Fetal Myoepithelial Cells of Submandibular Glands and Modified Myoepithelial Cells in Pleomorphic Adenoma Immunohistochemistry and Ultrastructure

= Abstract = To elucidate the divergent expression of tissue markers for myoepithelial cells (MECs) of submandibular glands. fetal submandibular glands (n 1(0). adult submandibular glands (n 10) and pleomorphic adenoma (n 20) are examined for cytokeratin 14(CK-14), vimentin, and a-smooth muscle actin(-SMA) by double immunohistochemical methods. In addition fetal submandibular glands (n 20) and pleomorphic adenoma ( n 3) are studied ultrastructurally to correlate with the immunohistochemical findings. The polyhedral MECs found in the early intermediate developmental stage (EIDS, 19-24 \U!eks) of fetal submandibular gland showed strong CK-14 positivity, \U!ak a-SMA positivity. and occasional vimentin positivity. These polyhedral MECs matured into \U!dge shaped, spindle or dendritic MECs. A large number of dendritic MECs seen in the late developmental stage (LOS, 33·40 weeks) showed a mild CK-14 positivity, strong a -SMApositivity, and negative vimentin. The CK-14 was also expressed strongly for some basal cells of the excretory ducts and rarely of striated ducts. while these ductal basal cells were negative for a -SMA and vimentin. Electron microscopic examination of fetal submandibular glands disclosed abundant intermediate filaments in the polyhedral MECs during the Ems, The intermediate filaments gradually decreased in amount as MECs matured into dendritic MECs in the LOS, and the dendritic MECs became filled with myofibrils. In pleomorphic adenomas the plasmacytoid or modified MECs usually seen in periductal portions showed coexpression of CK-14 a -SMAand vimentin a -SMAin double imrnunostaining.