Immunohistochemical Characterization of 130 Cases of Primary Hepatic Carcinomas

Functional Histology of Salivary Gland Pleomorphic Adenoma: An Appraisal

The complex microstructure of salivary gland pleomorphic adenoma is examined in relation to function. Events related to secretion of macromolecules and absorption, responses to the altered microenvironment and controversies concerning epithelial-mesenchymal transition versus modified myoepithelial differentiation are explored. Their effects on tumor cell phenotypes and arrangements are emphasized. Heterotopic differentiation and attempts at organogenesis are also considered. The approach allows interpreting microstructure independently of histogenetic perceptions, envisaging the tumor cells as a continuum, endorsing luminal structures as the principal components, and defining pleomorphic adenoma as a benign epithelial tumour characterized by variable epithelial-mesenchymal transition, secretion/differentiation and metaplasia.

A perspective of comparative salivary and breast pathology. Part I: microstructural aspects, adaptations and cellular events

This is the first part of a review comparing the pathology of salivary and mammary glands. Here, less obvious similarities and differences in functional histology and their influences on pathology are examined with emphasis on myoepithelial cells, stromal components, analogues of mucosa-associated lymphoid tissue, steroid receptors, and intraparenchymal cells of monocytic lineage. Particular cell phenotypes (oncocytic, apocrine, neuroendocrine and clear) are critically evaluated and responses to atrophy, infarction and fine-needle aspiration biopsy procedures are highlighted together with aspects of metaplasia, regeneration, ageing and microcalcification. Areas of controversy or uncertainty which may benefit from further investigations are also discussed.

Myoepithelial cell markers in salivary gland neoplasms

We compared the immunoexpression of 5 myoepithelial cell (MEC) markers (alpha-smooth-muscle actin, calponin, h-caldesmon, vimentin, and S-100-protein) using 16 pleomorphic adenomas (PA), 15 adenoid cystic carcinomas (ACC), and 3 epithelial-myoepithelial carcinomas (EMC) of salivary glands. The alpha-smooth-muscle actin was useful for identification of MECs, especially in cribriform and tubular ACC, followed by EMC. Calponin was similar to alpha-smooth-muscle actin, except for polygonal and plasmacytoid cells of PA and for solid ACC, which showed alpha-smooth-muscle actin negative and calponin positive. H-caldesmon was negative. Vimentin immunostained all MEC types, and was negative in luminal cells. S-100 protein was expressed both in the nuclei and cytoplasm of MECs and luminal cells, especially in PA. The best way to identify MEC is using alpha-smooth-muscle actin or calponin, plus vimentin, since in tumors MECs are hardly ever fully differentiated.

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.

Immunohistochemical evaluation of the Ca(2+)-binding S-100 proteins S-100A1, S-100A2, S-100A4, S-100A6 and S-100B in salivary gland tumors

The Ca(2+)-binding S-100 proteins are involved in the regulation of a number of cellular processes and an altered expression has been reported in several neoplastic tissues. Tissue specimens of normal salivary glands (n = 23), pleomorphic adenomas (n = 60), basal cell adenomas (n = 6), canalicular ademomas (n = 2), myoepitheliomas (n = 2), adenoid cystic carcinomas (n = 26) and adenocarcinomas NOS (n = 11) were evaluated for the expression of S-100A1, S-100A2, A-100A4, S-100A6 and S-100B by using highly specific polyclonal and monoclonal antibodies generated against the recombinant human protein. In normal salivary glands, the ductal cells showed mild to intense immunoreactivity for S-100A1, S-100A2, S-100A4 and S-100A6, while S-100B was observed in nerve fibers in the connective tissue. The normal myoepithelial cells were unreactive. In pleomorphic adenoma, the luminal tumor cells of the duct-like structures showed moderate to intense immunoreactivity for S-100A2, while reactivity for S-100A1, S-100A4 and S-100A6 was relatively weak. The non-luminal cells, also termed neoplastic myoepithelial cells, showed immunoreactivity for S-100B, while tumor cells in the solid, myxoid and chondroid areas were immunoreactive for S-100A1, S-100A4, S-100A6 and S-100B. The non-luminally located tumor cells in basal cell adenomas and canalicular adenomas, and numerous tumor cells in clusters in myoepitheliomas were intensely reactive for S-100A2. In adenoid cystic carcinomas and in adenocarcinomas not otherwise specified, the luminal cells forming the tubular or cribriform structures were markedly positive for S-100A2 and/or S-100A6. Squamous metaplastic cells in salivary tumors showed intense immunoreactivity for S-100A2. The results of the present study suggest that the majority of the tumor cells in salivary neoplasms, despite the most heterogeneous tumor cell differentiation, express S-100 proteins more heterogeneously than the normal glandular ducts. The salivary ducts in normal glands, the luminal tumor cells and squamous metaplastic cells in the neoplastic lesions were intensely immunoreactive for S-100A2 as compared to S-100A1, S-100A4 or S-100A6. In contrast, the non-luminal tumor cells showed a rather heterogeneous expression of the S-100 proteins.

Salivary gland anlage tumor of the nasopharynx: a clinicopathologic and immunohistochemical study of three cases

The histologic and immunohistochemical features of three congenital pedunculated nasopharyngeal midline masses are reported. The follow-up in all cases was uneventful. The tumors were characterized by solid and cystic squamous nests and ductlike structures focally continuous with the surface squamous mucosa of the tumor. Most of epithelial structures coalesced with densely cellular stroma-like nodules. Immunoperoxidase staining showed the presence of epithelial markers in both spindle cells and epithelial structures. Spindle cells were also reactive to vimentin and smooth muscle actin, revealing their myoepithelial phenotype. Based on these observations, a diagnosis of salivary gland anlage tumor, also called congenital pleomorphic adenoma of the nasopharynx, was made. The similarity of these tumors' architecture and cellular composition to the normally developing salivary gland has led to the hypothesis of a tumorlike, hamartomatous lesion developing in a site in which minor salivary gland tissue occurs. This report reviews 12 identified cases of this tumor, of which all but one (in which the patient died of sepsis) had a favorable outcome. In an infant with respiratory distress and/or feeding difficulties, these tumors must be differentiated from other midline masses such as encephaloceles and teratomas. They appear curable by surgical exeresis only.

Demonstration of monoclonal origin of human parotid gland pleomorphic adenoma

BACKGROUND

Parotid gland pleomorphic adenoma is histologically comprised of epithelial and mesenchymal elements. It remains to be established whether this neoplasm arises from epithelial and mesenchymal elements, or solely from the epithelial element.

METHODS

In an attempt to resolve this issue, we have conducted clonal analysis on five pleomorphic adenomas. The method for clonal analysis was based on the trinucleotide repeat polymorphism of the x-chromosome-linked androgen receptor gene and on random inactivation of this gene by methylation. The epithelial and mesenchymal elements were obtained separately from the paraffin sections of the pleomorphic adenomas using a microdissection technique and then subjected to clonal analysis.

RESULTS

Clonal analysis revealed that both epithelial and mesenchymal elements were monoclonal. In addition, the same allele of the androgen receptor gene was inactivated in both elements in every case.

CONCLUSIONS

It is unlikely that the epithelial and mesenchymal elements of different origin happen to inactivate the same allele of the androgen receptor gene in all five tumors. Rather, it is more reasonable to consider that these two elements have a common single cell origin.

Polymorphous low-grade adenocarcinoma arising in the nasal cavities with an associated undifferentiated carcinoma

A case of polymorphous low-grade adenocarcinoma arising in the right nasal cavity of a male patient with previous history of kidney transplantation is reported. The tumor contained extensive areas of undifferentiated carcinoma, probably arising from the low-grade component. This combination of findings has not been previously reported in this variety of salivary gland tumor.

Myofilament localization and immunoelectron microscopic detection of muscle-specific actin in neoplastic myoepithelial cells in pleomorphic adenomas and myoepitheliomas

Elucidating the cellular characteristics of the nonluminal or myoepithelial cells of pleomorphic adenomas is one approach to establishing the diagnostic criteria for myoepitheliomas. Ultrastructural features of nonluminal tumor cells in 22 pleomorphic adenomas and of tumor cells in 9 myoepitheliomas were assessed from micrographs of routinely fixed and epoxy resin-embedded samples. Recognizable myofilaments were only moderately prominent in 1 myoepithelioma. In the rest of the cases, irrespective of whether nonluminal cells of pleomorphic adenomas or tumor cells of myoepitheliomas were spindle, angular, round, or plasmacytoid in form, myofilaments were noted only in one third of the cases and were present even in these in a small proportion of the tumor cells. Intermediate filament accumulations and basal lamina were more frequent findings associated with nonluminal tumor cells. Six pleomorphic adenomas and 2 myoepitheliomas had been fixed in half-strength glutaraldehyde and embedded in LR White resin for immunoelectron microscopic detection of muscle-specific actin. In 3 (2 pleomorphic adenomas and myoepitheliomas) of these 8 cases, readily visualized bands of filaments in many tumor cells were strongly labeled by the colloidal gold probe detecting muscle-specific actin even when myofilaments were minimal and infrequent in 2 cases and undetectable in the third by routine transmission electron microscopy. Lack of myofilament detection by immunocytochemistry or routine electron microscopy does not exclude a diagnosis of pleomorphic adenoma or myoepithelioma when growth patterns and cytology indicate such diagnoses. Immunoelectron microscopy, in fact, shows that muscle-specific actin can be detected even when myofilaments or muscle actin are apparently absent or minimal by routine electron microscopy or immunohistochemistry, respectively. Because examples of pleomorphic adenoma and myoepithelioma each with similar histologic and cytologic features of the myoepitheliomatous cells can have variable degrees or complete absence of expression of myofilaments or muscle-specific actin, the time-honored term myoepithelial for the nonluminal cells of pleomorphic adenomas and the term myoepithelioma are legitimate even in the absence of those markers that are specific for normal myoepithelial cells.

Immunolocalization of alpha 2, alpha 5, and alpha 6 integrin subunits in salivary tissue and adenomas of the parotid gland

The localization of the integrin subunits alpha 2, alpha 5, alpha 6 was studied immunohistochemically in samples of normal salivary gland and in a series of 8 pleomorphic adenomas, 5 Warthin's tumors, and 2 basal cell adenomas. In normal salivary tissue, acinar and ductal cells expressed alpha 2 and alpha 6 chains at the basal cell pole facing the basement membrane. alpha 2 also localized at sites of cell-cell contact. No staining of the epithelial component was seen with alpha 5. The polarized expression of alpha 2 and alpha 6 subunits was retained in salivary adenomas. These subunits were present at the basal cell pole of solid nests, tubules and ducts of pleomorphic adenomas, as well as of the basal layer of the epithelium of Warthin's tumor, and of the trabecular structures of basal cell adenomas. The alpha 5 subunit was consistently expressed only by cells embedded in the myxoid or chondroid matrix of pleomorphic adenomas. We conclude that the pattern of a integrin subunit expression in salivary adenomas may be related to the "epithelial" or "mesenchymal" phenotype of the neoplastic cells.

Intermediate filament reactivity in hyperplastic and neoplastic lesions from medaka (Oryzias latipes)

To determine if hyperplastic and neoplastic lesions from medaka showed similar immunoreactivity to intermediate filament antibodies as the tissues of origin, two week old medaka were exposed to 10 or 20 mg/L of methylazoxymethanol acetate for two hours and transferred to clean water for up to six months. Using a streptavidin peroxidase method, paraffin embedded Bouins fixed neoplasms were incubated with cytokeratin, vimentin, or neurofilament antibodies. Like their nonneoplastic cellular counterparts, hepatocellular carcinoma, pancreatic acinar carcinoma and mesenchymal neoplasms including hemangioma and hemangiopericytoma reacted negatively to cytokeratin antibodies. Cholangiocarcinoma, mesothelioma, and proliferative lesions containing biliary epithelial cells reacted positively to cytokeratin antibodies. All neoplasms and proliferative lesions were negative with vimentin and neurofilament antibodies. These data indicate that while some epithelial neoplasms showed cytokeratin reactivity similar to the parent tissues, additional markers are needed to identify mesenchymal tissues and neoplasms.

Pathology of the salivary glands: the contribution of electron microscopy

Electron microscopy has a limited role in the diagnosis of primary salivary gland tumors, although it can be helpful in metastatic lesions of possible salivary gland origin. The diversity of subtypes in salivary gland tumors, as well as the range of histomorphology within any one subtype, is unparalleled in any other human tumor. This and their relative infrequency causes diagnostic problems for pathologists. Ultrastructural techniques have been of major importance in determining the inter-relationship of these tumors for classification purposes, revealing the subtle variations in common cellular differentiation pathways, determining the organization of tumor cells, and displaying the importance of extracellular matrix materials in establishing diagnostic criteria for each of the many subtypes. Electron microscopy has also been valuable in non-neoplastic salivary gland disease and has an increasing role in experimental studies involving tissue from human and animal salivary parenchyma.

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.

Histopathology of myoepithelial (basocellular) hyperplasias in adenosis and epitheliosis of the breast demonstrated by the reactivity of cytokeratins and S100 protein. An analysis of heterogenic cell proliferations in 90 cases of benign and malignant breast diseases

This study on the different types of epithelial hyperplasia in fibrocystic disease was inspired by the observation of myoepithelial (basocellular) hyperplasia identified by strong expression of S100 protein and a weak reaction with antibodies against cytokeratin (KL1) in cells forming solid and acinar buds. The cells do not contain immunohistochemically detectable actin or desmin. Glandular transformation and proliferation give rise to basocellular circumductal adenosis. Normal breast tissue, 51 cases of fibrocystic disease with mild, florid and atypical hyperplasias, 7 fibroadenomas and 20 cases of carcinoma in situ were studied and a semiquantitative analysis revealed basal buds and adenosis in less than 40% of cases of mild hyperplasia and up to 73% in florid hyperplasia. Epitheliosis is characterized by a heterogeneous cell pattern with cells positive for S100 protein in 30-60%, but in small ducts up to 100% with an immediate connection to the basal cell layer were positive. Carcinoma in situ contained very rare tumour cells positive for S100 protein. The cells expressing S100 protein in terminal ducts, in adenosis and epitheliosis showed only some of the characteristics of myoepithelial cells, since they lack immunoreactivity with antibodies against actin. These basal clear cells are interpreted as transitional or indeterminate cells with features of myoepithelial precursor cells, but with the ability to develop basocellular nodular and glandular hyperplasia in the ductulo-lobular units in cases of adenosis and juvenile fibroadenoma.

Immunogold localization of actin and cytokeratin filaments in myoepithelium of human parotid salivary gland

Myoepithelial cells of salivary gland are uniquely specialized cells; their function is unclear, but the considerable complement of muscle-specific actin suggests contractility is one function. By routine transmission electron microscopy myofilament visualization is variable. Some myoepithelial cells appear to have limited and only focal aggregates of myofilaments, while others seem to have readily appreciated myofilaments within a longitudinally oriented cytoplasmic zone at the basal portion of the cell. However, immunogold electron microscopy using the anti-muscle-specific actin antibody, HHF35, while indicating a basal distribution for the muscle-isoform of actin in a platelike fashion in certain myoepithelial cells, also reveals that others associated with both intercalated ducts and acini have a more generalized distribution of myofilaments throughout the cytoplasm. Actin was also noted within tonofilaments and double immunogold labeling using both the HHF35 and AE1/AE3 (anticytokeratins) antibodies confirmed the variable interrelationship of these two filaments. Within any one myoepithelial cell, actin and cytokeratins might colocalize in some areas of the cytoplasm containing filaments, but not in adjacent zones. These results suggest that intermediate filaments and myofilaments are complexly organized in myoepithelial cells, and that quantitative and qualitative differences exist in the expression and distribution of intermediate filaments and myofilaments. These cells are likely structurally, if not functionally, heterogeneous.

Characterization of a novel cell line from pleomorphic adenoma of the parotid gland with myoepithelial phenotype and producing interleukin-6 as an autocrine growth factor

A cell line was obtained from a primary culture of a pleomorphic adenoma of the parotid gland in a 24-year-old woman. The cells of the line (PA 16/23) grew spontaneously in minimal culture conditions and showed stable morphologic characteristics over 30 passages. PA 16/23 cells had immunophenotypic and ultrastructural features similar to those of transformed myoepithelial cells, which are regarded as the precursors of pleomorphic adenomas. Furthermore, these cells have been demonstrated immunocytochemically to contain interleukin-6 (IL-6) on light and electron microscopic examination. IL-6 also has been found by enzyme-linked immunosorbent assay in the culture supernatant and has been proven to be capable of stimulating growth of the PA 16/23 cells.

Myoepithelial differentiation in benign sweat gland tumors. Demonstrated by a monoclonal antibody to alpha-smooth muscle actin

One hundred and two cases of benign sweat gland tumors of the skin were studied for the presence of myoepithelial cells specifically identified by a monoclonal antibody to alpha-smooth muscle actin on paraffin-embedded tissues. The monoclonal antibody gave a positive result in 12 of 12 cases of cylindroma, 14 of 16 cases of spiradenoma, 2 of 2 cases of apocrine tubular adenoma (papillary eccrine adenoma), 5 of 5 cases of apocrine hidrocystoma, 5 of 5 cases of hidradenoma papilliferum, and in 10 of 10 cases of syringocystadenoma papilliferum. Rare myoepithelial cells were detected in only 1 of 10 cases of mixed tumor, apocrine type. There was no immunoreactivity for alpha-smooth muscle actin in eccrine hidrocystoma (2 cases), mixed tumor of eccrine type (2 cases), syringoma (7 cases), hidroacanthoma simplex (1 case), eccrine poroma (14 cases), clear cell hidradenoma (15 cases), and in 1 case of eccrine syringofibroadenoma. Our data support the concept that myoepithelial cells are seen in most sweat gland tumors considered to differentiate toward the secretory coil of the normal sweat gland. In contrast, myoepithelial cells are absent in tumors showing differentiation toward the excretory (ductal) component of the gland.

Immunohistochemical and ultrastructural correlates of muscle-actin expression in pleomorphic adenomas and myoepitheliomas based on comparison of formalin and methanol fixation

The degree and range of differentiation of the cells referred to as myoepithelial-like in pleomorphic adenomas and the tumour cells of myoepitheliomas are not definitely established. This type of information is critical for establishing reliable diagnostic criteria, such as expression of muscle-specific actin and ultrastructural identification of myofilaments, in these and other salivary gland tumours. Pleomorphic adenomas (18) and myoepitheliomas (5), of which 10 cases were fixed only in formalin and 13 cases where tissues were fixed in both formalin and methanol/acetic acid, were studied. Each tumour and normal accompanying parotid was immunostained with two monoclonal antibodies for smooth muscle actin, HHF35 and MSA. Staining of myoepithelial cells was absent in certain samples of normal gland with both HHF35 (15%) and MSA (69%) when formalin-fixed tissue was used. Using formalin-fixed tissue from 15 pleomorphic adenomas/myoepitheliomas, 2 (14%) had focal positivity with HHF35, while 8 cases (57%) were positive with MSA. However, a certain degree of false positivity was suspected since in samples of normal parotid, both acinar and duct cells were frequently stained, particularly with MSA. With methanol/acetic acid-fixed tissue only 4 of 13 cases (31%) were positive with either MSA or HHF35 and 2 of these only had a minor proportion of the tumour cells expressing muscle-specific actin. Using alcohol-fixed tissue, myoepithelial cells were strongly stained in all examples of normal parotid gland with both anti-actin antibodies. In 5 cases examined by electron microscopy, there was no apparent correlation between immunohistochemical results and the presence or absence of cytoplasmic filament accumulation. The results indicate considerable tumour cell heterogeneity in muscle-specific actin expression and suggest that non-luminal cells in pleomorphic adenomas and the tumour cells in myoepitheliomas may differentiate as classical myoepithelial cells, as partially differentiated (i.e. modified myoepithelial cells) or as the counterpart of basal cells present in the intra- and interlobular ducts of normal salivary gland.

Malignant myoepithelioma of the larynx with massive metastatic spread to the liver: an ultrastructural and immunocytochemical study

A malignant myoepithelioma arising in the submucosal glands of the larynx of a 71-year-old man is reported. The patient presented with a neck mass and massive metastatic involvement of the liver. Light microscopy of a liver biopsy specimen and fine-needle aspiration sample of the neck mass revealed a poorly differentiated carcinoma. Electron microscopic study of a second liver biopsy specimen demonstrated unequivocal features of myoepithelial differentiation; this was further confirmed by the strong cytokeratin and S-100 protein positivity and carcinoembryonic antigen negativity of the tumor cells. Myoepitheliomas are rare tumors, and most reported cases have been benign or of low-grade malignancy. The present case is unique because of its mode of presentation and fulminant course. It also underscores the usefulness of electron microscopy as a diagnostic modality in the work-up of metastatic lesions.

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.

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.

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.

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.

Immunohistochemical characterization of epithelial cells in human lacrimal glands. II. Inflammatory and neoplastic lesions of lacrimal glands

The distribution of cytokeratins (CK), actin, lactoferrin (Lf), lysozyme (Ly), vimentin and S-100 protein was immunohistochemically investigated in paraffin-embedded specimens of five inflammatory and five neoplastic lesions of lacrimal glands (LGs). Atrophic acini in dacryoadenitis reacted with antibodies (ABs) KL1 and Pkk1 (CK 7, 8, 17, 18) in a manner similar to ducts. Apart from myoepithelial cells and some luminal-duct cells, the remaining epithelia in dacryoadenitis were negative with AB 34 beta E12 (CK 5). The number of AB HHF35 (actin)-positive myoepithelial cells was not altered in dacryoadenitis. Epithelia in dacryoadenitis reacted weakly but consistently with Lf while revealing weak and inconsistent staining for Ly. Vimentin was negative in epithelial cells in dacryoadenitis except in one case. S-100 protein was detected only in epithelia of inflammatory major LGs. Epimyoepithelial islands in lymphoepithelial proliferation reacted variably for CKs, Lf, Ly and vimentin and remained negative for actin and S-100. In pleomorphic adenomas, neoplastic cells showing duct-like differentiation (luminal) reacted consistently with CK 7, 8, 17, 18 and S-100 protein and inconsistently with CK 5, Lf and Ly but remained negative for actin and vimentin. Other neoplastic cells (ovoid/peripheral cells) stained consistently for CK 5, vimentin and S-100 protein and focally for CK 7, 8, 17, 18, actin, Lf and Ly. Spindle-form neoplastic cells found in the stroma exhibited vimentin and S-100 protein and, less frequently, actin. Determination of these antigens in pleomorphic LG adenomas may help to evaluate their prognosis.

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.

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.

Immunohistochemical demonstration of lysozyme and lactoferrin in salivary pleomorphic adenomas

Immunohistochemical identification of lysozyme and lactoferrin was made in salivary pleomorphic adenomas (147 cases) and the staining patterns were evaluated with respect to the histological features and histogenesis. In normal salivary glands, the intercalated duct cells gave positive staining for lysozyme in major glands, and serous acinar cells, demilune cells, and interlobular duct cells were positive in minor glands. Lactoferrin staining was irregularly positive in serous cells and ductal epithelium. In pleomorphic adenomas, the reaction for lysozyme was positive in 14% (21/147) of the cases, and was confined to luminal cells of tubulo-ductal structures. Lactoferrin in pleomorphic adenomas was distributed in luminal tumor cells (51%; 75/147), in outer tumor cells (3%; 4/147), and in both luminal and outer tumor cells (5%; 7/147) in tubulo-ductal structures; it was also detected in plasmacytoid myoepithelial cells (5%, 8/147). However, modified myoepithelial cells and other types of neoplastic myoepithelial participants were negative for lactoferrin staining. The occurrence of both lysozyme and lactoferrin in salivary pleomorphic adenomas suggests their participation in the local defense mechanism in the tumor.

Multiple expression of tissue markers in mucoepidermoid carcinomas and acinic cell carcinomas of the salivary glands

The distribution of various tissue antigens was studied in mucoepidermoid carcinomas (n = 74) and acinic cell carcinomas (n = 38) by means of immunocytochemistry. Mucoepidermoid carcinomas were generally positive for cytokeratin and showed double expression for cytokeratin and vimentin in 31.1% and triple expression for cytokeratin, vimentin and GFAP in 24.1%. CEA was studied using new monoclonal antibodies which distinguish between epitopes that are present on CEA alone and those which are present on nonspecific cross reacting antigens as well. The monospecific CEA antibody was completely negative in mucoepidermoid carcinomas, while nonspecific cross reacting antigens (NCAs) were positive in mucoepidermoid carcinomas to a varying degree. Alpha 1-antichymotrypsin, a marker formerly thought to be specific for tissues for histiocytic origin, was positive in 85.1% of mucoepidermoid carcinomas. Twenty three percent of mucoepidermoid carcinomas showed focal infiltration by S-100 positive dendritic stromal cells, tumour cell being negative. Leu-M1 antigen was positive in 58.1% of mucoepidermoid carcinomas. Acinic cell carcinomas were generally positive for cytokeratin and in single cases showed double expression for cytokeratin and vimentin and triple expression for cytokeratin, vimentin and GFAP. Monospecific CEA antibody positivity could be demonstrated in 24.2% of acinic cell carcinoma, while nonspecific cross reacting antigens (NCAs) were positive in acinic cell carcinomas to a varying degree. Alpha 1-antichymotrypsin was positive in 97.4% of acinic cell carcinomas. 2.5% of acinic cell carcinomas showed focal infiltration by S-100 positive dendritic stromal cells, 2.5% of acinic cell carcinomas were positive for S-100 protein with no dendritic stromal cells present. Leu-M1 antigen was positive in 86.8% of acinic cell carcinomas. For S-100 protein and Leu-M1, no correlation with the clinical course, as reported previously for other tumours, could be observed.

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 localization of the alpha and beta subunits of S-100 protein in pleomorphic adenoma of the salivary glands

The immunohistochemical expression of the alpha and beta subunits of S-100 protein in reactive, modified and transformed of myoepithelial cells, salivary pleomorphic was investigated using monoclonal antibodies. With S-100 alpha, normal salivary glands showed strong staining in serous acinar cells and moderate to slight staining in ductal segments, and with S-100 beta staining was slight or negative in acinar cells, but strong in nerve fibres. In pleomorphic salivary adenomas, the immunohistochemical distribution of S-100 alpha and beta proteins indicated great variation in the tumour cells. Some neoplastic cells gave similar staining for both S-100 alpha and beta, others were strongly positive for S-100 alpha and stained only slightly for S-100 beta, or vice versa. Yet other cells were positive for S-100 alpha and negative for S-100 beta, or vice versa. Pleomorphic salivary adenomas were classified both by histopathological criteria and by their staining pattern for S-100 alpha and beta proteins. Great heterogeneity in S-100 alpha and beta protein expression was found in individual tumour cells of both ductal and myoepithelial origin, and no regular pattern was identified. The cellular origin of salivary pleomorphic adenomas is discussed in terms of S-100 alpha and beta protein immunohistochemistry. Pleomorphic adenoma cells may be transformed from reserve cells into tumour cells displaying biologic properties of myoepithelial cells, ductal cells, or a mixture of both.

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.

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.

Immunohistochemical localization by monoclonal antibodies of S-100 alpha and beta proteins in mixed tumours and adenomas of the skin

A study using monoclonal antibodies was made to evaluate the immunohistochemical localization of S-100 protein subunits alpha and beta in a total of 41 mixed tumours and adenomas of sweat gland origin. Normal eccrine glands showed positive staining for S-100 alpha in the secretory portion and in epithelial cells located in the transitional area from the coiled duct to the intraepidermal duct, as well as granular deposition of S-100 beta at the luminal surface of the secretory coil and duct. The myoepithelial cells were negative for S-100 alpha and beta. In mixed tumours, the tumour cells were round or oval in shape and displayed markedly positive staining for S-100 alpha and slightly positive or negative staining for S-100 beta. S-100 alpha staining in clear cell tumours was typically more intense than in any other sweat gland tumour. It is possible that clear cell tumours may arise from the transitional area of sweat glands. Spindle cell tumours displayed on abundance of S-100 alpha subunits but little S-100 beta. Occasional spindle cells located in the outer layer of tubular structures within tumours gave positive S-100 alpha staining. This result was different from that seen in pleomorphic salivary adenomas. Cells having undergone chondroidal changes revealed a positive S-100 reaction.