[Crystalloids in salivary gland pleomorphic adenoma]

We examined crystalloids in salivary gland pleomorphic adenomas. The crystalloids were detected in 4 of 34 pleomorphic adenomas (11.7%). In three cases they were found in the minor salivary gland and in one case in the major salivary gland. Light microscopy revealed that all the crystalloids were in parenchyma. They were composed of eosinphilic structure and radially arranged clusters of needle-shape fibers. The central parts sometimes contained clear space. They were usually closely surrounded by neoplastic myoepithelial cells. All 4 cases containing crystalloids were million reaction-negative and positive to van Gieson, Mallory and Reticulin Silver Impregnation stains. Therefore all the crystalloids in our 4 cases were considered as collagen-rich.

[An immunoelectron microscopic study of the myoepithelial cells in salivary gland pleomorphic adenoma]

In the present study, the neoplastic myoepithelial cells in five pleomorphic adenomas of parotid gland were labeled with actin, myosin, S-100 protein, glial fibrillary acidic protein (GFAP) and vimentin. We have found that the neoplastic myoepithelial cells have many different morphologic features, they are the principal proliferating cells in the tumors. In the myxoid region, part of the neoplastic myoepithelial cells have early chondroid differentiation, this shows that the neoplastic myoepithelial cells take the important role in the histogenesis of the tumors.

Unique chromosomal rearrangement and mucin production in a novel salivary myoepithelial cell strain

Pleomorphic adenoma is the most frequently occurring benign neoplasm of the salivary glands. We describe the culture characteristics, biochemical properties, immunohistochemical staining, and genetic rearrangements found in a novel cell strain (UNC4) established from a human benign pleomorphic adenoma. Serum and/or butyrate stimulation of UNC4 cultures results in upregulation of mucin production. This is confirmed by periodic acid-Schiff, periodic acid-Schiff digest, alcian blue, and mucicarmine staining as well as by gel electrophoresis. Fluorescent immunohistochemical studies detect cellular cytokeratin, desmin, and epithelial membrane antigen. Immunofluorescent staining for S100 protein is negative. Examination of the karyotype of UNC4 reveals a unique rearrangement between one chromosome 8 and the two chromosome 9s involving the 8q12 locus. UNC4 represents an in vitro model of a benign salivary gland neoplasm that can provide the basis for further molecular and biochemical studies on genetic rearrangement and salivary mucin production.

Argyrophilia in nucleolar organizer regions (AgNOR) in adenoid cystic carcinoma and polymorphous low-grade adenocarcinoma of the salivary glands

Nine cases of adenoid cystic carcinomas (ACC) and three cases of polymorphous low-grade adenocarcinomas (PLGA) of the salivary glands from the Surgical Oral Pathology Service of the University of São Paulo School of Dentistry were examined by means of the silver-staining nucleolar organizer regions (AgNOR) technique. Quantitative and dimensional analyses of NORs were carried out. Our findings suggest that solid and cribriform patterns of ACC have a higher cellular activity than that presented by tubular ACC and PLGA.

[The matrical fibrous structure in pleomorphic adenoma of the parotid gland--three dimensional visualization by the freeze-fracture deep-etch replica method]

Three dimensional visualization of the matrical fibrous structure of pleomorphic adenomas of the parotid glands was performed by the freeze-fracture, deep-etch replica method(D-E). Three types of fine architecture, two in the myxoid area and one in the chondroid area, which could not be observed by ordinary transmission electron microscopy (TEM), were revealed. In addition, granular connections between the tumor cell membrane and matrical fibers, probably cell surface proteins, were visualized. In the myxoid area, one type of matrix which has a structure that cannot be identified on TEM, D-E demonstrated a uniform fine fibrous network consisting mainly of 7-10 nm diameter filaments and various architectures. These structural components were interlinked in a specific order and formed a basement membrane-like structure which contained the so-called 'hexagon-lattice structure' reported by Sawada. Another type which appears as an irregular spotty structure and a few collagen-bundles on TEM, was revealed by D-E to be composed of a fine fibrous network and collagen-bundles. The collagen-bundles and the network were also interconnected to form a more complicated network. In the chondroid area, the type of matrix appearing as a mottled amorphous area consisting of electron-dense and electron-lucent parts on TEM, was shown by D-E to be composed of mainly collagen-bundles and a less prominent fine fibrous network. As for the cell surface, there were numerous granular structures which were seen to be anchored within the membrane and rigidly connected with 7-10 nm diameter fibrils. However, direct connections between the cell membrane and collagen-bundles were unremarkable. No tumor cell basement membrane was observed. These findings indicate that, in constructing the tumor tissue and maintaining the tumor cells, the matrix could preserve suitable environment for these cells, and that the matrix and tumor cells may influence each other. To date, the matrix of this tumor has been regarded as a relatively uninteresting element. It was thought to lack any apparent structure and have little involvement in tumor biology. We, on the other hand, believe that this tumor matrix is an important component, and that future investigation of this matrix will provide new insights into the study of pleomorphic adenoma.

Rare expression of the c-erbB-2 oncoprotein in salivary gland tumors: an immunohistochemical study

An immunohistochemical study of c-erbB-2 oncoprotein expression was carried out on 201 cases of primary salivary gland tumors, using a polyclonal antibody, raised to the intracytoplasmic domain of the c-erbB-2 oncogene product. An intense membrane reactivity was observed in one case of sialocarcinoma transformed from pleomorphic adenoma (n = 8) and one case of mucoepidermoid carcinoma (n = 22). A comparative histopathologic evaluation of c-erbB-2 positive tumors showed marked variation in cell size, nuclear pleomorphism, multinucleation, a high mitotic rate and increased lymphoid cell infiltration and an aggressive clinical course with poor survival. The results indicate that c-erbB-2 oncoprotein is rarely expressed in malignant salivary gland tumors. However, the overexpression appears to have a distinct histopathologic feature, but a larger study incorporating histopathology and clinical data would be necessary to correlate the significance of c-erbB-2 oncogene product in salivary malignant tumors.

Nucleolar organizer regions in malignant salivary gland tumors

Proliferative activity of carcinomas arising from salivary glands was analyzed by enumeration of argyrophilic nucleolar organizer regions (AgNORs). The mean numbers of AgNORs in the various tumors were as follows: mucoepidermoid carcinoma, 2.20; acinic cell carcinoma, 2.51; adenoid cystic carcinoma (ACC), 2.57; carcinoma in pleomorphic adenoma, 1.00 (benign component) and 3.99 (cancer-bearing area); salivary duct carcinoma, 4.49; polymorphous low-grade adenocarcinoma, 3.37; sebaceous carcinoma, 2.57; oncocytic carcinoma, 4.63; adenocarcinoma, 4.53. Cells of most tumors showed heterogeneous activity within the same tumor. In mucoepidermoid carcinoma, the mucous cells had suppressed activity in comparison with the epidermoid cells and intermediate cells. In ACC, the activity of the tumor cells increased according to growth pattern in the order tubular, glandular and solid. In carcinoma in pleomorphic adenoma, vigorous proliferative activity was observed in the malignant component, whereas less active cells were seen in the myxoid or chondroid matrix. AgNOR staining was useful for distinguishing benign from malignant regions in carcinoma in pleomorphic adenoma. Our results suggest that mucoepidermoid carcinoma, acinic cell carcinoma and ACC, except for that with a solid growth pattern, may be considered as low-grade malignancies, whereas solid-type ACC, the cancer component in carcinoma in pleomorphic adenoma and some of the other carcinomas have high-grade malignant behavior.

Proliferative activity in normal salivary gland and pleomorphic adenoma. A study by argyrophilic nucleolar organizer region (AgNOR) staining

Proliferative activity of the structural components of normal salivary glands (27 cases) and characteristic histological areas in salivary pleomorphic adenoma (51 cases) was examined by visualization of argyrophilic nucleolar organizer regions (AgNORs). In the normal salivary gland, there were clusters of cells, each with two or three AgNOR dots, within the intercalated ducts. The mean number of AgNORs in this portion was 1.80, which was significantly higher than in the other epithelial parts. This indicates vigorous proliferative activity of the intercalated ducts, and thus the ducts may play an important role as reserve cells in neoplastic transformation. In pleomorphic adenoma, solid nests had a high AgNOR count (1.61), showing a significant difference from the tumor cells scattered in the "stroma". Thus the decrease in proliferative ability might occur concurrently with formation of the extracellular matrix.

Polyploidy in pleomorphic adenomas with cytological atypia

Occasionally, in fine-needle aspirates of pleomorphic salivary gland adenomas, considerable cytonuclear atypia is present, which may give rise to a false-positive diagnosis. In this study DNA cytophotometry was performed on Feulgen restained smears prepared from material obtained by needle aspirates of normal salivary glands (n = 4), pleomorphic adenomas with (n = 5) and without (n = 4) atypia and a carcinoma in a pleomorphic adenoma. The results showed a clear diploid DNA histogram in the specimens of normal salivary gland and pleomorphic adenomas without atypia. In contrast, in the pleomorphic adenomas with atypia a distinct polyploid pattern was present in three out of the five DNA histograms with DNA values in 2c, 4c and 8c ranges. In two of these cases a 16c peak was also present and in the two remaining cases tetraploidy was demonstrated. In the carcinoma a main stemline at 4c was found. This report once more emphasizes the possible atypia which may be present in FNA of pleomorphic adenomas of the salivary gland. The atypia is due to polyploidy in a histologically benign tumour.

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.

Nuclear ultrastructure of human parotid gland tumors with special focus on nuclear bodies

The purpose of our study was to determine the morphology and the proportion of NB in 20 human parotid gland tumors. Types I and III NB were observed in benign as well as malignant tumors. Some atypical forms ("onion-like" NB and NB with lipidic inclusions) were found in benign tumors. The proportion of nuclear profiles containing one and more NB varied from 0 to 60% in the benign tumors, and from 4 to 50% in the malignant tumors. Nuclei containing 3 and more NB were observed as well in the benign as in the malignant tumors. The NB ratio cannot be taken for a malignancy criteria.

Immunohistochemical demonstration of type II collagen in the chondroid tissue of pleomorphic adenomas of the salivary glands

A study was done to investigate the presence of type II collagen and elastin in the metaplastic chondroid tissue of 21 pleomorphic adenomas of the major and minor salivary glands. Type II collagen was detected with anti-bovine type II collagen antibody after double digestion of histological sections with trypsin and hyaluronidase. The immunoreaction was positive in the chondrocytic cells and intercellular matrix. Elastic fibers in the chondroid tissue were found by orcein staining; they were scarce and randomly distributed. Although the presence of type II collagen and elastin in the metaplastic chondroid tissue is not directly implicated in the genesis of the tumor, it reveals a unique and high grade of cellular differentiation in comparison with true cartilage.

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.

Coexpression of intermediate-sized filaments in sialadenoma papilliferum and other salivary gland neoplasms

The neoplastic cells present in a sialadenoma pappiliferum were found by immunoperoxidase method and immunofluorescent staining technique to co-express 3 different types of intermediate-sized filaments (IFs) defined by monoclonal antibodies to cytokeratin, vimentin and desmin. When other salivary gland tumors such as 18 pleomorphic adenomas, 15 adenolymphomas, 2 oxyphilic adenomas, 7 mucoepidermoid tumors, 5 acinic cell tumors, 8 adenoid cystic carcinomas and 6 adenocarcinomas were examined immunohistochemically for the expression of IFs, no tumors with all 3 types of IFs observed in sialadenoma papilliferum were found.

Ultrastructural and immunohistochemical observations of a true malignant mixed tumor (carcinosarcoma) of the tongue

True malignant mixed tumor (TMMT) of salivary glands, with both carcinomatous and sarcomatous components, is exceedingly rare. We offer a case of TMMT in a 79-yr-old man, which may represent the first report example of this unusual neoplasm arising in the tongue. The carcinomatous component was mainly of solid basaloid carcinoma with focal glandular differentiation, while the sarcomatous component was composed of pleomorphic elements such as chondrosarcoma, myxosarcoma and fibrosarcoma. Carcinoma cells at the periphery of solid nests occasionally merged into these sarcomatous elements. Immunohistochemically, basaloid carcinoma cells showed positive reaction for both low molecular weight cytokeratin and S-100 protein, whereas carcinoma cells lining ductal spaces were positive for a wide spectrum of keratin and EMA. The sarcomatous elements revealed the presence of vimentin and S-100 protein. Ultrastructurally, basal lamina-like material and/or mucoid precipitates often accumulated separating the tumor cells from each other singly or into a few cell group. Some sarcomatous cells assumed the myoepithelial features, such as the presence of microfilament bundles with dense bodies and pinocytotic vesicles along the cell periphery. These findings may indicate that TMMT shares a common histogenesis with pleomorphic adenoma.

Nucleolar organizing regions (NORs) in pleomorphic adenomas of the salivary glands

The number of nucleolar organizing regions (NORs) can be used to reveal the degree of cell activity or metabolism in histopathology specimens. Forty-one cases of pleomorphic adenomas of the salivary glands were studied with a silver nitrate colloid staining method to demonstrate the NORs in the cells of the solid and duct pattern areas and in chondroid areas. Acinic and intercalated ducts cells of the surrounding normal salivary glands were also examined. The data was analyzed statistically and it was found that the cells in the solid/ductal areas had a higher cellular activity than the chondroid cells. This difference is probably directly related with the possibility of malignant transformation and the incidence of the different types of malignant pleomorphic adenomas. Furthermore, it is concluded that the number of NORs in pleomorphic adenomas to define malignancy should be done discriminating between the different histologic patterns because of their different metabolic activities.

[Ultrastructural and histochemical study of a pleomorphic adenoma of the palate]

Histochemical and ultrastructural study of the epithelial regions forming lumina in one case of pleomorphic adenoma of the palate was undertaken. The ultrastructural findings suggest that these epithelial regions are derived from the intercalated ducts. The presence in the cytoplasm of periluminal cells of pinocytotic vesicles and vacuoles containing material similar in appearance of that seen in the luminal supports a reabsorptive activity of these cells. The microcalculi of calcium phosphate occasionally seen in the cytoplasm of these cells may be formed by the phagocytosis of the endocytotic material from the lumina.

Pleomorphic adenoma (benign mixed tumor) of the breast. An immunohistochemical, flow cytometric, and ultrastructural study and review of the literature

Pleomorphic adenoma (or benign mixed tumor) of the breast is a rare benign neoplasm that might be misinterpreted both clinically and pathologically as a malignant tumor. The authors present an additional case of this unusual lesion studied by immunohistochemistry, electron microscopy, and flow cytometry. A 77-year-old white woman presented with a 2-cm, nontender, mobile, calcified, right subareolar mass suggestive of a fibroadenoma. Microscopically, the tumor resembled a pleomorphic adenoma occurring in salivary glands. Positive immunostaining for S-100 protein, cytokeratin, and muscle-specific actin, as well as the ultrastructural presence of intermediate filaments with dense bodies and intercellular junctions, supported the predominant myoepithelial cell differentiation within the tumor, whereas the epithelial cell component stained only with cytokeratin and contained formed lumina with surface microvilli. The DNA pattern was diploid. The patient is alive and well 14 months after surgery. The authors' findings confirm that pleomorphic adenoma of the breast is a benign neoplasm in which myoepithelial cell proliferation plays a major role in tumorigenesis.

Immunolocalization of basement membrane molecules in the stroma of salivary gland pleomorphic adenoma

In order to determine the participation of basement membrane molecules in formation of its characteristic stroma, 30 cases of salivary gland pleomorphic adenoma were examined by immunohistochemical staining for type IV collagen, laminin, heparan sulfate proteoglycan, and entactin. The stroma was histopathologically classified into four types: hyaline, fibrous, myxoid, and chondroid. Immunohistochemically, type IV collagen and laminin were more intensively localized in hyaline, fibrous and chondroid types of stroma, whereas heparan sulfate proteoglycan was more prominent in myxoid areas. The results suggest that the stroma contains these basement membrane components, which are possibly biosynthesized by epithelial tumor cells, and that histological variety of the stroma depends on proportion of local contents of each basement membrane molecule.

Light microscopic, ultrastructural and immunocytochemical spectrum of malignant lacrimal and salivary gland tumors, including malignant mixed tumors

Ten malignant myoepithelial tumors of the salivary glands and one of lacrimal gland origin were studied by light, electron microscopy and immunocytochemistry. The light microscopic appearance of the tumors varied from primarily spindle cell neoplasms (two cases), to others with predominantly epithelial components (four cases) and mixed varieties (five cases). Therefore, they can be confused with other epithelial and mesenchymal neoplasms. The electron microscopic spectrum varied from tumors with widespread and typical myoepithelial differentiation (i.e. myofilament bundles at the cell periphery, attachment plaques and intercellular junctions) to some with diffusely distributed filaments, without associated spindle densities but with attachment plaques, and others with evidence of duct formation and containing scattered cells showing intracytoplasmic tonofilaments. Often the tumors revealed mixed ultrastructural features; the relative numbers of the different cellular components was variable. The eleven neoplasms were S-100 protein, actin and keratin positive, either focally or diffusely, with varying degrees of intensity. Ten of the eleven tumors were positive for vimentin and nine of ten tested expressed carcinoembryonic antigen. Only two of nine were focally positive for glial fibrillary acidic protein. The study emphasizes the variable light microscopic appearances of these neoplasms and their immunocytochemical and ultrastructural spectrum. Accurate determination of myoepithelial differentiation sometimes requires careful evaluation of the light, ultrastructural and immunocytochemical findings. If all three diagnostic modalities are not utilized, it is likely that some of these neoplasms will be improperly classified.

Crystalloids in salivary gland pleomorphic adenomas

Two types of crystalloids in salivary gland pleomorphic adenomas were studied by light microscopy and electron microscopy. The first type of crystalloid, the previously described tyrosine-rich crystalloid, was identified in three (1.5%) of 205 cases. The crystalloids by light microscopy assumed a radial configuration, resulting in the characteristic petal-shaped morphology. Transmission electron microscopy revealed them to be electron-dense, lobular projections without internal structure. Scanning electron microscopy demonstrated a range of morphology from rounded and intact doughnutlike structures to aggregates of irregular, loosely cohesive plates. The crystalloids were backscatter positive by backscattered electron imaging, and by x-ray microanalysis exhibited prominent calcium, phosphorus, and magnesium peaks that were not present in the adjacent tumor tissue; these three elements may be important in the formation and structure of tyrosine-rich crystalloids. The second type of crystalloid was intraductal and birefringent and was identified in 26 (12.7%) of 205 cases. In 21 of these 26 cases the crystalloids were lost on 10% formaldehyde fixation and paraffin embedding. Histochemical stains and x-ray microanalysis did not reveal a definite chemical composition, but did suggest a predominantly organic nature.

Ultrastructural morphology of secretory granules in pleomorphic adenoma of human parotid and submandibular salivary glands

Secretory granules were found in some of the cells lining the lumina of typical epithelial structures in pleomorphic adenomas. They were small, of varied electron density, and were mostly unipartite, sometimes bipartite and occasionally tripartite. They most closely resembled secretory granules of intercalary ductal cells of normal salivary glands.

Ultrastructural contributions to the study of morphological differentiation in malignant mixed (pleomorphic) tumors of salivary gland

Ultrastructural studies of pleomorphic adenoma have shown a coordinated differentiation of luminal epithelial and modified myoepithelial cells with the latter cells related to processes resulting in the myxochondroid stroma. Five examples of various histologic types of malignant mixed tumor of parotid origin were examined by electron microscopy to see if underlying patterns of tumor cell differentiation and organization matched those of pleomorphic adenoma. Whether they were intracapsular tumors (with or without identifiable pleomorphic adenoma), carcinomas ex pleomorphic adenoma, or a true malignant mixed tumor, all lesions had cell types and organizations either identical to those in pleomorphic adenoma or, as in less-differentiated examples, displayed features suggesting origin from luminal cells, myoepithelial cells, or both. Even the chondroid cells in the true malignant mixed tumor expressed ultrastructural features indicating their epithelial derivation. On the basis of these findings, some alterations to the classification and terminology of the subtypes of malignant mixed tumor are suggested.

Ultrastructural observations on luminal structures of pleomorphic adenoma of parotid and submandibular salivary glands of man

Luminal structures found in salivary pleomorphic adenomas consisted of lumina surrounded by epithelial cells that varied from being packed together to being widely separated except at the luminal margin. Communication between lumina and the surrounding stroma was occasionally seen. Secretory material and cellular debris were seen in lumina, invaginations of the luminal surfaces of periluminal cells, associated vesicles, and vacuoles. Secretory granules, lysosomes and lipofuscin were seen in periluminal cells. Secretory material and debris from necrotic periluminal cells appear to accumulate in lumina, and to be endocytosed and degraded lysosomally by periluminal cells. The finding of communications between lumina and the surrounding stroma suggests that the stromalization of the epithelium includes the luminal structures. The present investigation supports the hypothesis that many of the cellular features of the pleomorphic adenoma relate to the microenvironment.