Pleomorphic adenomas, adenoid cystic carcinomas and adenolymphomas of salivary glands analysed by a monoclonal antibody against myoepithelial/basal cells. An immunohistochemical study

Immunocytochemical identification of different cell types in bovine nasolabial glands with particular emphasis on cytoskeletal protein expression

Nasolabial glands are serous glands forming a thick subcutaneous layer in the bovine muzzle. In order to identify the different epithelial cell types, both immunofluorescent and immunoperoxidase techniques were employed on frozen and fixed sections using monoclonal antibodies to cytoskeletal proteins and S-100. Actin was also detected with phalloidin. The results show that four cell types can be identified on the ground of the different composition of the cytoskeletal filaments: acinar, basket, luminal duct and basal duct cells. Acinar, luminal duct cells and basal duct cells express different patterns of cytokeratins, as shown by the 12 anti-cytokeratin monoclonal antibodies used, and both basket cells and the basal cells of intercalated ducts are also reactive to phalloidin and anti-alpha-smooth muscle actin monoclonal antibody. The presence of actin supports the conclusion that basal duct cells are also contractile elements, i.e. myoepithelial cells. Vimentin, glial fibrillary acidic protein (GFAP), and S-100, molecules considered to be markers of myoepithelial cells by many AA., were not found. The intermediate filaments of the duct epithelium appear more complex and heterogeneous in comparison with those present in the acinar cells.

Basket and basal-duct cells in domestic animals: different cytokeratin expression and shape

Cytokeratins (CKs) are a multigenic family of proteins constituting intermediate filaments in epithelia, indicated in humans by the numbers 1-20. Different cell-types can be immunocytochemically identified on the grounds of their CK expression. This investigation was designed to study CK expression of basket cells (BCs) and basal-duct cells (BDCs) in some domestic animals. Frozen sections of mammary and major salivary glands from cows, sheep, pigs and rabbits were treated using the immunofluorescent method, using as monoclonal antibodies clones CK-E3, CKB1, KS-1A3, and LDS-68, respectively, revealing the human CKs 17, 14, 13, 7. BCs surrounding acini and BDCs were stained by CK 17 antibody only in the rabbit. CK 14 was detectable in both cell types in cows, sheep and pigs, except in the case of bovine salivary BCs. CK 13 was revealed in BCs and BDCs of all mammary glands and also rabbit salivary glands. In the salivary glands of the other species, only BDCs were stained. CK 7 gave unreliable results in all the species and cell types examined. Interestingly, in the rabbit, also BDCs are basket-like in shape. The antibodies employed showed different staining depending on species and gland. On the grounds of immunoreactivity and shape, BCs and BDCs can be considered the same cell type in the rabbit. In the other species, they appear to be different, since BDCs may express additional CKs and are triangular-shaped, whereas BCs are truly basket-like. It is worth noting that clone KS-1A3 in the rabbit and CKB1 in the sheep and pig can be considered markers of the basket/ basal system.

Expression of cytokeratins in Warthin's tumour (adenolymphoma) of parotid glands: specific detection of individual cytokeratin types by monoclonal antibodies

This study evaluated the distribution of cytokeratins detected by monoclonal antibodies directed against individual keratin proteins in normal human salivary glands and epithelial tumour cells of Warthin's tumour arising in parotid glands to determine a more precise mapping of their cellular distribution. The normal salivary ducts showed the presence of cytokeratin 7, 8, 18 and 19 in the intercalated, striated and excretory ducts, the primary keratins of stratified and simple epithelia with a profile very similar to the non-cornified epithelium of the oral mucosa. The basally located cells of salivary gland ducts other than myoepithelial cells were reactive for keratins 7 and 19 suggesting a close similarity in profile of keratin in the basal cells of the oral epithelium. In Warthin's tumour, keratins 7, 8, 18 and 19 were consistently detected in the epithelial cells of the tumour, a profile with a tendency to mimic the same in normal ductal epithelium. The distribution, however, was diverse and a heterogeneity was observed in the basal and luminal cells of Warthin's tumour which differed even in different areas of the same tumour specimen.

Thomsen-Friedenreich (T) antigen as marker of myoepithelial and basal cells in the parotid gland, pleomorphic adenomas and adenoid cystic carcinomas. An immunohistological comparison between T and sialosyl-T antigens, alpha-smooth muscle actin and cytokeratin 14

Controversy centres on the role and identification of myoepithelial (MEC) and basal cells in salivary gland tumours, and recent studies suggest that both basal cells and myoepithelial cells participate in the formation of salivary gland tumours. We have correlated the expression of different well-known markers of normal MEC/basal cells (i.e. alpha-smooth muscle actin and cytokeratin 14) with T (Thomsen-Friedenreich) antigen and its sialylated derivative: sialosyl-T antigen,) in 17 normal parotid glands and in two tumour types with MEC participation (i.e pleomorphic adenomas (PA) and adenoid cystic carcinomas (ACC)) using immunohistology with well-defined monoclonal antibodies (MAbs). Paraffin-embedded/fresh frozen tissue sections were studied from 33/17 patients with PA and 15/7 patients with ACC. In normal parotid tissue coexpression of alpha-smooth muscle actin, cytokeratin 14, T and sialosyl-T antigens was found in all MEC and in some of the basal cells lining striated ducts. The remaining basal cells exclusively expressed cytokeratin 14, T and sialosyl-T antigens. In the tumours, cells believed to be modified myoepithelial cells showed two different staining patterns: 1) Coexpression of alpha-smooth muscle actin, cytokeratin 14, T and sialosyl-T antigens, and 2) Coexpression of cytokeratin 14, T and sialosyl-T antigens, but no alpha-smooth muscle actin. The epithelial ductular structures in the tumours showed aberrant expression of cytokeratin 14, T and sialosyl-T antigens, and cytokeratin 14 was the only marker of cells in solid undifferentiated areas of adenoid cystic carcinomas. Our study supports the view, that modified "myoepithelial" cells in the tumours consist of a mixture of basal cells and myoepithelial cells. None of the investigated structures was in itself an ideal marker in the identification of MEC/basal cells. The cells can be identified by a combination of markers (i.e. cytokeratin 14, alpha-smooth-muscle actin, T and sialosyl-T antigens).

Diagnostic criteria for neoplastic myoepithelial cells in pleomorphic adenomas and myoepitheliomas. Immunocytochemical detection of muscle-specific actin, cytokeratin 14, vimentin, and glial fibrillary acidic protein

OBJECTIVE

Markers for normal salivary gland myoepithelium were used to determine the extent of their expression in the neoplastic myoepithelial (nonluminal) cells of pleomorphic adenomas and then in the tumor cells in myoepitheliomas and to gather information necessary to establish diagnostic criteria, especially muscle actin expression, for myoepitheliomas.

STUDY DESIGN

Methanol/acetic acid-fixed and paraffin-embedded tissue was used to immunohistochemically study expression of intermediate and smooth-muscle actin filaments in nonluminal cells in 14 pleomorphic adenomas and to compare this to their expression in five myoepitheliomas.

RESULTS

In routine histologic sections, the morphologic variants of nonluminal tumor cells--spindle, stellate, polygonal, angular, and plasmacytoid--in pleomorphic adenoma mirror the spectrum of tumor cells in myoepitheliomas. Immunocytochemical similarities are also apparent. Two specific markers for myoepithelial cells in the normal salivary gland, muscle-specific actin and cytokeratin 14, were both variably, independently, and never uniformly expressed in nonluminal cells of pleomorphic adenoma and tumor cells in myoepitheliomas regardless of their morphology. Cytokeratin 14 in addition labels basal cells of excretory ducts. Both muscle-specific actin and cytokeratin 14 preferentially localized to single layers of periductal cells in pleomorphic adenomas, angular, polygonal, and plasmacytoid cells preferentially expressed cytokeratin 14. Similar patterns were noted in the three myoepitheliomas with reasonable expression of the two markers. Only isolated single cells or small groups of plasmacytoid cells in four pleomorphic adenomas with a significant component of these cells and the two plasmacytoid myoepitheliomas immunostained for muscle-specific actin and cytokeratin 14. In both tumor types, vimentin was nearly uniformly expressed in nonluminal tumor cells of all morphologic types, including plasmacytoid cells.

CONCLUSIONS

The range and transition of morphology of nonluminal cells in pleomorphic adenomas is reflected in myoepitheliomas. Incomplete or absent expression of the myoepithelial/basal cell markers, muscle-specific actin, and cytokeratin 14, and the general expression of vimentin is common to both tumors. Because these findings apply to the majority of plasmacytoid cells in pleomorphic adenomas, tumor cells with a similar morphology and immunoprofile are to be expected in myoepitheliomas; the term plasmacytoid myoepitheliomas is thus appropriate regardless of the presence or absence of muscle-specific actin.

Myoepithelium of salivary glands

In salivary glands and other exocrine organs, there are starfish-shaped cells that lie between the basal lamina and the acinar and ductal cells. These have structural features of both epithelium and smooth muscle cells, and so are called myoepithelial cells. Their functions include contraction when the gland is stimulated to secrete, compressing or reinforcing the underlying parenchymal cells, thus aiding in the expulsion of saliva and preventing damage to the other cells. They also may aid in the propagation of secretory and other stimuli. Their common developmental origin with the basal cells of the larger ducts is displayed in the mature glands by shared structural and immunohistochemical features, but most such basal cells do not have the distinguishing features of myoepithelial cells, such as myofibrils. Although myoepithelial cells can be identified by light microscopy through enzyme histochemistry and special stains and immunohistochemistry for their myofibrils, these techniques can be misleading in salivary gland neoplasms. Thus, the most reliable means of identifying neoplastic myoepithelial cells is with a combination of histochemistry and electron microscopy. The extent to which these cells are derived from undifferentiated stem cells in both normal and neoplastic growth is controversial. The presentation here of transmission electron microscopy (TEM) of well-differentiated myoepithelial cells in mitotic division indicates that stem cells are not necessarily the only source of myoepithelial cells in the later stages of salivary gland development or in neoplasia.

Prenatal development of myoepithelial cell of human submandibular gland observed by immunohistochemistry of smooth muscle actin and rhodamine-phalloidin fluorescence

Immunostaining of monoclonal antibody (MoAb) of smooth muscle actin in paraffin sections and fluorescence of actin-specific phalloidin in cryostat sections were utilized to demonstrate the myoepithelial cells in prenatal and adult salivary glands of humans. In the early developmental stage (10-18 weeks) MoAb actin was weakly positive in the basal cells of the gland epithelium, and the positivity gradually accentuated at the basal portions of the terminal ducts and acini as the gestational period advanced. In the early intermediate developmental stage (19-24 weeks) the polyhedral myoepithelial cells were arranged in the basal portions of the acini and intercalated ducts. At this stage the myoepithelial cells produced phalloidin-positive spindle cytoplasmic processes. In the late intermediate developmental stage (25-32 weeks) the myoepithelial cells became flattened and formed dendritic processes to surround the acini and intercalated ducts. In the late developmental stage (33-40 weeks) numerous myoepithelial cells with well developed dendritic processes were demonstrable in the acini and intercalated ducts. In conclusion, it was found that the myoepithelial cells began to develop at 15-16 weeks of gestation when the acinar cells were still immature. The primitive myoepithelial cells were polyhedral in shape to form compact basal layer beneath the developing acinar cells during 19-24 weeks of gestation. In late gestational period the myoepithelial cells almost matured like the dendritic ones of adult salivary glands. However, the myoepithelial cells were never demonstrated in the striated and excretory ducts of the fetal salivary glands as opposed to its normal presence in the adult salivary glands. A possible aging process of myoepithelial cells was discussed in accordance with the histogenesis of transformed myoepithelial cells of salivary gland tumors.

Cytokeratin expression in normal and (pre)malignant head and neck epithelia: an overview

Intermediate filament proteins (IFPs) are important markers of tissue differentiation and have been receiving increasing interest, in particular, through their applicability in the characterization of malignant tumors. Cytokeratins (Cks) are a family of IFPs that are typically specific for epithelial cells. They are expressed in certain combinations depending on the type of epithelium and the degree of differentiation. This review presents a critical analysis of the available data on Ck expression in normal and (pre) neoplastic epithelia of the head and neck region. Special attention is paid to technical and cell biologic pitfalls, which can lead to false-negative or false-positive data. It appears that only a limited fraction of the reported data contributes substantially to our knowledge of IFP expression in head and neck cancer because of the use of ill-defined, often formalin-fixed and paraffin-embedded, tissue specimens, and the application of limited panels of monoclonal antibodies. It is concluded that the use of immunocytohistochemistry is promising for the differential diagnosis of head and neck tumors and contributes to our knowledge on their biologic behavior. However, documentations of more complete Ck expression patterns of normal and (pre)malignant epithelium are required, together with their correlation to clinical parameters.

Comparative cytofluorometric DNA analysis of pleomorphic adenoma and adenoid cystic carcinoma of the salivary glands

The nuclear DNA content in the tumor cells of 17 pleomorphic adenomas (PA) and 26 adenoid cystic carcinomas (ACC) was assayed by cytofluorometry to clarify the etiology of the differences in their biological nature. Aneuploidy was found in only two solid-pattern ACC samples; all the other samples had diploid stemlines. With respect to the polyploid cell rate and the S + G2M fraction, the differences between the four histological patterns of PA were not significant. In the ACC, the S + G2M fraction was significantly higher in solid pattern than in cribriform or trabecular pattern tumors, which may indicate that proliferative activity is higher in the solid pattern than in the other two. The polyploid cell rate in ACC was significantly higher in the solid pattern than in the cribriform pattern carcinomas. There was no significant difference in the mean polyploid cell rate between PAs and ACCs. The mean S + G2M fraction was significantly higher in all histological patterns of ACCs than in PAs. These results suggest that proliferative activity is greater in any one of the histological patterns of ACC than in PA. These findings may largely explain the biological differences between the two tumors.

Altered expression of ABO (H) carbohydrate antigens is seen in pleomorphic adenomas

Cell surface carbohydrate antigens show changes in relation to differentiation, maturation and malignant transformation. The expression of type 2 chain ABH carbohydrate structures of the ABO histo-blood group system was investigated in 28 pleomorphic adenomas (PA) and normal parotid glands in order to study possible changes in the glycosylation pattern. The distribution of carbohydrate structures was investigated by immunohistological stainings of formalin-fixed paraffin-embedded material using monoclonal antibodies (MAbs) with well-defined specificity. A strong interindividual variation was found in the normal tissue as well as in the tumors. In normal tissue, acinus and duct cells all expressed elongated carbohydrate structures. The yoepithelial cells did not stain with any of the MAbs investigated. In the PAs, staining was seen in the ductular structures and myoepithelial cells. In contrast to normal tissue, the tumors expressed the short precursor molecule sialylated N-acetyllactosamine. Furthermore, the PAs showed loss of H and A antigens, and a reduced expression of Le(y) compared to normal tissue. The ductular structures as well as the modified myoepithelial cells expressed binary N-acetyllactosamine, which in the normal tissue could only be found in the striated and excretory ducts. Thus our study has shown that aberrant glycosylation is not only a feature of malignant neoplasms but also occurs in pleomorphic adenomas.

Cytokeratins, smooth muscle actin and vimentin in human normal salivary gland and pleomorphic adenomas. Immunohistochemical studies with particular reference to myoepithelial and basal cells

The distribution of immunostaining in normal major salivary gland and in 12 pleomorphic adenomas was studied using monospecific monoclonal antibodies to a number of cytokeratins, including cytokeratin 14, to smooth muscle actin and vimentin. A number of these antibodies enabled a distinction to be made between structural components of the normal gland, and to relate this to the different structures of pleomorphic adenomas. In the normal gland, the luminal duct cells expressed cytokeratins 7, 8, 18 and 19. Three antibodies were of particular value for the characterization of normal myoepithelial and basal cells; while the antibody to smooth muscle actin and the cytokeratin antibody Ks8.12 mutually exclusively stained the myoepithelial (basket) cells and the basal duct (light) cells, respectively, the recently established monospecific antibodies to cytokeratin 14 showed specific immunostaining with both cell types. These three antibodies left luminal cells virtually unstained. Ck 13 was found occasionally in single luminal excretory duct cells. Antibodies to cytokeratins 1/2, 10 and 10/11 did not show any staining in the normal gland. In the pleomorphic adenomas, the staining pattern of the two-layered tubular formation resembled that of the normal gland ducts: tumour luminal cells showed the characteristic, although more irregular, expression of cytokeratins 7, 8, 18 and 19; the outer cells resembled normal ductal basal cells with their anti-cytokeratin 14/Ks8.12-epitope staining and in that they virtually lacked staining for smooth muscle actin. Trabecular formations and cells in myxoid areas were reactive with Ks8.12 and for cytokeratin 14, occasionally also for cytokeratins 7, 18 and 19. Epidermoid cell islets expressed mainly cytokeratin 14 and inconsistently the squamous epithelial cytokeratin 13 and the epidermal cytokeratin 10/11. Vimentin was found in cells of myxoid areas. The results support the postulate that some of the normal duct basal cells act as reserve cells and can give rise to tumour formation with a primitive myxoid or trabecular pattern and a more differentiated tubular or epidermoid configuration.

Immunohistochemical localization of MAM-3 and MAM-6 antigens in adenoid cystic carcinoma

MAM-3 and MAM-6 antigens were detected immunohistochemically in 34 cases of adenoid cystic carcinomas (ACC) of the salivary glands and these patterns were compared to these of epithelial membrane antigen (EMA) and laminin. ACC was histologically divided into three types; the cribriform pattern, the tubular and trabecular pattern, and the solid cluster pattern. Immunostaining of EMA and MAM-6 antigen had a similar distributions in the luminal borders of luminal tumor cells, whereas the MAM-3 antigen was slight or negative in luminal borders. Myoepithelial derived tumor cells of ACC accompanying hyaline stroma demonstrated positive staining for the MAM-6 antigen (whole cell positive type), and luminal tumor cells of microcysts showed strong staining for the MAM-3 antigen. Laminin staining was confined to the basement membrane and surface borders in pseudocyst cavities. In salivary gland ACC, laminin staining can be used as a marker of pseudocyst surfaces and immunostaining of EMA and the MAM-6 antigen as a marker of luminal borders of cyst. These two histochemical markers were useful for discriminating pseudocyst and cyst.

Basaloid carcinoma of salivary glands, a variety of undifferentiated adenocarcinoma. Immunohistochemical study of intermediate filament proteins in 24 cases

Among adenoid cystic carcinomas of salivary glands (ACCs), the solid basaloid type has a poor prognosis similar to that of undifferentiated adenocarcinomas. We studied 24 cases in immunohistochemistry using antibodies reactive with keratins of various molecular weights, vimentin, S-100 protein, and its A and B subunits. Our findings were correlated with the histological pattern and with the variable degree of differentiation of these carcinomas. In comparison with other types of ACC, intermediate filament proteins in this group were weakly expressed. The co-expression of cytokeratin and vimentin was noted in some cases. Additional features noted were the presence of cribriform cavities associated with solid lobules and areas of necrosis giving a comedocarcinomatous pattern. In these two variants, cells characterized by the dual expression of cytokeratin and S-100 protein were seen. In the highly malignant anaplastic variety, only a few cells were weakly positive with antisera to cytokeratin and vimentin. This group shows similarities to undifferentiated adenocarcinomas of salivary glands. Such similarities could be explained by the common origin of these tumours from intercalated ducts.

Immunohistochemical studies of S-100 protein alpha and beta subunits in adenoid cystic carcinoma of salivary glands

Immunohistochemical studies were performed to explore the distribution of S-100 protein and its alpha, beta subunits in 76 adenoid cystic carcinomas (ACC) of the salivary glands. Histopathologically. ACC was divided into cribriform, tubular, basaloid and trabecular types which could be mixed in the same tumor. S-100 protein was usually positive in tumor cells forming cribriform structures; foci of strongly positive tumor cells were also distributed in the luminal layer of tubular structures, and in areas transitional between cribriform and tubular patterns. S-100 alpha staining was confined to some tumor cells in cribriform areas, to luminal tumor cells in tubular structures and to few tumor cells in basaloid structures. S-100 beta reaction was usually localized to luminal surfaces in a fine granular pattern in tubular and microtubular structures in a distribution somewhat similar to that in the normal salivary gland. Great heterogeneity in the immunohistochemical distribution of S-100, S-100 alpha and S-100 beta proteins was found in the various histologic types of ACC and the pattern was different from that seen in pleomorphic adenomas. It is possible that the ACC tumor cells positive for S-100 protein may be closely related to true or modified myoepithelial cells.

Immunohistochemical localization of vitamin B12 R-binder in salivary gland tumors. Implications for cell differentiation

Vitamin B12 R-binder, a specific binding protein for vitamin B12, was studied immunohistochemically in normal and 106 neoplastic salivary gland tissues with a monoclonal antibody against vitamin B12 R-binder (R-binder). In normal salivary glands, R-binder localization was restricted to the ductal systems and to mucous acinar cells; serous acinar cells, myoepithelial cells and stromal connective tissues were consistently negative. Among salivary gland tumors, R-binder was present in 87% of pleomorphic adenomas, 100% of monomorphic adenomas, and 40% of adenoid cystic carcinomas; positivity was observed only on luminal surfaces of small ductular elements, indicating that the components closely related to ductal differentiation were rather small in population. R-binder could be detected both in lacunar and non-lacunar cells within chondroid areas of pleomorphic adenomas, suggesting the possibility that chondroid regions arise from metaplastic changes in ductal epithelial cells. In mucoepidermoid tumors, mucous cells and focal squamous cells exhibited cytoplasmic staining. The staining pattern for R-binder in epithelial components of adenolymphomas showed close similarities to those found in normal large excretory ducts. Two acinic cell tumors and one case each of myoepithelioma and malignant myoepithelioma exhibited negative reactivity for R-binder, showing that these neoplasms are solely composed of tumor cells without the characteristics of ductular differentiation. The immunohistochemical examination of salivary gland tumors, employing a monoclonal anti-R-binder antibody, may have some implications for cellular heterogeneity and differentiation in various tumors.

The cellular composition of basal cell adenoma of the parotid gland: an immunohistochemical analysis

Four cases of basal cell adenoma of the parotid gland were examined immunohistochemically to characterize their cellular composition. In all cases epithelial membrane antigen and keratin were detected in the inner luminal cells; some cells also showed positive staining for secretory functional markers, indicating their differentiation toward secretory epithelium. In tubular and trabecular types the outer cells consistently displayed an intense staining for vimentin and some were also positive for actin, indicating their myoepithelial nature. In the solid type, most tumor cells resembled the ductal cells or basal cells of larger ducts in normal gland with regard to their immunoreactivity. Our results may suggest that the proportion and arrangement of heterogeneous tumor cells are responsible for different histologic patterns of the salivary basal cell adenoma.

Immunohistochemical characterization of epithelial cells in human lacrimal glands. I. Normal major and accessory lacrimal glands

Expression patterns of cytokeratins (CKs), actin, lactoferrin (Lf), lysozyme (Ly), vimentin, and S-100 protein were immunohistochemically examined in paraffin sections from eight normal major and accessory lacrimal glands (LGs). Luminal duct cells and a number of secretory cells stained with the antibodies (ABs) KL1 and Pkk1 (CK 7, 8, 17, 18), while basal duct and myoepithelial cells reacted with the AB 34 beta E12 (CK 5). Myoepithelial cells expressing CK 5 and actin were restricted to acini and intralobular ducts, and their number was greater in major LGs than accessory ones. Lf and Ly were found in 50%-75% of acini and intralobular ducts. Vimentin was absent in parenchyma of LGs. S-100 protein reaction was observed in a number of acinar and luminal duct cells of major LGs whereas epithelia of accessory LGs remained negative. Distribution patterns of CKs, Lf, and Ly in major and accessory LGs are identical. The difference with respect to the number of myoepithelial cells as well as S-100 protein reactivity between major and accessory LGs reactivity appeared to be relevant to the differences in their secretory mechanisms and local environment.

Multiple expression of keratins, vimentin, and S-100 protein in pleomorphic salivary adenomas

Immunohistochemical staining for S-100 protein and the intermediate filaments keratin and vimentin, was made in 41 salivary adenomas. In pleomorphic adenomas, great heterogeneity in the staining, as well as multiple and co-expressions of these proteins were found in the outer tumor cells of tubulo-ductal structures and modified myoepithelial cells, but not in the luminal tumor cells. All the outer tumor cells stained for S-100 protein, 97% for K8.12 keratin and 85% for vimentin. Of these cells, 29% showed multiple expression of K8.12 keratin, vimentin, and S-100 protein, and 17% showed co-expression of K8.12 and S-100 protein. Modified and neoplastic myoepithelial cells showed similar expressions of these proteins to those of outer tumor cells; myoepithelioma cells displayed the most complicated pattern, being positive for KL1, PKK1, and K8.12 keratins, vimentin and S-100 protein. In luminal tumor cells there was a heterogeneous expression of KL1 and PKK1 in 82%, and of KL1, PKK1, and K8.12 in only 14.7%. Based on the immunohistochemical findings obtained with different monoclonal antibodies in pleomorphic salivary adenomas, outer tumor cells may be derived from ductal basal cells and luminal tumor cells from intercalated duct cells.

Histogenesis of salivary gland neoplasms: a postulate with prognostic implications

In a continually renewing cell population, stem cells can be regarded as a reservoir of cells with a high capacity for self renewal that give rise to all differentiated progeny. They are the primary source for the generation and maintenance of cellular diversity and tissue homeostasis. In general, neoplasms manifest differentiation pathways similar to those found in the development and renewal of the normal tissues from which they arise. This feature serves as a basis for classification schemes of neoplasms and, as in the normal tissues, there is usually an inverse correlation between proliferative capacity and differentiation within the neoplasms. In our postulate of the histogenesis of salivary gland neoplasia, we evoke the stem cell model to account for the considerable phenotypic heterogeneity seen with these neoplasms. We further consider the neoplasms and, in particular, their myoepithelial constituencies to be manifestations of escape from normal regulatory mechanisms that determine differentiation pathways which a stem cell and its progeny can take. Clinical and basic scientific evidence are presented to support the postulate and also to point to the mitigating role that myoepithelial differentiation has in the biological course of salivary gland neoplasms.

Heterogeneity of keratin expression in epithelial tumor cells of adenolymphoma in paraffin sections

Immunohistochemical expressions of keratin polypeptides detected by monoclonal antibodies were described in tumor cells of adenolymphoma, and the possibility of intercalated duct and ductal basal cells in the salivary glands being the progenitors was discussed. Basal cells in the tumor showed positive staining for keratin nos. 8, 13, 16, 18 and 19 detecting for monoclonal keratin antibodies (PKK 1, K 4.62, K 8.12, K 8.13), columnar tumor cells displayed strongly positive reactions with RPN 1164 and K4.62 suggesting keratin nos. 8 and 19. Great heterogeneity of distribution for keratin polypeptides was displayed by epithelial cells of adenolymphoma. Intercalated duct cells of normal salivary glands reacted with RPN 1164, RPN 1165, K 4.62 and K 8.13 monoclonal antibodies, which indicates the presence of keratins 8 and 19; and ductal basal cells reacted with PKK 1, K 4.62 and K 8.12, suggesting nos. 8, 13, 16, 18 and 19 keratins. Distribution of involucrin was variable in tumor epithelium of adenolymphoma, and was negative in the normal gland. The immunohistochemical distribution of keratin types between basal tumor cells of adenolymphoma and ductal basal cells of the normal salivary gland was compared.

Coexpression of keratin and vimentin in salivary pleomorphic adenomas

The coexpression of keratin and vimentin is described in 45 pleomorphic adenomas using an immunoperoxidase MAb method. Histopathologically, the outer layer of tubuloductal structures and peripheral tumor cells in solid masses, including modified or neoplastic myoepithelial cells, showed positive staining with monoclonal keratin antibody K8.12 and vimentin. This staining was found in the ratio of 10/26 (38.5%) in tubuloductal structures, 2/7 (28.6%) in peripheral tumor cells and 8/12 (66.7%) in modified myoepithelial cells. Concomitant staining of other keratin antibodies (PKK1, KL1) and vimentin did not exist. In addition, the ductal basal cells of normal salivary glands showed positive K8.12 labelling. The histogenesis of pleomorphic adenoma is discussed in relation to the differentiation of either ductal basal cells or ductal luminal cells from a single stem cell origin or the direct transformation of ductal basal cells to outer tumor cells and/or modified myoepithelial cells, both coexpressing K8.12 and vimentin.

Salivary gland myoepithelioma variants. Histological, ultrastructural, and immunocytological features

The histological and ultrastructural features of five major salivary gland tumours, which have little or no evidence of duct- or gland-type differentiation in routine sections, are described. Four of the cases have the tumour cells organized as narrow, anastomosing cords of cells separated by a myxoid and vascularized stroma; we have designated such lesions as reticular-type myoepitheliomas. The fifth case has a solid growth pattern and is largely composed of hyaline cells, that is, a plasmacytoid myoepithelioma. Ultrastructurally, one reticular myoepithelioma reveals myoepithelial cell differentiation with microfilament aggregates, while the other three examples are composed of modified myoepithelial cells displaying widened intercellular spaces, prominent synthesis of extracellular glycosaminoglycans, distinct basal lamina development, and obvious accumulations of cytoplasmic intermediate filaments. In electron micrographs, the modified myoepithelial cells of the plasmacytoid variant closely resemble the tumour cells in the reticular form. Three cases had expression of both glial fibrillary acid protein (GFAP) and vimentin, but only one of the myoepitheliomas contained muscle-specific actin. At least focally, each of the cases exhibited a considerable spectrum of cytokeratin filaments. Using double-labeled immunofluorescent microscopy of one reticular variant and the plasmacytoid myoepithelioma, there was individual tumour cell co-expression of GFAP and vimentin focally in the plasmacytoid myoepithelioma, but co-expression of cytokeratins 13, 16 and GFAP were not noted in either case. As expected, co-expression of high- and low-molecular weight cytokeratin filaments was widespread in both myoepitheliomas. Most described myoepitheliomas have a solid growth pattern and are composed of spindle and plasmacytoid cells, but based on cytological features and growth patterns in this series, it is apparent that polygonal-shaped cells with novel architecture can occur in myoepitheliomas. The results also indicate the close relationship between pleomorphic adenoma and such variants of myoepithelioma.

Diversity of collagen expression in the pleomorphic adenoma of the parotid gland

The high diversity of collagen expression and its qualitative and quantitative aspects are demonstrated in pleomorphic adenoma using electron microscopy and specific histochemical methods. Great variability was observed in the amount, distribution and characteristics of the collagen found in the various types of tissue normally present in this tumour. Both deficient polymerization and hyperpolymerization of collagen and the occurrence of desmoplasia were observed. Evidence is presented to suggest a role for localized collagenolysis in the invasiveness of this neoplasia.

Immunohistochemical expression of MAM-3 and MAM-6 antigens in salivary gland tumours

MAM-3 and MAM-6 antigens of human milk fat globule membrane were detected immunohistochemically in 93 cases of salivary gland tumours as well as in normal glands. The antigens were visualized in 10% formalin-fixed paraffin sections. MAM-3 (MoAbs 115G3, 67D11) antigen was distributed in intercalated and striated duct cells of the normal salivary glands, and in luminal tumour cells and squamous metaplastic cells of pleomorphic adenomas. In pleomorphic adenomas the frequency of positive staining with MoAb 67D11 (54/67; 80.6%) was higher than that with MoAb 115G3 (36/67; 53.7%). MAM-6 (MoAbs 115D8, 115F5) antigen was expressed in luminal and lateral borders of serous acinar cells and ductal of the normal glands, and also in luminal borders of tubulo-ductal and glandular structures of salivary gland tumours. Ductal basal cells were characterized by existence of positive staining for MAM-6 antigen, in adenolymphomas MAM-6 antigen was restricted to the basal tumour cells. Some mucous cells of mucoepidermoid tumours were stained specifically with MoAb 115G3, and epidermoid cells of mucoepidermoid carcinomas manifested MAM-6 antigen staining. Immunohistochemical localization of MAM-6 antigen resembled that of epithelial membrane antigen (EMA) detected with MoAb.

Glial fibrillary acidic protein and desmin in salivary neoplasms. Expression of four different types of intermediate filament proteins within the same cell type

The presence of intermediate filament proteins (IFP) in normal salivary gland tissue and investigated by immunohistochemical techniques on frozen sections. Cytokeratins (CKs) were seen in almost all normal epithelial cells. In the parotid gland and in palatal gland tissue, a co-expression of cytokeratin and glial fibrillary acidic protein (GFAP) was seen in some myoepithelial cells, but this was not apparent in the submandibular gland. In some pleomorphic adenomas, carcinomas in pleomorphic adenomas, one mucoepidermoid carcinoma, one mucus-producing adenopapillary carcinoma and one adenoid cystic carcinoma, cells expressing three different IFP classes were found (CKs, vimentin, GFAP). These cells were most often situated peripherally in the tumour cords or ducts. The cytokeratin pattern in these cells, as revealed by mAbs PKK1-3, was similar to that in normal myoepithelial cells. Furthermore, reactivity for a fourth class of IFP, desmin, could be seen in this cell type in two carcinomas in pleomorphic adenomas, and also in a few cells in a pleomorphic adenoma and an adenoid cystic carcinoma. Thus the pattern of IFP expression in salivary gland neoplasms, is very complex, and cannot always be related to the normal tissue.

Subtyping of epithelial cells of normal and metaplastic human uterine cervix, using polypeptide-specific cytokeratin antibodies

The aim of the present study was to explore the histogenesis of metaplastic cells in the human uterine cervix. In a previous study we demonstrated that squamous cervical metaplasia expresses a unique set of cytokeratin polypeptides different from that expressed by the various normal epithelial elements of both the exo- and endocervix. It was thus proposed that the formation of squamous metaplasia represented a new route of differentiation. In the present study we further investigated this aspect by expanding the battery of monoclonal antibodies directed against specific cytokeratin epitopes used for immunohistochemical labelling. The antibodies used were: KS-1 A3, which specifically stains cytokeratin polypeptide no. 13; antibody KS-2.1, which is an anti-cytokeratin reacting with pseudostratified transitional and some simple epithelia; and antibody KS-B17.2 reacting with cytokeratin polypeptide no. 18. Examination of the staining patterns obtained with these antibodies revealed specific staining of ciliated cells with antibody KS-2.1 and of endocervical reserve cells with antibody KS-1A3. In 6 out of 19 cases tested reserve cells were also stained with antibody KS-2.1. These results enabled us to distinguish between at least four types of cells residing within the simple epithelium of the endocervix, namely columnar nonciliated cells, ciliated cells, and two subpopulations of reserve cells. Since metaplasia was positively stained by antibodies KS-1A3 and KS-2.1, we propose that the endocervical reserve cells that express cytokeratin polypeptide no. 13 are most probably the cells from which endocervical metaplasia is derived.

Monoclonal antibody mapping of keratins 8 and 17 and of vimentin in normal human mammary gland, benign tumors, dysplasias and breast cancer

The distribution of keratins 8 and 17 and of vimentin in 28 normal human mammary tissue samples, 16 benign tumors, 26 fibrocytic diseases and 52 malignant breast tumors have been studied using monoclonal antibodies HI, E3 and NT30, respectively. Three cell populations in normal mammary epithelium have been identified: luminal epithelium containing keratin 8, myoepithelium of the lobular structures positive for vimentin, and myoepithelium of extralobular ducts positive for keratin 17. In different kinds of benign tumor and dysplastic proliferation a mosaic of cells with all normal phenotypes has been observed. The majority of cells co-expressed keratins 8 and 17 or vimentin. In the overwhelming majority of carcinomas, cells did not contain myoepithelial markers (keratin 17 and vimentin) but expressed only keratin 8 specific to normal luminal epithelium.

Monoclonal antibody-detected vimentin distribution in pleomorphic adenomas of salivary glands

To evaluate the participation of myoepithelial components in pleomorphic adenomas, an immunohistochemical study was carried out using monoclonal antibodies to vimentin. Of a total of 80 cases, 50 tumors gave positive staining, 5 tumors very slight, and 25 tumors negative staining for vimentin. Localization patterns for vimentin were divided into 3 classes: 1) vimentin staining in fibrous stromal tissue; 2) variable intensities of vimentin staining were found in the outer layers of tumor cells in tubulo-ductal structures (some of which were spindle cells connected to modified myoepithelial cells which also gave variable vimentin staining); and 3) modified myoepithelial cells and chondroidlike cells displayed strongly positive staining for vimentin. Typical histologic features of pleomorphic ademomas, i.e., tubulo-ductal or duct-like structures were characterized by positive vimentin staining in outer tumor cells and by a positive keratin reaction in the luminal tumor cells. In tumors devoid of stromal connective tissues and the near absence of well-developed, or modified myoepithelial cells, vimentin staining was absent.

Distribution of intermediate filament proteins in developing and adult salivary glands in man

Adult and developing salivary glands were investigated using five monoclonal antibodies against cytokeratins (CKs) and vimentin. Acinar cells displayed mainly CK 18 whereas CKs 7, 17 and 19 were only detected in duct and myoepithelial cells. All epithelial and myoepithelial cells were unreactive for one vimentin antibody (Vim 9) whereas with the other (Vim 24), myoepithelial cells and basal cells of excretory ducts were stained. Fetal cells showed the CK pattern of duct cells. At gestational week 18, a reaction for both vimentin antibodies could be found in basal cells of terminal tubules. Although vim 9 reactivity has been shown for a number of salivary neoplasms, it has not been detected in any adult epithelial salivary tissue. The finding of this reactivity in the fetal gland indicates that the expression of this intermediate filament protein in certain salivary neoplasms may be a sign of dedifferentiation resulting in the expression of a filament pattern found in an earlier stage of gland development.

Immunohistochemical study of palatal salivary glands of denture wearing patients

The binding pattern of antibodies against different cytokeratin (CK) polypeptides, tissue polypeptide antigen (TPA), carcinoembryonic antigen (CEA), lactoferrin (Lf), lysozyme (Ly) and secretory component (SC) in palatal glands (PSG) of long-term denture wearing patients has been studied to investigate immunohistochemically the localization of these marker proteins in normal PSG and in denture-induced sialadenitis of PSG. The study included palatal gland biopsies from 28 patients (15 f, 13 m; mean age 59 years), 17 of them with normal PSGs, 8 with focal obstructive sialadenitis, and 3 with diffuse sialadenitis. Presence of CK and TPA was found in all intra- and extraglandular salivary ducts, in the basophilic portions of acini, in some mucous acini, and in all atrophic acini. Increased expression of CEA and Lf was observed in inflammed areas of PSG which, on the other site, were devoid of Ly and SC. In the mucous acini of healthy PSG considerable basal Ly immunoreactivity was seen. SC was localized in almost all ductal cells and in some acinar cells. Appearance of Lf in the ductal cells of PSG indicates an early sign of palatal sialadenitis. Some distinctions in the expression pattern of the marker proteins between the mucous acini of major salivary glands and PSG point to differences in the functional activities of either group of salivary glands.

Immunohistochemical localization of keratin, vimentin and myosin in salivary gland tumors

An immunohistochemical study on keratin, vimentin, and myosin was performed in 117 specimens of human salivary gland under normal and several neoplastic conditions. In normal glands, positive immunostaining for keratin was observed in the inner cells of all ductal systems, whereas myosin and vimentin were the cytoskeletal components of myoepithelial cells. In pleomorphic adenoma, the inner cells showing a tubular pattern demonstrated positive immunostaining for keratin, and the outer cells as well as the neoplastic cells with a solid and myxoid pattern exhibited positive immunostaining for all antibodies. Monomorphic tubular and trabecular adenoma, and adenolymphoma showed positive immunostaining for keratin, although one case of tubular adenoma exhibited positive immunostaining for all antibodies. Squamous cell carcinoma, adenosquamous carcinoma, and mucoepidermoid tumor showed positive immunostaining only for keratin, but one case of adenocarcinoma, two cases of adenoid cystic carcinoma, and clear cell tumor disclosed positive immunostaining for keratin and vimentin.

Expression of cytokeratins and vimentin in salivary gland carcinomas as revealed with monoclonal antibodies

The expression and distribution of cytokeratins and vimentin in fifteen malignant salivary neoplasms were examined by immunocytochemical techniques using, five monoclonal antibodies (mAbs) against different epitopes of Cytokeratins (CKs) (mAbs PKK1, PKK2, and PKK3, identifying CKs 8, 18 and 19, CKs 7, 17 and 19, and CK 18, respectively) and Vimentin (mAbs V9 and V24). Antibody PKK1 gave strong reactions in all neoplasms showing the similarity of these tumours to other digestive system adenocarcinomas. Three general staining patterns of the neoplasms were recognized with respect to the reactivity of mAbs PKK2, PKK3, and V9. Mucoepidermoid cancer, salivary duct carcinoma and a clear cell carcinoma had a higher relative content of CKs 7, 17 and 19 than of CK 18. Adenoid cystic carcinoma showed the same CK pattern but in the periphery of the tumour cords vimentin was readily detected. In two acinic cell carcinomas, the relative content of CK 18 was higher than that of CKs 7, 17 and 19. Furthermore vimentin was expressed in the tumour cells. However, one mucoepidermoid carcinoma showed vimentin expression and two acinic cell carcinomas were vimentin negative and more reactive for PKK2 than PKK3. Pecularities in CK expression were seen: squamous areas of mucoepidermoid carcinomas were stained by mAb PKK3 although CK 18 is not present in normal squamous epithelia or in squamous cell carcinomas of tongue and skin. In conclusion, the different salivary neoplasms can be distinguished on basis of IFP content. Such a differentiation fits with current theories of histogenesis, i.e. vimentin is seen in tumours presumed to arise from intercalated duct reserve cells, whilst the vimentin negative neoplasms would be expected to arise in excretory duct reserve cells.

Monoclonal antibodies to epithelial sialomucins recognize epitopes at different cellular sites in adenolymphomas of the parotid gland

Fourteen monoclonal antibodies (MAbs) to epithelial sialomucins were studied for their immunohistochemical reactivity on serial sections of 14 formalin-fixed and paraffin-embedded adenolymphomas of the parotid gland. Two types of reactivity were observed, suggesting different cellular distribution of the corresponding epitopes. Most antibodies reacted with the luminal membrane of the columnar tumor cells (type-A reaction). The other reaction (type B) was observed with the membrane of basal epithelial cells. The antibodies could be ranked according to their tendency to show type-A and/or type-B reactions. MAb Cal was the only one with a pure type-A reaction. A strong tendency to type-A reactivity (with traces of type-B reactions) was observed for the antibodies HMFG-2, M8, E29 and NCRC-II. Several antibodies gave good type-B reactions in addition to strong type-A reactivity (MAbs 126E7, 115G2, 115D8, 140C1, F36/22, 139H2). MAb DF3 showed equally strong reactions with both cell types. A clear-cut preference of the reactions with basal cells was seen with the antibodies HMFG-1 and 115F5. This subclassification of the antibodies is in accordance with epitope mapping data, obtained by conventional blocking studies reported in the literature.

Distribution of cytoskeletal and contractile proteins in normal and tumour bearing salivary and lacrimal glands

We have evaluated by means of immunocytochemistry the distribution of various cytoskeletal and contractile proteins (cytokeratins, vimentin, desmin and alpha-smooth muscle actin) in 23 salivary or lacrimal gland primary tumours (15 pleomorphic adenomas and 8 carcinomas in pleomorphic adenoma), one third of which contained areas of normal gland. Normal epithelial luminal cells were stained by cytokeratin antibodies with a general specificity, while myoepithelial cells were selectively stained by a monoclonal antibody (SK2-27) reacting in immunoblots with cytokeratin polypeptides 14, 16 and 17, according to the classification of Moll et al. (1982) and by an antibody directed against alpha-smooth muscle actin (Skalli et al. 1986). In pleomorphic adenomas, both epithelial and myoepithelial cells displayed typical topographic distributions; moreover, myoepithelial cells showed two distinct cytoskeletal phenotypes. These findings could account in part for the heterogeneity of aspects observed in this tumour. In carcinomas, malignant cells were always positive to cytokeratin antibodies with general specificity and myoepithelial cells were absent as judged by anticytokeratin SK2-27 and anti-alpha-smooth muscle actin immunostainings. However, interestingly, there was in all cases a strong positivity for alpha-smooth muscle actin in stromal cells, similarly to what has previously been described for mammary carcinoma (Skalli et al. 1986). Our findings may be useful for the interpretation of the histogenesis of salivary and lacrimal tumour and stromal cells.

The cellular composition of adenoid cystic carcinoma. An immunohistochemical study

To investigate the cellular differentiation of adenoid cystic carcinomas (ACC), a comparative immunohistochemical study of 12 normal salivary glands and eight specimens of ACC was performed. Antibodies were used against S100 protein (S), keratins (K) of various molecular weights, vimentin (V), muscle-specific actin (A), epithelial-membrane antigen, human milk fat globules, and collagen type IV. A panel of four of these antibodies (SKVA) was identified as the most helpful in characterizing cells in normal salivary glands and ACC. The immunophenotypes depended on the histologic patterns of ACC. Cells in morphologically recognizable duct structures in the cribriform and trabecular areas expressed a phenotype similar to that of the intercalated duct. Cell layers around pseudocysts and occasional cellular islands had an immunophenotype suggesting myoepithelial-cell differentiation. The most clear cut epithelial/myoepithelial bilaminar differentiation was present in areas with a trabecular pattern, in which the layers facing the stroma and the central ductal elements had SKVA phenotypes of myoepithelial and ductal differentiation, respectively. In areas with a reticular pattern, most of the cells showed ductal differentiation. Many of the cells in the cribriform and basaloid regions were immunophenotypically undifferentiated. These results indicate that ACC consists of undifferentiated cells and of cells that are differentiating toward ducts, predominantly intercalated ducts, and toward myoepithelium. These findings support previous observations by electron microscope.