Immunohistochemical expression of epidermal growth factor receptor in salivary gland tumours

Summary Immunohistochemical localization of epidermal growth factor receptor (EGFR) in normal salivary glands and tumours (108 cases) was studied using a monoclonal antibody. In the normal salivary glands, EGFR was occasionally detected in ductal segments of intercalated, striated, and excretory ducts, but not in acinar cells. The frequency of positive EGFR staining in salivary gland tumours was not high: pleomorphic adenoma, 33.8%; mucoepidermoid tumour, 25.0%; adenolymphoma, 44.4%; and sialoadenocarcinoma, 66.6%. Pleomorphic adenomas showed positive staining for EGFR on the luminal side of luminal cells and in squamous metaplastic cells of tumour tissue. Some modified myoepithelial cells were also reactive whereas outer spindle tumour cells were unstained. Adenolymphomas regularly exhibited positive EGFR staining in the cell membrane; mucoepidermoid carcinoma displayed positive staining in cell membranes in epidermoid tumour cells and cytoplasmic staining in mucous-secreting tumour cells. Sialocarcinomas revealed cell membrane staining and whole cytoplasmic staining for EGFR. The immunohistochemical localization of EGFR could be classified into two types, one the cell membrane-positive type found in epithelial tumour cells, and the second the cytoplasmic positive type seen in normal ductal cells, the luminal tumour cells of pleomorphic adenomas and mucous-secreting tumour cells.     

Immunohistochemical distribution of human epidermal growth factor in salivary gland tumours

Summary Immunohistochemical identification of human epidermal growth factor (hEGF) was carried out in a total of 152 cases of salivary gland tumours, consisting 107 pleomorphic adenomas and their variants, 13 adenolymphomas and 32 adenoid cystic carcinomas. A high percentage of pleomorphic adenomas revealed markedly positive hEGF staining of the luminal surface cells of tubuloductal structures and of modified or neoplastic myoepithelial cells. Clear cells of the tumour showed various reactivities from very slight to strong. Eosinophilic epithelial cells of adenolymphoma gave a positive reaction for hEGF in all the cases, whereas most adenoid cystic adenoma lacked hEGF staining; however some cases showed positive staining of the tumour cells. The immunohistochemical detection of hEGF in most salivary gland tumours suggests this factor to be a possible new marker of salivary glands tumours, and to have a biological role in tumour proliferation.     

Congenital tumours of the salivary gland: a case report and review

A congenital epithelial tumour of the submandibular salivary gland, occurring in a child of 10 months, is described. The lesion appeared benign and consisted of basal type cells, showing ductal and acinar differentiation with myoepithelial cells. The associated fibrous stroma contained blood vessels and small nerve bundles. A few similar lesions have been reported in the past, some of which showed features of malignancy. Although various names have been proposed, we suggest that these lesions represent a single group derived from a primitive cell line and advocate the use of the term sialoblastoma.     

Tenascin in salivary gland tumours

Summary The distribution of tenascin immunoreactivity was analysed in salivary gland tissue and in various benign and malignant tumours of the salivary gland. In the non-neoplastic tissue, tenascin was seen in the areas of basement membranes of the ductal epithelium. No immunoreactivity could be observed in the serous or mucous glands. In pleomorphic adenomas, tenascin immunoreactivity could be seen in the stromal compartment. It was more pronounced in the dense stromal areas and chondroid elements than in the myxoid area. In Warthin's tumours, strong tenascin immunoreactivity could be observed in the basement membrane zone of the epithelial component. In the lymphatic component, faint reticular staining could be seen. In adenoid cystic carcinomas, acinic cell tumours and mucoepidermoid carcinomas, tenascin showed a linear stromal distribution. No intracytoplasmic immunoreactivity could be seen in any of the cases. The widespread tenascin positivity in salivary gland tumours suggests that tenascin may play a role in the induction and progression of salivary gland tumours, presumably by interfering with the normal parenchymal-mesenchymal interaction.     

Diagnostic and prognostic biomarkers in salivary gland tumours

Salivary glands are a heterogeneous group of neoplasms and are diagnostically challenging with overlapping microscopic features between tumours as well as intra-tumour morphological diversity. Correct diagnosis is essential to ensure appropriate management and follow-up. Morphological and cytological analysis of haematoxylin and eosin stained tissue sections is supplemented by a large number of immunohistochemical and special stains as well as molecular rearrangements. A broad literature search was performed to provide an overview of all biomarkers used for diagnosis and prognosis prediction of salivary gland tumours. The wide range of biomarkers reported in the literature can be overwhelming but used in the correct context can aid diagnosis and predict the behaviour of these challenging tumours. They can also help identify recently described new entities.     

Advances in salivary gland pathology

This review summarizes the new findings on salivary gland pathology under the following categories: immunohistochemistry; molecular genetics; newly recognized tumour types; known tumour entities with new findings; and progression of salivary gland tumours. In the application of immunohistochemistry, CD117 can aid in highlighting the luminal cell component of various salivary gland tumours, whereas p63 or maspin can aid in highlighting the abluminal cell component. A high Ki67 index remains the most useful marker to predict adverse outcome in salivary gland carcinoma. Specific chromosomal translocations are recognized in pleomorphic adenoma (with translocation involving PLGA1 or HMGA2 gene) and mucoepidermoid carcinoma (with MECT1-MAML2 gene fusion). Newly recognized entities include: sclerosing polycystic adenosis (with recent molecular evidence supporting its neoplastic nature), sclerosing mucoepidermoid carcinoma with eosinophilia, keratocystoma, adenoma with additional stromal component (lymphadenoma, lipoadenoma and adenofibroma), cribriform adenocarcinoma of the tongue and signet ring adenocarcinoma of minor salivary gland. Known tumour entities with new findings include: salivary duct carcinoma (with newly recognized mucinous, micropapillary and sarcomatoid variants), intraductal carcinoma (with controversies in terminology), mucoepidermoid carcinoma (with newly proposed grading parameters and oncocytic variant), epithelial-myoepithelial carcinoma (with newly recognized morphological variants), small cell carcinoma (with most cases being related to Merkel cell carcinoma), extranodal marginal zone B-cell lymphoma (with specific chromosomal translocation) and chronic sclerosing sialadenitis (being a component of IgG4-related sclerosing disease). Progression of salivary gland tumours can take the form of malignant transformation of a benign tumour, progression from low-grade to high-grade carcinoma, dedifferentiation, or stromal invasion of an in situ carcinoma.     

Localization of prostate-specific antigen-like immunoreactivity in human salivary gland and salivary gland tumors

Immunoreactivity of prostate-specific antigen (PSA), a kallikrein-like enzyme present in the seminal plasma, was demonstrated by indirect immunoperoxidase staining using a PSA antiserum in the apical cytoplasm along the luminal border of small-sized duct epithelial cells of the major salivary (parotid and submandibular) gland of both sexes (56/56, 100%). No PSA-like immunoreactivity was seen in large-sized duct epithelial cells and acinar cells. Minor salivary gland ducts were negative. When inflammatory and atrophic changes were observed, ductal expression of PSA-like immunoreactivity was decreased (12/37, 32%) and the site of intracellular localization often became diffusely cytoplasmic. The immunoreactivity was absorbed by human seminal plasma. Immunoreactivities of prostatic acid phosphatase and sex hormone receptors were undetectable in the salivary gland. Twenty-nine (34%) of 86 salivary gland tumors with ductal differentiation were immunoreactive for PSA mainly in the cytoplasm. A PSA monoclonal antibody ER-PR8 detected immunoreactivity in the prostate but not in the salivary glands or their tumors. Prostate-specific antigen-like immunoreactivity in small-sized (intercalated) duct epithelial cells of the major salivary gland and their tumors may be due to cross-reactivity of the antiserum with kallikrein-like substances.     

Immunohistochemical localization of the bone morphogenetic protein-6 in salivary pleomorphic adenomas

Salivary pleomorphic adenomas are often associated with chondroid tissue formation. We have found that bone morphogenetic proteins (BMP), especially BMP-2, may play an important role in ectopic chondrogenesis in this tumor. Bone morphogenetic protein-6 was reported to be related to the osteogenic metastasis of prostatic carcinomas. The relationship between BMP-6 expression and chondroid tissue formation is investigated. Twenty-three pleomorphic adenomas were examined immunohistochemically. The overexpression of BMP-6 was observed in 10 pleomorphic adenomas of the major salivary glands (43. 5%), and no evidence of BMP-6 expression in any of the nine pleomorphic adenomas of the palate. Bone morphogenetic protein-6 was immunolocalized in the lacuna cells of the chondroid tissue, in which type II collagen was localized. Bone morphogenetic protein-6 was expressed in inner ductal cells of the tubulo-glandular structures in the pleomorphic adenomas. This finding indicates that BMP-6 may be associated with the differentiation of inner ductal cells. Bone morphogenetic protein-6 was expressed weakly in neoplastic myoepithelial cells in the myxoid areas, which may be related to the production of extracellular matrices. Bone morphogenetic protein-6 has a role in chondroid formation, and also tubulo-glandular differentiation in pleomorphic adenomas. In conclusion, a large portion of pleomorphic adenomas of the salivary gland origin, but not of palate origin, was shown to overexpress BMP-6 protein.     

MUC1 and MUC2 expression in salivary gland tumors and in non-neoplastic salivary gland tissue

The expression of MUC1 and MUC2 was studied in salivary gland tumors and non-neoplastic salivary gland tissue. Formalin-fixed paraffin-embedded specimens from 101 patients (21 pleomorphic adenomas (PA), 22 Warthin's tumors (WT), 26 adenoid cystic carcinomas (ACC), 13 acinic cell adenocarcinomas (ACA), 9 mucoepidermoid carcinomas (MC), and 10 specimens of non-neoplastic parotid and submandibular gland tissue) were immunostained. All salivary gland tumors expressed MUC1. A strong immunoreactivity was noted in WT and MC, a moderate in ACC and ACA, and a weak in PA. Strong expression of MUC2 was noted in all WT, moderate expression in MC, and weak expression in PA and ACA. All cases of ACC except for two were negative for MUC2. In general, MUC1 expression was stronger than that of MUC2. Non-neoplastic salivary gland tissue revealed a moderate MUC1 and MUC2 expression in excretory ducts and a strong expression in striated ducts. The apical plasma membrane of some serous acini expressed MUC1. Mucous acini were negative for both antigens. No change in immunoreactivity was noted in cases of chronic sclerosing sialadenitis. In conclusion, the different expression pattern of MUC1 and MUC2 in salivary gland neoplasia may be of additional value for the classification of salivary gland tumors.     

Immunohistochemical expression of amelogenins in odontogenic epithelial tumours and cysts

Summary Amelogenins, enamel proteins in odontogenic tumours, were detected immunohistochemically using a monoclonal antibody. They were strongly expressed in amyloid-like material, ghost cells, and the cells surrounding ghost cells of calcifying epithelial odontogenic tumours and cysts, whereas calcified bodies within the tumours and cysts showed negative staining. The expression of amelogenins was also positive in tumour cells of ameloblastoma, adenomatoid odontogenic tumour, squamous odontogenic tumour and ameloblastic fibroma. Peripheral tumour cells of the follicular ameloblastoma were positive with relatively intense staining. Undifferentiated or flattened tumour cells of adenomatoid odontogenic tumour and non-keratinized tumour cells of the squamous odontogenic tumour showed marked staining. Reduced ameloblasts in the odontoma displayed the strongest staining for amelogenins. The study suggests that biosynthesis of amelogenins may occur in the homogeneous materials of calcifying epithelial odontogenic tumours and cysts.     

Lowp53 protein expression in salivary gland tumours compared with lung carcinomas

Summary Fifty-one salivary gland tumours (23 pleomorphic adenomas, 5 Warthin's tumours, 12 mucoepidermoid carcinomas, 7 adenoid cystic carcinomas, 3 undifferentiated carcinomas and 1 acinic cell tumour) and 27 lung carcinomas (18 squamous cell carcinomas, 6 adenocarcinomas and 3 small cell carcinomas) were analysed immunohistochemically for the expression ofp53 nuclear phosphoprotein. Eight out of 51 (16%) salivary gland tumours werep53 positive. Three of these were benign and 5 malignant. All 3 benign salivary gland tumours were pleomorphic adenomas and expressed only occasional nuclear positivity with less than 1% of tumour cells positive. Of the 5p53-positive malignant tumours, 3 were mucoepidermoid carcinomas and 2 undifferentiated carcinomas. The malignant salivary gland tumours expressed more than 1% of positive nuclei in every case. Seventeen lung carcinomas werep53 positive (63%). Thirteen of these were squamous cell carcinomas, 3 were adenocarcinomas and 1 small cell lung carcinoma. The results show that mutations of thep53 gene may be infrequent in salivary gland tumours when compared with lung carcinomas. The relatively indolent course of some histological types of malignant salivary gland tumours could be associated with the preservation of the non-mutatedp53 gene in most of these tumours. The presence ofp53 positivity in some pleomorphic adenomas might, on one hand, suggest thatp53 gene alterations are also present in these tumours; on the other hand, the accumulation of thep53 protein in these tumours might also be due to some unknown mechanism, not necessarily related top53 gene mutation.     

Immunohistochemical study of carbonic anhydrase in mixed tumours from major salivary glands and skin

Summary Immunohistochemical distribution of carbonic anhydrase isoenzyme I and II was studied in mixed tumours of major salivary glands and skin. The normal salivary glands displayed strong carbonic anhydrase activity in both ductal epithelium and serous acinar cells and the serous demilune cells in the submandibular glands, including the eccrine ducts. Pleomorphic adenoma salivary gland origin exhibited positive staining in the innerlayer of epithelial cells of tubular, duct-like and glandular structures. No enzymatic staining was noted in the outer layer of tumour cells in these structures. Spindle tumour cells or the fibroblast-like cells with long cytoplasmic processes identified in the adjacent hyalin and myxomatous stroma were rarely positive, while chondroidal and osteo-chondroidal cells were highly reactive. Mixed tumours of eccrine gland origin showed the most reactive staining cells scattered throughout neoplastic epithelium in all tissues examined. Immunohistochemical stainability was usually higher for carbonic anhydrase II than I for both normal and tumour tissues. The biological roles of the distribution profiles of carbonic anhydrase are discussed.This investigation was supported partially from Miyata Research fund     

Basement membrane proteins in salivary gland tumours

Summary Immunohistochemical localization of type IV collagen and laminin in normal salivary glands and in salivary gland tumours of various types was studied using rabbit antisera. In normal salivary glands, type IV collagen and laminin were co-localized in basement membranes surrounding acini, ducts, fat cells and peripheral nerves. In salivary gland tumours, three main patterns of co-expression of these basement membrane proteins were distinguished. Linear basement membrane-like staining was detected in duct-cell-derived benign salivary gland tumours and in acinic cell carcinomas. In invasive lesions, however, these basement membrane proteins were distributed in an irregular, interrupted manner, and in many cases they were completely absent. Both benign and malignant salivary gland tumours which have a prominent myoepithelial cell component display a particular deposition of basement membrane molecules adjacent to the modified myoepithelial cells, and at the margins of extracellular matrix deposits within these tumours.     

Phenotypic expression of human epidermal growth factor in foetal submandibular gland and pleomorphic adenoma of salivary gland

Summary The phenotypic expression of the human epidermal growth factor (EGF) was investigated immunohistochemically in human foetal submandibular glands from the 5th to 10th month of gestation, adult normal submandibular glands and 48 cases of pleomorphic adenomas. In foetal submandibular glands, both the terminal buds and primary ducts at the intermediate stage of gestation were positive for EGF, and in particular, the outer layer cells of primary ducts showed strong EGF-immunoreactivity. EGF-positive cells decreased as the gestational stage advanced and only ductal cells were weakly positive for EGF at the terminal stage of gestation. In the adult normal submandibular gland, weak immunoreactivity for EGF was restricted to ductal cells. However, 41 (86%) of the 48 pleomorphic adenomas had EGF-positive cells which were distributed among the ductal, chondroid and myxoid portion. No EGF-immunoreactivity was detected in the solid portion of pleomorphic adenomas. These results suggest that EGF may play an important role in the growth and differentiation of foetal cells as well as the proliferation of tumour cells in pleomorphic adenomas.     

Immunohistochemical localization of endothelin-1 in non-neoplastic and neoplastic adrenal gland tissue

Endothelin (ET)-1 is a 21-amino acid peptide with potent vasopressor and vasocontrictive properties. Biochemical studies suggest that this peptide occurs in adrenal glands, where it influences steroid hormone production. However, we have found no report of the topographical distribution of this peptide. The localization of ET-1 immunoreactivity in non-neoplastic (37 cases) and neoplastic adrenal glands (48 cases) was investigated with a sensitive immunohistochemical technique applied to routinely processed tissue specimens. ET-1 immunoreactivity was regularly seen in the cortex, especially in the zona fasciculata and to a varying extent also in the other two zones, but not in the medulla. The immunoreactive material appeared in the cytoplasm mostly in the form of vacuolar structures but also as grains. Focally, the cell membrane also showed immunoreactive staining. In the zona reticularis the immunoreactivity appeared mainly as cytoplasmic grains. Most cortical adenomas displayed numerous immunoreactive cells. The immunoreactivity in the tumour tissue appeared in the same forms as in normal cortex, but the reactive products were generally fewer in number. No obvious differences in immunostaining were seen between the aldosterone- and cortisol-producing adenomas or the non-functioning ones. Three of the ten carcinomas contained immunoreactive cells, but they were few, appearing focally and the ET-1 immunoreactive structures were seen as dust-like material. The difference in immunoreactivity between the benign and the malignant cortical neoplasms may be of diagnostic value. Functionally our results support a relationship between ET-1 and steroid regulation in non-neoplastic cortical tissue.     

Unique expression of MUC3, MUC5AC and cytokeratins in salivary gland carcinomas

The differential diagnosis of salivary gland carcinoma is often difficult because of the confusing histopathological features of the different types of salivary gland carcinomas. The expression of MUC3, MUC5AC, MUC6, cytokeratin (CK)7 and CK20 was studied in 20 mucoepidermoid carcinomas (MEC), 20 adenoid cystic carcinomas (AdCC), and 11 acinic cell carcinomas (ACC). All the cases (51/51, 100%) were positive for CK7, but they were not positive for CK20. All the cases (100%) of the MEC were positive for MUC5AC, while all MEC (100%) were negative for MUC3. Only two cases (10%) were positive for MUC6. All cases (100%) of AdCC were negative for MUC3, MUC5AC and MUC6. Eight cases (73%) of ACC were positive for MUC3, but all the cases (100%) were negative for MUC5AC and MUC6. It is concluded that the positive expression of MUC5AC is very unique to MEC, and that the positive expression of MUC3 is very unique to ACC. These findings will be very useful for the differential diagnosis of the salivary gland carcinomas.