Abstract: BACKGROUND ＆ AIM: To determine the differentiation of myoepithelial cell (MEC) in the development of salivary glands and its pleomorphic adenomas; and the relation between the differentiation and the biological behavior of these adenomas. MATERIAL AND METHODS: 24 embryonic salivary gland samples in different stages and 31 salivary gland pleomorphic adenomas samples were collected. The development of embryonic salivary gland and pleomorphic adenomas were examined by H＆E and CK14, CK19, α-SMA and P63 markers by immunohistochemistry. The relation between myoepithelial cell differentiation and the biological behavior of the pleomorphic adenomaswas was also studied. RESULTS: Luminal cell of secretory and excretory duct appeared to have been derived from luminal cell lineage because they mostly expressed CK19, and less extensively CK14, but never α-SMA. Basal layer of intercalated duct and acinar cell appeared to have been derived from MEC lineage because expressed CK14, α-SMA, and P63. In pleomorphic adenomas, the markers of MEC were positive in spindle cells, some of the epithelioid cells and also the mucoid or chondroid components.Therefore, they were likely to be derived from MEC lineage. The marker of MEC was negative in plasmacytoid cells, clear cells, and the tubular structure of pleomorphic adenomas. Therefore, they were likely to be derived from luminal cell lineage. CONCLUSION： Acinar cell and intercalated duct appeared to have been derived from MEC lineage, and the structure of duct appeared to have been derived from luminal cell lineage.MEC neoplasms have low-grade invasiveness.

Key words: myoepithelial cell, pleomorphic adenomas, development, differentiation