIN-19 IMMUNOHISTOCHEMISTRY IN ODONTOGENIC AND SOFT-TISSUE MYXOMAS

Aims-To compare the expression of S100 protein, alpha-smooth muscle ac tin (alpha-SMA) and keratin 19 in odontogenic myxomas and non-odontoge nic myxoid lesions. Methods-Formalin fixed, paraffin wax embedded tiss ue from seven odontogenic myxomas, three soft tissue myxomas, six hype rplastic myxoid dental follicles, two intramuscular myxomas, 12 cardia c myxomas, and seven normal dental follicles were examined immunocytoc hemically for S100 protein, alpha-SMA and cytokeratin 19 using the Str eptavidin-biotin method. Results-A minority of odontogenic myxomas (th ree of seven) were positive for S100 and the staining was of moderate intensity and in all myxofibroblasts. Soft tissue myxomas, normal dent al follicles, intramuscular myxomas, and most enlarged myxoid follicle s were negative. In the cardiac myxomas the cells forming cords and is lands were positive in approximately half (seven of 12), but the dispe rsed stellate myxoblasts were positive in only two cases. A population of cells in all the odontogenic myxomas and hyperplastic dental folli cles contained alpha-SMA, but such cells were sparse in cardiac myxoma s and present in only four cases. Cytokeratin 19 was present in odonto genic epithelium of odontogenic myxoma and follicles. Conclusions-A mi nority of odontogenic myxomas, but not other oral myxoid lesions, may express S100 protein and this could cause difficulty distinguishing my xoma from myxoid nerve sheath tumours. Sparse myofibroblastic cells oc curred in all types of myxoma tested. The epithelium sometimes found w ithin jaw myxomas expresses cytokeratin 19 and this is consistent with an odontogenic origin.