Cytokeratin polypeptides expression in different epithelial elements of human salivary glands

Phenotype and cell proliferation activity of duct-like structures in human sublingual glands: a histological and immunohistochemical study

There are several age-related microscopic changes in the salivary glands, including the increase in the number of duct-like structures (DLS). However, the true origin and the phenotype of the DLS are not known.

Oral cytokeratins in health and disease

The dynamics of oral mucosa is known by its inherent defensive nature. Certain areas demand tough shield when subjected to mechanical insults. This is met by structural scaffolding material referred as cytoskeleton comprised of intracellular protein filaments called cytokeratins in the surface squames of oral epithelia. They also equally contribute towards the architecture of odontogenic apparatus and salivary gland. Differentiation of epithelial cells within stratified epithelia regulates the expression of specific keratin gene. Any mutation in, or autoantibodies to keratins, desmosomal and cornified envelope proteins is translated into genetic and acquired human disorders. Sound knowledge of structural proteins, their expression, distribution and function plays a vital role in acquainting with these disorders and their application as differentiation markers. Thus, they form an integral aid in diagnostic pathology and may be instrumental in the future interventions by gene therapy. This review focuses on basics to current updates on oral cytokeratins with an emphasis on the genetic and acquired disorders of cytokeratins with oral implications.

Interlobular excretory ducts of mammalian salivary glands: structural and histochemical review

In the major salivary glands of mammals, excretory ducts (EDs) succeed striated ducts. They are for the most part interlobular in position, although their proximal portions sometimes are on the periphery of a lobule, where they occasionally retain some of the structural features of striated ducts. Based on a survey of a broad range of mammalian species and glands, the predominant tissue type that composes EDs is pseudostratified epithelium. In some species, there is a progression of epithelial types: the proximal EDs are composed of simple cuboidal or columnar epithelium that, in the excurrent direction, usually gives way to the pseudostratified variety. Secretory granules are visible in the apical cytoplasm of the principal cells of the EDs of only a few species, but histochemistry has shown the presence of a variety of glycoproteins in these cells in a spectrum of species. Moreover, the latter methodology has revealed the presence of a variety of oxidative, acid hydrolytic, and transport enzymes in the EDs, showing that, rather than simply acting as a conduit for saliva, these ducts play a metabolically active role in gland function. It is difficult to describe a "typical" mammalian ED because it can vary along its length and interspecific variation does not follow a phylogenetic pattern. Moreover, in contrast to intercalated and striated ducts, ED cellular features do not exhibit a relationship to diet.

Ductal Metaplasia in Chronic Lymphocytic Thyroiditis as a Manifestation of Phylogenic Regression to an Exocrine Structure

From a morphologic and functional point of view the thyroid can be considered as both an exocrine and endocrine organ. Firstly, thyroglobulin is secreted at the apical pole of the thyrocyte. Secondly, after endocytosis thyroglobulin is lysed and T3 and T4 are secreted at the basal pole into the bloodstream. However, usually exocrine glands are constituted of 2 well separate components: an acinus/alveolar component and an exocrine duct component. Under particular conditions such as chronic injury the acinus/alveolar component is rapidly destroyed, whereas the ductal component seems to be far more resistant and can proliferate giving rise to a tubular network described as "ductulus reaction" or "ductal metaplasia." Normal exocrine ducts and metaplastic ducts exhibit common genetic and phenotypic features directly related to their tubular morphology. In this study, we describe in lymphocytic autoimmune thyroiditis the appearance of ductal-like structures which displayed the features of ductal metaplasia.

Differential diagnosis of salivary acinic cell carcinoma and adenocarcinoma (NOS). A comparison of (immuno-)histochemical markers

A correct histologic differential diagnosis between salivary acinic cell carcinoma (ACC) and adenocarcinoma not otherwise specified (AC-NOS) is highly relevant because of the strikingly different biologic behavior and related therapeutical strategies. The distinction between both tumor types can be difficult because of an enormous variation in histologic appearance, with either type showing partially overlapping morphologic features. Owing to a lack of approved markers, the expression of PAS-staining, alpha-Amylase, alpha-1 Anti-trypsin, cytokeratin (CK)-subtypes 7/18 and Ki-67 was evaluated in 16 cases of ACC and 16 cases of AC-NOS. CK 7 is identified as the most reliable marker with strong positivity in AC-NOS, and complete or preponderant negativity in ACC. The characteristic membranous staining pattern of CK 18 in ACC, in contrast to a diffuse cytoplasmic pattern in AC-NOS, proved to be an additional valuable criterion. PAS and alpha-Amylase are only of little value when ACC is diagnosed, as many cases are only faintly positive or completely negative. The proliferation index (Ki-67) proved to be significantly higher in AC-NOS; however, the diagnostic usefulness is limited by a relevant overlap. In conclusion, we recommend CK 7 and 18 as the most valuable markers in cases with difficult differential diagnosis between ACC and AC-NOS.

Immunocytochemistry of myoepithelial cells in the salivary glands

MECs are distributed on the basal aspect of the intercalated duct and acinus of human and rat salivary glands. However, they do not occur in the acinus of rat parotid glands, and sometimes occur in the striated duct of human salivary glands. MECs, as the name implies, have structural features of both epithelial and smooth muscle cells. They contract by autonomic nervous stimulation, and are thought to assist the secretion by compressing and/or reinforcing the underlying parenchyma. MECs can be best observed by immunocytochemistry. There are three types of immunocytochemical markers of MECs in salivary glands. The first type includes smooth muscle protein markers such as alpha-SMA, SMMHC, h-caldesmon and basic calponin, and these are expressed by MECs and the mesenchymal vasculature. The second type is expressed by MECs and the duct cells and includes keratins 14, 5 and 17, alpha 1 beta 1 integrin, and metallothionein. Vimentin is the third type and, in addition to MECs, is expressed by the mesenchymal cells and some duct cells. The same three types of markers are used for studying the developing gland. Development of MECs starts after the establishment of an extensively branched system of cellular cords each of which terminates as a spherical cell mass, a terminal bud. The pluripotent stem cell generates the acinar progenitor in the terminal bud and the ductal progenitor in the cellular cord. The acinar progenitor differentiates into MECs, acinar cells and intercalated duct cells, whereas the ductal progenitor differentiates into the striated and excretory duct cells. Both in the terminal bud and in the cellular cord, the immediate precursors of all types of the epithelial cells appear to express vimentin. The first identifiable MECs are seen at the periphery of the terminal bud or the immature acinus (the direct progeny of the terminal bud) as somewhat flattened cells with a single cilium projecting toward them. They express vimentin and later alpha-SMA and basic calponin. At the next developmental stage, MECs acquire cytoplasmic microfilaments and plasmalemmal caveolae but not as much as in the mature cell. They express SMMHC and, inconsistently, K14. This protein is consistently expressed in the mature cell. K14 is expressed by duct cells, and vimentin is expressed by both mesenchymal and epithelial cells. After development, the acinar progenitor and the ductal progenitor appear to reside in the acinus/intercalated duct and the larger ducts, respectively, and to contribute to the tissue homeostasis. Under unusual conditions such as massive parenchymal destruction, the acinar progenitor contributes to the maintenance of the larger ducts that result in the occurrence of striated ducts with MECs. The acinar progenitor is the origin of salivary gland tumors containing MECs. MECs in salivary gland tumors are best identified by immunocytochemistry for alpha-SMA. There are significant numbers of cells related to luminal tumor cells in the non-luminal tumor cells that have been believed to be neoplastic MECs.

Expression of cytoskeletal proteins in developing human minor salivary glands

The presence of an epithelium at different stages of proliferation and differentiation raises interesting questions concerning the histogenesis, cell turnover and differentiation of normal salivary glands. In order to expand knowledge of these aspects, we investigated the expression of cytokeratins (CKs) 7,8,10,13,14,16,18 and 19, vimentin (VIM), and smooth muscle actin (SMA) in developing human minor salivary glands using monoclonal antibodies. Labial, buccal, palatine, and lingual salivary glands and those from the floor of the mouth were obtained from human fetuses (forensic postmortem) ranging in age from gestational weeks 10 to 29. Serial sections, 3 microm thick, were immunostained using a strepto-avidin-biotin technique. Reactivity for all antibodies was negative in the salivary gland epithelium during the developmental stages of bud formation, cord growth, and branching of cord. During canalization and cytodifferentiation, the glandular epithelial cells showed a positive reaction to some CKs and SMA. Cytokeratins 7, 8, 18, and 19 showed strong labeling in luminal duct cells that exhibited some degree of morphological differentiation. Myoepithelial cellc were recognized by antibodies to SMA. Cytoskeletal protein expression changes according to the cell type, degree of differentiation, and stage of morphological development of the glandular structure. These changes occur independently of the localization of the gland.

Ion transport in an immortalized rat submandibular cell line SMG-C6

The immortalized rat submandibular epithelial cell line, SMG-C6, cultured on porous tissue culture supports, forms polarized, tight-junction epithelia facilitating bioelectric characterization in Ussing chambers. The SMG-C6 epithelia generated transepithelial resistances of 956+/-84Omega.cm2 and potential differences (PD) of -16.9 +/- 1.5mV (apical surface negative) with a basal short-circuit current (Isc) of 23.9 +/- 1.7 microA/cm2 (n = 69). P2 nucleotide receptor agonists, ATP or UTP, applied apically or basolaterally induced a transient increase in Isc, followed by a sustained decreased below baseline value. The peak DeltaIsc increase was partly sensitive to Cl- and K+ channel inhibitors, DPC, glibenclamide, and tetraethylammonium (TEA) and was completely abolished following Ca2+ chelation with BAPTA or bilateral substitution of gluconate for Cl-. The major component of basal Isc was sensitive to apical Na+ replacement or amiloride (half-maximal inhibitory concentration 392 nM). Following pretreatment with amiloride, ATP induced a significantly greater Isc; however, the poststimulatory decline was abolished, suggesting an ATP-induced inhibition of amiloride-sensitive Na+ transport. Consistent with the ion transport properties found in Ussing chambers, SMG-C6 cells express the rat epithelial Na+ channel alpha-subunit (alpha-rENaC). Thus, cultured SMG-C6 cells produce tight polarized epithelia on permeable support with stimulated Cl- secretory conductance and an inward Isc accounted for by amiloride-sensitive Na+ absorption.

Application of immunohistochemistry to the diagnosis of salivary gland tumors

A panel of antibodies composed of the cytokeratins (CKs), vimentin, and actin was applied to 114 minor salivary gland tumors to evaluate its diagnostic value. The results revealed that luminal cells of intercalated duct-like structures, such as those seen in pleomorphic adenoma, basal cell adenoma, adenoid cystic carcinoma, and epithelial-myoepithelial carcinoma, expressed CKs 7, 8, 14, and 19. The outer cells of these structures exhibited vimentin or vimentin plus muscle-specific actin, but rarely CK14, which is seen particularly in pleomorphic adenoma, in the tubular type of basal cell adenoma, and seldom in the tubular type of adenoid cystic carcinoma. Modified myoepithelial cells of pleomorphic adenoma and myoepithelioma exhibited a variable immunoprofile. CKs 7 and 8 were also observed in acinar cell adenocarcinoma and polymorphous low-grade adenocarcinoma with vimentin in the latter. CK13 was expressed only by canalicular adenoma and mucoepidermoid carcinoma cells. This study showed that the panel of antibodies employed is effective in distinguishing among salivary gland tumors.

Mucinous adenocarcinoma of the sublingual gland

A case of mucinous (colloid) adenocarcinoma of the sublingual gland is reported. Adenocarcinomas associated with large pools of extracellular mucin are extremely rare in the major salivary glands. Analysis of the tumor for cytokeratin expression, estrogen and progesterone receptors was performed. Predominantly, the tumor expressed cytokeratins 7, 8, 18 and 19 that are commonly found in simple epithelia, and to a lesser degree cytokeratins 4 and 13 which are usually found in complex epithelia. Staining for estrogen and progesterone receptors was negative. No other cancer has been detected for three years after the first examination. The tumor is considered to be a primary mucinous adenocarcinoma of the sublingual gland.

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.

Immortalised mouse submandibular epithelial cell lines retain polarised structural and functional properties

The mouse submandibular gland (SMG) is an excellent model for the study of many important biological phenomena such as hormonal regulation of differentiation, neurotransmitter control of secretion, epithelial transport, exocytosis and endocytosis as well as the regulation of mouse SMG specific gene expression, in particular, NGF, EGF and renin. The postnatal development and sexual dimorphism of the mouse gland permits the isolation of male SMGs of different ages, corresponding to different stages of differentiation, particularly with respect to the cytodifferentiation of ductal cell types. We have immortalized SMG epithelial cell lines using mice transgenic for the large T antigen of SV40 or polyoma viruses. Epithelial clusters from the dissected glands were placed in culture and cell lines were established from the immortalized population. Two cell lines, SIMS and SIMP, which retain structural and functional characteristics, are described here. The cell lines are immortalised but not transformed, as judged by the absence of anchorage independent growth potential and the lack of tumour formation in athymic nude mice. Confocal and electron microscopy examination demonstrate that SIMP and SIMS cells express E-cadherin and ZO-1 and have features of polarised epithelial cells. In addition, they form spherical cysts with a wide lumen when grown in type I collagen gels. When grown on a filter support SIMS cells form a tight monolayer, exhibit vectorial transport function and show exclusive Na+, K(+)-ATPase localisation to the basolateral domain. We determined the cell type restricted expression of cytokeratin markers in the mouse SMG in vivo and we demonstrate that SIMS and SIMP cell lines express duct-specific cytokeratins. Finally, the expression of a set of differentiation markers, including EGF, NGF and renin, was detected by RT-PCR and by indirect immunofluorescence staining in these lines. Thus, these polarised ductal cell lines, as well as having important intrinsic properties, represent well characterised mouse epithelial models which, until now, have not been readily available for cellular studies.

Sialadenoma papilliferum: an immunohistochemical study of five cases

Sialadenoma papilliferum (SP) is a rare, benign, salivary gland tumor which most commonly arises in the palate. It has a typical biphasic gross and microscopic appearance which distinguishes this tumor from other papillary-like tumors of the oral cavity. This study reports the clinico-pathologic features of 5 new cases and analyzes the morphologic and immunophenotypic features of their cell components. Adluminal epithelial cells of duct-like structures appeared immunoreactive to cytokeratin 19 and to S-100 protein antibodies; two subsets of basally-located cells were identified by means of immunohistochemistry. One cell subset expressed cytokeratin 14, S-100 protein, GFAP, vimentin and smooth muscle actin immunoreactivity; this antigenic profile is consistent with myoepithelial differentiation. The second subset of basal cells expressed cytokeratins 13 and 14 reactivity but it was negative to all other antibodies. Anti-CD 1a and anti-S-100 protein antibodies revealed distinct cells with dendritic processes which resembled Langerhans cells. The extralobular location of SP, the continuity between neoplastic duct-like structures and the surface epithelium along with the presence, within the excretory ducts adjacent to the tumour, of lesions which possibly precede the development of SP give further strength to the hypothesis of an origin from the excretory ducts of this tumor. Langerhans cells seem to be present in sialadenoma papilliferum but their role in this tumor is still unclear.

Expression of different keratins in salivary gland tumours

Twenty-four salivary gland tumours (six pleomorphic adenomas, two myoepitheliomas, five basal cell adenomas, six adenoid cystic carcinomas and five polymorphous low grade adenocarcinomas) were investigated by an immunocytochemical technique using monoclonal antibodies against cytokeratins (CKs) 7, 8, 10, 13, 14, 18 and 19. The luminal cells of ductal structures of the tumours reacted with all the CKs studied except for CK 13 and CK 10 and sometimes CK 14, showing an immunoprofile comparable to that of the intercalated segment of a normal salivary gland. The outer cells of the ducts rarely stained with CK 14, confirming that full differentiation of the myoepithelial cells is seldom achieved in tumours. Considerations were made regarding the intriguing expression of CK 14, the heterogeneous expression of CKs in the modified myoepithelial cells and the immunoprofile of the polymorphous low-grade adenocarcinoma.

Myoepithelioma: definitions and diagnostic criteria

Due to their infrequency and multiplicity of histopathology, myoepitheliomas present difficulties in diagnosis and classification. Cellular varieties can be misdiagnosed as malignancies. Improvements in and clarification of diagnostic criteria are, therefore, required. A key to determining diagnostic criteria for myoepitheliomas is to study cellular morphology, cytoplasmic filament expression, and ultrastructural features of the nonluminal, i.e., neoplastic myoepithelial/basal, tumor cells of pleomorphic adenomas, and apply this information to defining myoepitheliomas. Cytologic and growth patterns of nonluminal cells in pleomorphic adenomas, including plasma-cytoid cells, are reflected in myoepitheliomas. Results also indicate that muscle-specific actin and myofilaments are expressed only in a proportion of cases, and generally in not more than 60-70% of nonluminal cells in pleomorphic adenoma; this also applies to benign and malignant myoepitheliomas. The absence of these markers does not exclude a diagnosis of myoepithelioma. Vimentin and glial acidic fibrillary protein, however, are strongly and diffusely expressed in the majority of pleomorphic adenomas and myoepitheliomas and are more reliable markers for these tumors than muscle-specific actin. Like so many other salivary gland tumors, myoepitheliomas present an equally complex histomorphology and variable expression of antigenic markers, only some of which are associated with myoepithelial and basal cells of the acini and ducts of the normal salivary gland.

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.

Cytokeratin patterns of normal middle ear epithelia in humans, cats, and chinchillas

We describe the cytokeratin patterns of epithelia from the tympanic orifice, tympanic cavity, and mastoid cavity of humans, cats, and chinchillas, and compare these findings with those of tracheal epithelium and external canal epidermis. Our findings are as follows: 1) middle ear epithelium from all locations demonstrates some type of cytokeratin staining, 2) broad-spectrum cytokeratin antibodies stain epithelia of middle ear cleft, tracheal epithelium, and external canal epidermis in all species, 3) specific cytokeratin antibodies reveal species-related differences in middle ear and tracheal epithelia, 4) middle ear and tracheal epithelia usually have the same pattern, and 5) none of the monospecific cytokeratin antibodies have a positive reaction with external canal epidermis. These findings suggest that the cytokeratin patterns of middle ear epithelium are useful in studying the hyperplastic and metaplastic changes in otitis media; however, caution must be exercised when making interspecies comparisons.

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.

A model to study viral and cytokine involvement in Sjögren's syndrome

To investigate mechanisms that may be important in the pathogenesis of Sjögren's syndrome (SS) we developed a protocol for the growth of salivary gland epithelial cells in culture. We examined the effect that viral infection has on the cellular location of the autoantigen La. Autoantibodies to La are common in SS and it has been proposed that viral infection may result in cell membrane expression of La. Co-expression of MHC class II molecules in infected cells could lead to the presentation of La peptides to the immune system. Advenovirus infection of salivary gland epithelial cells resulted in an altered nuclear staining of La. Treatment with interferon-gamma resulted in the expression of La in the cell cytoplasm and HLA-DR molecules at the cell surface. These findings suggest that a cytokine-driven mechanism may generate an autoimmune response to La in SS. Using the polymerase chain reaction (PCR) we tested salivary gland epithelial cell cultures for the presence of human herpesvirus-6 (HHV-6) and Epstein-Barr virus (EBV). Only HHV-6 was detected in 2 of 10 salivary gland epithelial cell cultures although the presence of HHV-6 was not associated with SS. Primary salivary gland cultures may prove useful as an in vitro model to study mechanisms of autoimmunity in SS.

Monoclonal antibody to liver metallothionein: a novel marker for myoepithelial cells

Myoepithelial cells (MEC) are situated between acinar or ductal luminal cells and the basal lamina in various secretory glands, including salivary gland. The in-situ demonstration of MEC in benign and malignant conditions has long been hampered by the lack of suitable markers, most of which do not label MEC exclusively. We report here the reactivity of L2E3, a monoclonal antibody directed against liver metallothionein (MT). In the major and minor salivary glands, L2E3 stained two types of cells: a slender, elongated cell that surrounded acini; and a small, basal, cuboidal cell observed in the excretory (interlobular) ducts. Our results indicate that L2E3 represents a novel, useful marker for the immunohistochemical identification of MEC, and a highly sensitive marker for ductal basal or "reserve" cells in salivary glands.

Expression of keratin mRNAs and proteins in normal salivary epithelia and pleomorphic adenomas

Control of keratin (K) gene expression may be important for cell differentiation in complex epithelia such as salivary gland. To investigate differences in distribution between keratin mRNAs and their respective proteins, a combined in situ hybridization (ISH) and immunohistochemical study was undertaken on nine normal salivary glands and seven pleomorphic adenomas. ISH employed riboprobes to K7, K8, K14, K18, and K19. Immunohistochemistry was performed on adjacent sections using monoclonal antibodies (MAbs) to the same keratins. Normal luminal cells showed abundant hybridization with probes for K7, K8, K18, and K19. Keratin 14 mRNA was present in basal and myoepithelial cells at a low level of expression. Proteins of their keratins were strongly stained. Neoplastic cells showed variable expression of mRNA and protein for K7, K8, K18, and K19. There was a high level of K14 mRNA but variable protein. The findings provide evidence that expression of these keratins in normal salivary epithelia is regulated transcriptionally and that in neoplasia this system is in considerable disarray.

Current status of histogenetic and morphogenetic concepts of salivary gland tumorigenesis

Because of their complexity and relative infrequency, salivary gland tumors commonly result in diagnostic problems. Histogenetic and morphogenetic concepts of tumorigenesis in these glands are reviewed and their relevance to routine diagnosis and classification of salivary gland tumors evaluated. Evidence is presented from animal and human studies that under steady-state and pathophysiological conditions, all cell types present in the normal gland, including acinar cells, are capable of rapidly entering the cell cycle and are, therefore, possible targets for neoplastic transformation.

Immunohistochemical staining of tenascin in Warthin's tumor and in oncocytoma

The presence of tenascin was studied immunohistochemically in Warthin's tumor and in oncocytoma. In Warthin's tumor this extracellular matrix protein was seen in the proximity of the basement membrane zone beneath the oncocytic epithelium, in the proximity of the basement membrane of venules and of high endothelial venules, and in the reticular tissue of the lymphoid stroma. Type IV collagen was seen in the same areas as tenascin. Fibronectin was also seen in areas similar to those of tenascin and in the adjacent stroma. Tenascin was found in oncocytoma as a focal staining, and fibronectin was seen around the basement membrane and adjacent stroma. Type IV collagen was seen as a distinct staining along the basement membranes. Although the oncocytic epithelial cells in Warthin's tumor and in oncocytoma are thought to be actively proliferating cells, these two tumors differ in tenascin expression.

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.

Immunohistochemical analysis of the cytokeratin expression in middle ear cholesteatoma and related epithelial tissues

Immunohistochemical investigations were carried out to determine the pattern of cytokeratin (CK) expression in middle ear cholesteatoma and related epithelia. Using monoclonal antibodies specific for CK chains and the indirect immunoperoxidase technique, we examined 10 CK polypeptides for expression. The external stratified squamous epithelium of the tympanic membrane generally expressed CKs 5, 10, and 14. In addition, basal keratinocytes in the annular region of the pars tensa expressed CK 19 (a simple epithelium marker), while suprabasally the hyperproliferative marker CK 16 was expressed. These data reflect the unusual proliferative nature of this region. The unexpected appearance of CK 16 (known to have a limited distribution in healthy epidermis) clearly relates to its expression in the neighboring deep meatus. The medial simple epithelium of the eardrum revealed mucosal CKs 7, 8, 14, 18, and 19. Acquired cholesteatoma lesions, besides CKs 5, 10, and 14, consistently expressed CK 16 in suprabasal layers. These results constitute the first direct molecular evidence for the hyperproliferative nature of the cholesteatoma matrix. Overall, our CK data suggest that aural cholesteatoma lesions and epidermal tissue in this area are related. However, they do not explain the mechanism(s) by which the eardrum or meatal epithelia might invade the middle ear cavity. Congenital cholesteatomas expressed CKs 5, 10, 14, and 16 equally. These CK data do not support the idea of a metaplastic origin from middle ear mucosa; instead, they suggest activation of an ectodermal rest in the middle ear cavity.

Malignant myoepithelioma of minor salivary gland origin

Myoepithelial cells are a significant component of most types of salivary gland tumors. A small but increasing number of case reports have also shown that true myoepithelioma (ME) forms a distinct clinicopathologic entity of salivary gland tumors with unique histologic features, however, the malignant type of ME is exceedingly rare. The present paper reports a case of malignant ME originating from the palatal minor salivary gland. The patient was a 70-year-old Japanese male with recurrent tumor of the palatal region. Pathologically, the tumor consisted of proliferating polygonal-shaped cells and plump spindle cells with cellular atypia and frequent mitoses, forming lumen-less lobuli or strands. Clear tumor cells were also found in part. The stroma was poorly developed without any myxoid or chondroid features. Immunohistochemical study showed positive stainings for S-100 protein, actin and vimentin in the tumor cells. Ultrastructurally, tumor cells had features of myoepithelial cells.

Immunohistochemistry with keratin and smooth muscle actin monoclonal antibodies in canine digestive tract and extramural glands

The canine digestive system and its extramural glands (parotid gland, liver, pancreas) were immunohistochemically studied using a panel of twelve monoclonal antibodies (MoAbs) specific for human keratin proteins and for alpha-smooth muscle actin. Various epithelial tissues and cells were characterized by different keratin staining patterns. So, the epithelial lining of the upper alimentary tract was characterized by staining with the MoAb 6B10, specific for keratin-type (K) 4, and the absence of staining with the MoAbs directed against K 8 and 18 (CAM 5.2 and RGE 53, DE-K18 respectively), whereas the lower alimentary tract epithelium was not labeled by 6B10, but stained by the latter MoAbs. In the salivary glands the luminal and basal cells of the adenomeres as well as the different ductal structures could be immunohistochemically differentiated. The duct epithelium in liver and pancreas showed next to keratin staining characteristics in common with hepatocytes and exocrine pancreatic cells, additional staining by several keratin MoAbs. The keratin staining patterns in the canine tissues showed, in addition to similarities also distinct discrepancies when compared to the staining patterns in corresponding human tissues. Myoepithelial cells in salivary and oesophageal glands could be differentiated from other basally located epithelial cells by their exclusive immunoreactivity for alpha-smooth muscle actin. Canine pancreatic endocrine cells were not labeled by any of the keratin MoAbs. It is concluded that immunohistochemistry with polypeptide specific MoAbs specific for human keratin-types can be used to differentiate between different types of canine epithelial tissues and epithelial cells in the digestive tract. As a result such reagents may find their application in developmental biology and pathology of this species.

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.

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.

Immunocytochemical characterization of lung tumors in fine-needle aspiration. The use of cytokeratin monoclonal antibodies for the differential diagnosis of squamous cell carcinoma and adenocarcinoma

In the current study, immunocytochemical typing of intermediate filaments was used for a differential diagnosis of human lung tumors from transthoracic fine-needle aspiration biopsies (TFNAB). The authors have compared the cytologic diagnosis of 53 lung cancer cases with the immunofluorescence patterns obtained using a panel of monoclonal antibodies, five of which (KG 8.13, KM 4.62, Ks B.17, KS 8.12, KK 8.60) react with specific cytokeratin polypeptides and one with vimentin (VIM 13.2). Only in six of 23 samples cytologically diagnosed as squamous cell carcinoma did the immunocytochemical typing of cytokeratins (ICTC) confirm the cytologic diagnosis. In seven cases some of the tumor cells stained positively with antibody Ks B.17 specific for simple epithelial keratin (No: 18), suggesting the presence of some cells of glandular origin. In ten additional cases the ICTC was in conflict with the cytologic diagnosis of squamous cell carcinoma (i.e., antibodies Ks 8.12 and KK 8.60 were negative, and antibody Ks B.17, positive) supporting a diagnosis of adenocarcinoma. In 14 of 18 cases cytologically diagnosed as adenocarcinoma, the ICTC confirmed the diagnosis whereas in four cases additional presence of some squamous cells was noticed. The ICTC labeling of cases cytologically diagnosed as undifferentiated and large cell carcinomas was similar to that of the group of adenocarcinomas. Thus, the application of cytokeratin typing for TFNAB samples seems to provide a vital complementation to routine cytologic study, especially for cases cytologically diagnosed as squamous carcinoma.

Comparative histogenesis and morphogenesis of mucoepidermoid carcinoma and pleomorphic adenoma. An ultrastructural study

Current classifications of salivary gland tumors separate mucoepidermoid carcinoma from other neoplasms on the basis of a number of histological features, in particular the lack of participation of neoplastic myoepithelial cells. However, ultrastructural examination of low- and intermediate-grade mucoepidermoid carcinomas and pleomorphic adenomas reveals many common organizational and cellular features. Of prime importance is the relationship of intermediate cells to the luminal cells in mucoepidermoid carcinomas, which is remarkably similar to that seen between modified myoepithelial cells and luminal cells in pleomorphic adenomas. The results suggest that intermediate cells of mucoepidermoid carcinoma are the counterpart of the modified myoepithelial cells of pleomorphic adenoma. The generally accepted hypothesis that the former tumor develops from an excretory duct reserve cell, while the latter originates from an intercalated duct stem cell does not seem to be valid; pleomorphic adenoma and mucoepidermoid carcinoma appear to be closely related morphologically.

Regulation of vimentin expression in cultured human mammary epithelial cells

Using five different monoclonal antibodies to vimentin, we have examined the expression of vimentin in cryostat sections and serum-free cultures of normal human breast tissue. In cryostat sections, myoepithelial cells as well as stromal cells showed immunoreactivity to vimentin, irrespective of the antibody used. In contrast, luminal epithelial cells were negative for vimentin, but positive for keratin K18. In culture, myoepithelial cells showed immunoreactivity to vimentin from their first appearance in monolayer. Moreover, a fraction of luminal epithelial cells expressed vimentin in addition to keratin K18. We found a clear, reversible correlation between proliferation, determined by incorporation of [3H]-TdR, and induction of vimentin in the luminal epithelial cells. Thus, in growth-stimulated cultures on a medium containing cholera toxin (CT), epidermal growth factor (EGF), transferrin (Tf), hydrocortisone (H) and insulin (I), the fraction of vimentin-positive luminal epithelial cells increased, while it decreased within 14 days from approximately 36% to 3% on a medium containing CT and EGF, only. We therefore conclude: (1) vimentin is constantly expressed in myoepithelial cells in situ and in vitro, and (2) expression of vimentin in luminal epithelial cells in vitro is not a result of monolayer cultivation as such, but rather associated with the increased growth rate seen in culture.

Basal epithelial cells of human prostate gland are not myoepithelial cells. A comparative immunohistochemical and ultrastructural study with the human salivary gland

The hypothesis that basal epithelial cells of the human prostate are of myoepithelial origin was investigated using immunohistochemical and ultrastructural methodologies. The immunohistologic analyses show significant phenotypic differences between prostatic basal cells and myoepithelial cells of the salivary gland. Although both cell types stain intensely with the 312C8-1 monoclonal antibody, only true myoepithelial cells demonstrated significant amounts of muscle-specific actin as decorated by the HHF35 monoclonal antibody. Furthermore, using double-labeling experiments, the prostatic basal cells were strongly decorated with a fluorescein-tagged basal cell-specific keratin but were negative with the rhodamine-tagged phalloidin, a chemical that binds specifically to actin microfilaments. Ultrastructural studies also showed an absence of thin microfilament bundles, dense bodies, and micropinocytotic vesicles in the prostatic basal cells. The current investigations show that the prostatic acini do not have a basal myoepithelium. Although some authors have suggested a stem cell role for prostatic basal cells, the weight of experimental work argues against this hypothesis. The exact role of the basal epithelial cells of the prostate is not known, although they may serve endocrine, paracrine, or other regulatory functions and may be involved in modulating signals between prostatic stroma and epithelium.

Two-colour immunofluorescence marker study of pleomorphic adenomas

Extensive use of two-colour immunofluorescence staining for various cell markers in pleomorphic adenoma, revealed three consistent phenotypic features: (1) keratin polypeptide No. 14, which was virtually restricted to myoepithelial cells (MEC) in normal salivary glands, appeared in a large fraction of the tumour cells, suggesting that the principal neoplastic element is derived from MEC or their immediate precursors; (2) a complex co-expression pattern of various cell markers was found, with extensive concurrence of keratin and vimentin in strands of MEC-like and myxoid tumour cells, probably reflecting different degrees of tumour cell differentiation; and (3) two phenotypically distinctive dendritic cell populations were identified, one consisting of keratin positive tumour cells and the other of HLA-DR positive but keratin negative stromal cells. The significance of these findings with regard to the histogenesis and complex morphology of pleomorphic adenoma is discussed.

A review of the proliferative capacity of major salivary glands and the relationship to current concepts of neoplasia in salivary glands

The classification of salivary gland tumors relies heavily on histogenetic postulates. One of these, the semipluripotential reserve cell theory, suggests that certain reserve cells in specific segments of the duct system of major and minor salivary glands are critical to the development of neoplasms in these glands. However, direct evidence in support of this hypothesis is unavailable. This survey of proliferative capacity in normal salivary gland is based on a review of data in the literature, our observations of DNA synthetic and mitotic activity in developing rat and human salivary gland, and autoradiographic studies of induced cell proliferation in rat salivary gland. Autoradiography of neonatal rat salivary gland after tritiated thymidine administration, and electron microscopy of these tissues, reveals that as well as duct basal cells, luminal cells at all levels of the duct system and even acinar cells are capable of DNA synthesis and mitosis. Indeed, in such studies, more luminal than basal cells are seen in mitosis. In adult rat salivary gland induced to undergo hyperplasia, more acinar cells than intercalated duct cells are in the S phase of the cell cycle. However, cycling cells were observed even in striated ducts and, importantly, both basal and luminal cells of major interlobular excretory ducts are also labeled. Similar findings are present in fetal and adult human salivary glands. From such observations, it is evident that dividing cells are not limited to basal cells of excretory ducts and luminal cells of intercalated ducts, so that there is no support for the semipluripotential bicellular reserve cell hypothesis. However, there is considerable evidence for a multicellular theory of tumor histogenesis; that is, any of the multiplicity of cell types in normal salivary gland have the potential to give use to any of the various types of tumor occurring in this organ.

Prenatal development of human major salivary glands and immunohistochemical detection of keratins using monoclonal antibodies

The major salivary glands were examined from 69 human fetuses ranging from 10 to 40 weeks of gestation. Prenatal growth curves of developing salivary glands could be established by histological scoring, and development was divided into the early developmental stage (EDS) from 10 to 18 weeks, early intermediate developmental stage (EIDS) from 19 to 24 weeks, late intermediate developmental stage (LIDS) from 15 to 32 weeks, late developmental stage (LDS) from 33 to 40 weeks. Characteristic morphogenesis and cytodifferentiation occurred in glandular duct cells during the period of EIDS and LIDS. In the LDS, acini and ducts of the salivary glands histologically developed into a mature state similar to adult glands. Immunohistochemical staining with monoclonal antibodies (MoAbs) PKK1, KL1, K8.12, K8.13, K4.62, RPN 1160, 1162, 1163, 1164, and 1165 was performed. During the fetal period, keratin expression as revealed by MoAbs PKK1, KL1, K8.12 was well established, and the staining pattern for each of these antibodies was comparable. Other antibodies showed rare or negative staining except K8.13 which had a diffuse, non-specific staining pattern. Accordingly, the proliferation and cytodifferentiation of fetal stage keratin staining in ductal cells as revealed by MoAbs PKK1, KL1, and K8.12 showed a heterogenic distribution in both luminal and basal cells. It is a characteristic finding that the cytodifferentiation of ductal luminal cells precedes ductal basal cells. Ductal basal cells stained with MoAb K8.12 and show heterogeneity of keratin distribution continuously until the full term of gestation. The keratin staining of oral epithelium was also examined to compare with distribution of salivary gland ductal cells and oral epithelial cells. In the present study, the developmental sequence of salivary gland cells and the immunohistochemical properties of keratin proteins in these cells were described in relation to the histogenesis of salivary gland tumours.

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.

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.

Myoepithelioma--new concepts of histology and classification: a light and electron microscopic study

Based on histological, immunohistochemical, and ultrastructural studies, it is now apparent that the modified myoepithelial cell component of pleomorphic adenomas has a considerable range of cytological features. We reasoned that myoepitheliomas could be tumors with a similar spectrum of neoplastic myoepithelium but lacking the ductal element displayed in pleomorphic adenomas. A review of available salivary gland tumors identified 40 examples based on this definition. Architecturally, these myoepitheliomas displayed either nonmyxoid (solid), myxoid (pleomorphic adenoma-like), reticular (canalicularlike), or mixed growth patterns, while cytologically the lesions were composed of spindle-type (32.5%), hyaline-type (7.5%), epithelial-type (45.0%), clear-type (2.5%), or mixed-type (12.5%) tumor cells. Electron microscopy was carried out on eight examples and detailed immunohistochemistry on two methanol-fixed cases. As a result of the current review of myoepitheliomas and the description of similar lesions in the literature, it is our contention that salivary gland myoepitheliomas are not as rare as has been purported.

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.

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.