Characterization of the cellular component of polymorphous low-grade adenocarcinoma by immunohistochemistry and electron microscopy

In order to characterize the cellular component of the polymorphous low-gra de adenocarcinoma (PLGA) of the salivary gland, a morphological and immunoh istochemical study was carried out. Thirty cases of PLGA were studied by li ght microscopy and immunohistochemistry and five cases by transmission elec tron microscopy (TEM). The expression of cytokeratins (CKs) 7,8,10,13,14,18 ,19, vimentin and muscle-specific actin (MSA) was investigated through the streptavidin-biotin method. The majority of tumor cells stained for vimenti n, CKs 8,18 and 7. CK 14 was positive in most cells of the papillary and tr abecular sub-types. Although the expression of CKs 8,18 and 14 varied among the tumors sub-types, a straight relationship between each histologic patt ern and the CK expression could not be delineated. MSA was reactive in only three tumors while CKs 10 and 13 were not detected in any tumor studied. T he absence of MSA and the expression of CKs 8,18 and 7, in most of the tumo r cells, lead to the hypothesis that myoepithelial cells are not the major cellular component of the PLGA. TEM revealed cells exhibiting microvilli an d variable amounts of secretory granules, some of them suggesting an excret ory activity. The presence of CKs 8, 18 and 7, added to the secretory granu les, indicates that PLGA originates from cells located at the acinar-interc alated duct junction. (C) 1999 Elsevier Science Ltd. All rights reserved.