The ultrastructural aspects of neoplastic myoepithelial cell in pleomorphic adenomas of salivary glands

The purpose of this study has been to establish the major ultrastructural aspects of the myoepithelial cell and the myoepithelial-like cells proliferated in the pleomorphic adenomas of salivary glands. Thus, twelve benign pleomorphic adenomas of salivary glands have been studied by electron-microscopy transmission techniques. Our analysis has proved the proliferation of two major cellular populations, one of ductal type and one of myoepithelial type, which tried to reproduce the tubulo-acinar cytoarchitecture from the normal salivary glands. We have also noticed the key role of the so-called 'modified' myoepithelial cells from the periphery of the proliferating epithelial units in the genesis of the myxoid and chondromyxoid tumoral stromal areas. All these ultrastructural aspects have explained the great histological diversity of these salivary gland neoplasms as well as the key role of the myoepithelial cell in its histogenesis.

[Some particular aspects in cases of pleomorphic adenoma of the parotid gland]

Twenty three cases of parotid gland pleomorphic adenoma from Surgical Oro-Maxillo Facial Clinic of "Sf. Spiridon" Hospital, Iaşi, have been evaluated. In order to reveal the particular microscopic aspects, several histological techniques have been used: HE, Van Gieson, PAS, Alcian Blue and Gordon Sweet. The microscopic evidences points out the variety of microscopic forms even within the same case, and also the prevalence of some particular forms such as myo-epithelial cell predominance, squamous metaplasia and cystic degeneration. Our observations, corroborated with the one from other research, support the hypothesis of an unique ectodermal cell origin for the lesion histogenesis.

The frequency and distribution of mast cells in pleomorphic adenomas of salivary glands

AIM

To investigate whether the frequency and distribution of mast cells (MCs) in pleomorphic adenomas (PAs) of major and minor salivary glands justifies the suggestion that there exists an association between MCs and mucoid stromal changes in PAs.

METHODS

The material consisted of 22 cases of pleomorphic adenoma (eight arising in major and 14 in minor salivary glands) and a control group represented by five cases of monomorphic adenoma (MA). Representative 3-microm thick, paraffin-embedded sections were stained with H&E and Azur A. Computer-aided image analysis was performed in order to evaluate the relative surface area occupied by epithelial and connective tissue components, as well as the absolute number of MCs.

RESULTS

According to our findings, PAs from minor salivary glands contain significantly greater numbers of mast cells compared with tumours from major glands. Additionally, the distribution of MCs within the stromal connective tissue appeared not to be random.

CONCLUSION

It is possible that differences in the pattern of connective tissue might influence the actual concentration of MCs and that these differences are responsible for the observed variations between major and minor gland PAs.

Hyaline cell-rich chondroid syringoma: case report and review of the literature

Hyaline cell-rich chondroid syringoma (HCRCS) is a rare benign cutaneous neoplasm composed of cells with eosinophilic hyaline cytoplasm and plasmacytoid features, the origin of which remains elusive. To the best of our knowledge, only eight cases of this entity have been reported so far, and none of them was submitted to a large panel of myoepithelial markers. We report on a case of a previously healthy 29-year-old male patient who presented with a slowly enlarging flesh-colored nodule on the palmar aspect of the tenar region of his left hand, measuring 2 cm in maximum diameter. The nodule was "shelled-out" and submitted to light microscopy, immunohistochemistry, and ultrastructural examination. Histopathologic analysis disclosed a lobulated neoplasm composed of hyaline cells with plasmacytoid features showing ovoid nuclei, with occasional invaginations, finely granular chromatin, and discrete nucleoli; the cytoplasm was deeply eosinophilic with occasional dot-shaped paranuclear hyaline inclusions. On immunohistochemical evaluation, hyaline cells were strongly and diffusely positive for S-100 protein, vimentin, pan (CAM 5.2) and high molecular weight (34betaE12) cytokeratins; these cells were focally positive for GFAP, maspin, neuron-specific enolase, and cytokeratin 14. Alpha-smooth muscle actin, epithelial membrane antigen, carcinoembryonic antigen, collagen IV, Gp100 (HMB-45), and p63 were negative in neoplastic hyaline cells. Ultrastructural analysis disclosed cells with ovoid nuclei showing occasional invaginations and nuclear pockets; the cytoplasm was rich in meshworks of non-bundling intermediate filaments and a variable amount of rough endoplasmic reticulum cisternae. Based on our findings and those previously reported, hyaline cells of HCRCS might posses an aberrant myoepithelial differentiation. Most importantly, pathologists need to be aware of the histologic and immunohistochemical features of HCRCS to avoid a misdiagnosis of highly malignant neoplams, such as malignant melanoma and extra-skeletal myxoid chondrosarcoma.

Oncocytic tumor in myoepithelioma arising from the grossopalatine gland

Oncocytoma or oncocytic change in salivary glands normally occurs in old patients and mostly in the parotid gland, but those arising from the grossopalatine gland in young patients are extremely rare. The present case shows that oncocytic ductal structures were observed in myoepithelioma, consisting of spindle, plasmacytoid or epithelioid cells. The oncocytic tumor contained large amounts of eosinophilic granular cytoplasm and small nuclei.

DNA cytometry in pleomorphic adenomas with cytologic atypia

OBJECTIVE

To investigate the nuclear DNA content of pleomorphic adenomas with cytologic atypia.

STUDY DESIGN

Analysis was performed on new, fuchsin-stained samples of 10 selected cases of pleomorphic adenoma with cytologic atypia. Morphometric analysis was done by a computer-assisted image cytometry system and consisted of the determination of DNA indices, Auer DNA histogram types, and 3c and 5c exceeding rates.

RESULTS

Eight cases were diploid and two cases aneuploid according to the DNA index. The Auer histogram was type I in five cases and type III in the others. In the two aneuploid cases the 3c exceeding rate was > 10% and the 5c exceeding rate > 1%.

CONCLUSION

Atypical cells in pleomorphic adenomas with cytologic atypia carry abnormal amounts of DNA. Image cytometry can make detecting very low numbers of aneuploid cells easier due to its higher resolution as compared to that of flow cytometry.

Centrosomal abnormalities, multipolar mitoses, and chromosomal instability in head and neck tumours with dysfunctional telomeres

Carcinomas of the head and neck typically exhibit complex chromosome aberrations but the underlying mutational mechanisms remain obscure. Evaluation of cell division dynamics in low-passage cell lines from three benign and five malignant head and neck tumours revealed a strong positive correlation between multipolarity of the mitotic spindle and the formation of bridges at anaphase in both benign and malignant tumours. Cells exhibiting a high rate of mitotic abnormalities also showed several chromosome termini lacking TTAGGG repeats and a high frequency of dicentric chromosomes. Multicolour karyotyping demonstrated a preferential involvement in structural rearrangements of chromosomes with deficient telomeres. The majority of malignant, mitotically unstable tumours expressed the reverse transcriptase subunit of telomerase. These data indicate that some of the genomic instability in head and neck tumours is initiated by telomere dysfunction, leading to the formation of dicentric chromosomes. These form chromosome bridges at mitosis that could prevent the normal anaphase-telophase transition. In turn, this may cause an accumulation of centrosomes and mitotic multipolarity. Telomerase expression does not confer total stability to the tumour genome but could be crucial for moderating the rate of chromosomal evolution.

Pleomorphic adenocarcinoma of the ciliary epithelium: a clinicopathological, immunohistochemical, ultrastructural, DNA-ploidy and comparative genomic hybridization analysis of an unusual case

PURPOSE

To describe detailed phenotypic and genotypic analysis of a pleomorphic adenocarcinoma of the ciliary epithelium (CE).

CASE REPORT

An 86-year-old white woman developed an enlarging mass protruding from her previously eviscerated left eye 2 months postoperatively. Based on light and ultrastructural microscopy, the final diagnosis was a pleomorphic adenocarcinoma of the ciliary epithelium (CE).

DISCUSSION

Cell proliferation indices confirmed the unusually rapid growth rate of this tumor; the peridiploid DNA content might explain the relatively low incidence of distant metastases. An imbalance of the chromosome 6 was also found by Comparative Genomic Hybridization (CGH).

Lipomatous mixed tumour of the skin: a histological, immunohistochemical and ultrastructural study

BACKGROUND

Mixed tumours are composed of an admixture of an epithelial/myoepithelial and usually a myxochondroid stromal component. Adipocytes are found more rarely, and account for a minor part of the tumour. To date, only three cases of mixed tumour/pleomorphic adenoma of the salivary gland have been described, showing an extensive adipocyte content of more than 90% of the tumour tissue. Owing to this peculiarity, some authors have defined it as 'lipomatous pleomorphic adenoma'. We are not aware of previously reported similar lesions in the skin.

OBJECTIVES

We report a case of a tumour that occurred as a 2 x 2 x 1.5 cm nodule in the scalp of a 65-year-old man. Analogies with salivary lipomatous pleomorphic adenoma, as well as histogenesis and differential diagnoses are discussed here.

METHODS

A histological, immunohistochemical and ultrastructural study was performed.

RESULTS

The tumour was well-circumscribed and showed a substantial mature adipose tissue component intermingled with epithelial cells arranged in ducts and branching tubules, embedded in a fibromyxoid stroma, which was diagnostic of a chondroid syringoma/mixed tumour. Adipocytes strongly expressed S-100 protein and cytokeratin 14. Transitional elements from epithelial/myoepithelial cells into adipocytes were observed. They coexpressed cytokeratin 14, S-100 protein and vimentin, and showed lipid droplets, desmosome-type junctions, cytoplasmic tonofilaments and basal lamina.

CONCLUSIONS

The tumour differed from lipomas with myxoid stroma and from lipoadenomas, which show non-proliferating normal sweat glands admixed with adipose tissue. Because of the similarity to lipomatous pleomorphic adenoma/mixed tumour of salivary glands, we suggest that it should be called 'lipomatous mixed tumour of the skin'.

Recurrent malignant chondroid syringoma of the foot: a case report and review of the literature

Malignant chondroid syringoma, or mixed tumor of the skin, salivary gland type, is an uncommon neoplasm believed to originate in sweat glands. This neoplasm occurs mostly in women and is typically seen in the extremities and torso. A case of recurrent malignant chondroid syringoma of the right foot in a man aged 34 years is described with a review of pertinent literature. The surgically excised neoplasm was evaluated by routine histology, immunohistochemistry, and transmission electron microscopy. The malignant chondroid syringoma showed microscopic dermal satellite tumor nodules. Immunohistochemical staining was positive for keratin and S100 and negative for actin and p53. Ki-67 showed <10% positive staining. Ultrastructurally, the neoplasm was composed of epithelial cells with tonofilaments, cell junctions, and electron-dense amorphous keratin-like substance in the intercellular spaces. No evidence of myoepithelial differentiation was noted. Given the tumoral size, acral location, and histologic findings, the neoplasm was classified as a malignant chondroid syringoma. After reviewing the literature, it became apparent that wide surgical excision, adjuvant radiation therapy as well as patient education are critical in facilitating long-term survival.

[An electron microscopic histochemical study on the fibrous formation in pleomorphic adenoma of the salivary gland]

OBJECTIVE

To study the kinds of fibers and mechanism of fibrous formation in myxochondroid tissue of pleomorphic adenoma.

METHODS

Eight cases of pleomorphic adenomas of salivary gland were studied by histological and electron microscopic histochemical techniques.

RESULTS

The histological study showed that collagenous fibers and elastic fibers which constituted the trestle were distributed in myxochondroid areas of pleomorphic adenoma. The electron microscopic histochemical study showed that the myxochondroid tissue contained slender collagen fibrils measuring 50 nm in diameter and heavily stained elastic fibers. In cytoplasm of the myxochondroid cells two types of the Golgi-derived vesicles were seen: one was small round vesicles with a uniform electron dense core of amorphous material and heavily stained; another type was small round vesicles with a non-uniform electron dense core of filamentous material and stained grey. These materials were released into the extracellular space by cytoplasmic exocytosis.

CONCLUSIONS

Neoplastic myoepithelial cells have the ability to synthesize and secrete procollagen and precursor of elastin, thus forming collagenous fibers and elastic fibers in myxochondroid areas.

Biosynthesis of glycosaminoglycans and aggrecan by tumor cells in salivary pleomorphic adenoma: ultrastructural evidence

The present study attempted to discover the sites of synthesis of various glycosaminoglycans (GAGs) and aggrecan in salivary pleomorphic adenoma (PA) with the use of a highly sensitive and specific post-embedding immunogold-silver staining technique at the ultrastructural level. Silver particles representing various GAGs and aggrecan were found to accumulate frequently in the intercellular spaces of non-luminal cells in the epithelial clusters and were dispersed in the myxoid matrix of the mesenchyme-like areas. Furthermore, the non-luminal epithelial cells were demonstrated to contain immunopositive intracytoplasmic vesicles and vacuoles, some of which were of Golgi complex origin. In contrast, intracellular silver particles for hyaluronic acid were mostly attached to the inner surface of the cell membrane. These observations agree well with the current theories of the biosynthesis of GAGs and proteoglycans and provide direct evidence for the production of various GAGs and aggrecan by tumor epithelial cells of PA. Such findings support the ideas that in PA a loss of epithelium occurs by stromalization following epithelial secretion of extracellular matrix substances and transformation of epithelium to mesenchyme represents the basic principle of the tissue heterogeneity in this tumor.

Malignant plasmacytoid myoepithelioma of the palate: histological observations compared to benign predominant plasmacytoid myoepithelial cells in pleomorphic adenoma of the palate

Predominant benign plasmacytoid myoepithelial cells in pleomorphic adenoma and malignant plasmacytoid myoepithelioma cells were investigated morphologically. The cells of both tumors were plasmacytoid in appearance and sheet-like. Immunohistochemically, they were positive for keratin, vimentin, and S-100 protein, and negative for alpha-smooth muscle actin. In the malignant cells, large nuclei with irregular nuclear membranes and distinct nucleoi and occasional intranuclear inclusions and nuclear grooves were seen. Ultrastructural findings showed that the benign cells were richer in intermediate filaments and had fewer mitochondria. The intranuclear inclusions and nuclear grooves of the malignant cells were caused by invagination of the irregular nuclear membranes. Taken in their entirety, the above light microscopical nuclear findings may be useful as an adjunct for distinguishing malignant from benign plasmacytoid neoplastic myoepithelial cells of the salivary gland.

Effect of spatial arrangement of the basement membrane on cultured pleomorphic adenoma cells. Study by immunocytochemistry and electron and confocal microscopy

In a cell line from human pleomorphic adenoma (AP2 cells) we studied the response of these cells to basement membrane proteins. The culture was characterized as myoepithelial-like by transmission electron microscopy and immunocytochemistry. AP2 cells were grown in contact with a reconstituted basement membrane (Matrigel). Cells grown on Matrigel showed conspicuous phenotypic alterations, depending on how the substrate was applied. Cells grown on the top of Matrigel developed a dendritic phenotype, exhibiting thin, long and intercommunicating cytoplasmic extensions resembling normal myoepithelial cells. Cells grown inside Matrigel formed multi-layered clusters. Light, confocal and transmission electron microscopy showed that these clusters were formed by double-layered epithelioid cells delimiting luminal spaces. The cells facing the lumen were cuboidal, showing microvilli at the apical plasmalemmal and junctional complexes. The spatial arrangement of basement membrane is a key modulator of morphogenetic changes and cytodifferentiation of tumour myoepithelial cell lineage in culture.

Case of myoepithelioma originating from the palate: collagenogenesis in myoepithelial tumor cells

We report a case of myoepithelioma of the palate in a 53-yr-old man. Myoepithelioma cells consisting of both plasmacytoid type and spindle type were obtained. A reticular pattern composed of a mosaic arrangement of hyaline-like abundant cytoplasm, and scant matrix and considerable fiber formation were characteristic features of the plasmacytoid type; granular cytoplasm and a snake-like shape were characteristic features of the spindle type. These are important points in differentiating this tumor from cellular type pleomorphic adenoma. The present study shows that tumorous myoepithelial cells can synthesize and secrete extracellular components such as proteoglycans, basal lamina, collagen fibers, and elastic fibers.

Fine-needle aspiration biopsy of adenoid cystic carcinoma of the breast: a case report

We describe the cytologic findings of a fine-needle aspiration (FNA) breast lesion with a typical histology for adenoid cystic carcinoma. The aspirate yielded highly cellular smears with a monomorphic population of small, slightly atypical cells, arranged in multilayered groups with abundant fine intercellular metachromatic substance between cell groups. There were also fragments of fibrillar stroma in close relation to epithelial cells. The diagnosis based on the FNA material was suspicious of malignancy. The cytomorphology in this case presented a difficult differential diagnosis with pleomorphic adenoma. Features indicative of adenoid cystic carcinoma were nuclear cell hyperchromasia, the presence of small nucleoli, and scant, poorly defined, or absent cytoplasms. Differential diagnosis of breast adenoid cystic carcinoma with other entities will also be discussed.

[Histochemical and electronic microscopical studies of stellate fibrillar formations (SFF) in salivary gland tumors]

PURPOSE

To study the structure and significance of SFF in pleomorphic adenoma and myoepithelioma.

MATERIAL AND METHODS

Tow cases of each tumor were studied. Histologie and ultrathin sections were made, stained with HE, Mallory, Van Gieson, Pollak methods, and examined with light and transmission electronic microscopes. RESULTE: The SFF were proved to be formed by radial arrangement of collagen fibers, which were composed of striped fibrillae under TEM.

CONCLUSION

The structure of the SFF is understood, their existence may play a role the pathologic diagnosis.

Pleomorphic adenoma of the bronchus

An example of pleomorphic adenoma of the bronchus is described in a 27 year old male student who was referred for evaluation of a coin lesion identified incidentally on chest x ray. The tumour exhibited the classic histological, immunohistochemical and ultrastructural features of this rare entity but, in addition, contained mature and immature adipose tissue in the stroma and showed transition, in its superficial portion, between ostensibly normal bronchial mucus glands and tumour tubules. Neither of these features has been commented upon previously.

A fluorescence in situ hybridization (FISH) analysis with centromere-specific DNA probes of chromosomes 3 and 17 in pleomorphic adenomas and adenoid cystic carcinomas

Aberrations of chromosomes 3 and 17 were studied by FISH using centromere-specific DNA probes in 11 salivary adenoid cystic carcinomas (ACC) and 8 salivary pleomorphic adenomas (PA), with 3 lymph nodes as controls. Two hybridized signals were detected in 92.8 +/- 2.7% of controls, 73.2 +/- 7.0% of PA and 66.8 +/- 7.9% of ACC cells for chromosome 3, and in 90.4 +/- 2.3% of controls, 59.5 +/- 25.0% of PA and 44.8 +/- 20.2% of ACC for chromosome 17. More than 3 hybridized signals, which indicate polysomy, were observed in 3.1% of controls, 15.5% of PA and 22.9% of ACC cells for chromosome 3, and in 1.2% of controls, 10.3% of PA and 23.1% of ACC cells for chromosome 17. A single hybridized signal was much more frequent for chromosome 17 than for chromosome 3. These findings suggest that polysomy of both chromosomes occurs during the development of salivary gland tumors, and its frequency is increased in adenoid cystic carcinoma as compared to pleomorphic adenoma. In addition, monosomy of chromosome 17 could possibly be significant in salivary gland tumors.

[Histogenesis of pleomorphic adenoma of the salivary gland]

Six parotid pleomorphic adenomas were studied histochemically by electron microscopy after staining with ruthenium red. It was found that the myxoid region was filled with ruthenium red granules. Similar positive ruthenium red-stained intracellular granules were observed within the Golgi-derived vacuoles of the neoplastic myoepithelial cells in the myxoid region. Some cells located at the periphery of the double-layer ductal structure had the features of myoepithelial cell, they also showed similar positive ruthenium red-stained granules in the intracellular vacuoles and intercellular space. No ruthenium red-stained granules was obtained in neoplastic ductal epithelium and the mucus in ductal cavities were negative for ruthenium red stain. The observations indicate that the neoplastic myoepithelial cells in the myxoid region probably derive from the periphery of the double-layer ductal structure, they secrete the proteoglycans forming the myxoid region and play an important role in the histogenesis of pleomorphic adenoma.

[Myoepithelial adenoma of palate minor salivary gland]

A case of myoepithelial adenoma of hard palate minor salivary glands is reported. This is a very rare tumor. Histological, clinical and therapeutical aspects are discussed and a literature review is carried out.

Pleomorphic adenoma of the lacrimal gland manifesting as exophthalmos in adolescence--case report

A 16-year-old girl presented with a pleomorphic adenoma of the lacrimal gland manifesting as left painless exophthalmos which had persisted for 3 years. Computed tomography revealed a tumor about 15 mm in diameter in the superolateral site of the left orbit. The tumor was removed completely by combined orbitofrontal craniotomy through a transcranial approach. Histological examination demonstrated the growth of tumor cells as glandular cavities or sheets, with myxoid and partly chondroid connective tissue stroma. Pleomorphic adenoma of the lacrimal gland is unusual in adolescents.

Familial occurrence of pleomorphic adenoma

Pleomorphic adenoma is the most common neoplasm found in the parotid gland. The familial occurrence of any salivary gland neoplasm is rare. There are 8 previous reports in the literature of familial occurrence of salivary gland tumors. Two of these report the occurrence of pleomorphic adenoma of the parotid gland in siblings; all 4 patients were adults. We report here an 11-year-old male who presented with a left parotid mass and underwent parotidectomy. The mass proved to be a pleomorphic adenoma. His sister presented 9 years later at the age of 15 years with a similar mass also in the left parotid area. She underwent superficial parotidectomy which revealed the mass to be a pleomorphic adenoma. We believe these are the youngest siblings reported to date in which familial pleomorphic adenoma has occurred.

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.

[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.