Immunohistochemical and fluorescent microscopic study of histogenesis of salivary mucoepidermoid carcinoma

Salivary mucoepidermoid carcinoma revisited

Clinicopathological features, prognosis and therapeutic strategies for mucoepidermoid carcinoma originating in salivary and salivary-type glands of the head and neck are reviewed. We emphasise histopathological aspects, appraise the value of histochemistry, electron microscopy, immunohistochemistry and cytophotometry, and discuss histogenesis and characteristic gene translocations. We additionally consider possible diagnostic difficulties, problems related to histological grading and accuracy of existing literature, and areas of controversy or uncertainty which may benefit from further investigations.

P63 expression in papillary cystadenoma and mucoepidermoid carcinoma of minor salivary glands

OBJECTIVE

The aim of this study was to investigate the expression of p63 protein in mucoepidermoid carcinoma and papillary cystadenoma of the salivary glands, and to evaluate the usefulness of this protein in distinguishing these tumors.

STUDY DESIGN

Immunoexpression of p63 protein was studied and quantified in 9 formalin-fixed paraffin-embedded mucous retention cysts, 4 papillary cystadenomas, and 19 low-grade and 9 high-grade mucoepidermoid carcinomas.

RESULTS

All cases were positive for p63 immunoexpression; however, it was observed that p63 labeling in mucous retention cysts and papillary cystadenomas was limited to the basal layers of the cystic spaces, whereas in low-grade mucoepidermoid carcinomas, positive nuclear staining was also found diffusely in the suprabasal layers. Mucoepidermoid carcinoma presented increased immunoexpression of p63 compared with the other groups.

CONCLUSIONS

P63 immunohistochemical expression pattern can be helpful in distinguishing low-grade mucoepidermoid carcinoma from papillary cystadenoma of the salivary glands.

Comparative cytokeratin expression in the different cell types of salivary gland mucoepidermoid carcinoma

Mucoepidermoid carcinoma is the most common malignant salivary gland tumor, composed of several different cell types, with controversial histogenesis. The aim of this study was to assess the expression of cytokeratins in mucoepidermoid carcinoma, comparing to cytokeratin expression in normal salivary glands, in order to establish a possible correlation between tumor cells immunostaining and mucoepidermoid carcinoma histogenesis and differentiation. Eighty cases of salivary gland mucoepidermoid carcinoma were immunohistochemically examined with the use of antibodies against cytokeratins 6, 7, 8, 13, 14, 18, and 19. Cytokeratin expression varied according to the cellular type: squamous cells presented high expression of cytokeratins 6, 7, 8, 14, 18, and 19; intermediate and mucous cells of cytokeratin 7; clear and columnar cells of cytokeratins 6, 7, 8 and the latter also expressed cytokeratin 18. Cytokeratin 13 expression was low in all cell types. Cytokeratin immunoexpression in mucoepidermoid carcinoma was variable according to the cellular type; but regardless of the cellular type studied, cytokeratins 7 and 13 were, respectively, constantly high and low expressed. The immunoprofile of the normal salivary glands was variable according to the component but, in general, cytokeratin profile in mucoepidermoid carcinoma showed similarity to the immunoexpression on the excretory duct unit of normal salivary glands.

Mucoepidermoid carcinoma of the salivary glands. Review of the literature and clinicopathological analysis of 18 patients

Salivary gland carcinomas are a rare and clinically diverse group of neoplasms among which mucoepidermoid carcinomas (MEC) are reported to be the most frequently encountered. During the years 1994-2004 18 patients with MEC were treated in our Department. All patients underwent surgery with a curative intent, and in 11 of them treatment was supplemented by radiotherapy. Follow up ranged from 6 to 120 months. Twelve (66.6%) MECs originated from the major salivary glands with the majority located in the parotid. Histologically, 50% of tumors were classified as low grade, 28% as intermediate and 22% as high-grade MECs. Positive surgical margins were documented in six cases (33%) and all in tumors of high or intermediate histological grade. All these patients received adjuvant radiotherapy and one developed local recurrence. Local recurrence occurred in two more patients with histologically free margins. Both received postoperative radiotherapy. Distant metastases were documented in four patients all between 14 and 24 months after surgical treatment. An association between local recurrence and distant metastasis might be suggested since all patients with local recurrences subsequently developed distant metastases. The 5-year overall disease specific survival rate was 85%. Statistical multivariate analysis demonstrated that the factor that significantly correlated with overall survival was the histological grade of tumors (Log Rank test: p=0.013). A trend towards poorer survival was observed in patients aged over 50 years. Our results also suggested a potential benefit of postoperative radiotherapy for patients with positive margins.

Pathology of the salivary glands: the contribution of electron microscopy

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

Cytokeratin expression in normal and (pre)malignant head and neck epithelia: an overview

Intermediate filament proteins (IFPs) are important markers of tissue differentiation and have been receiving increasing interest, in particular, through their applicability in the characterization of malignant tumors. Cytokeratins (Cks) are a family of IFPs that are typically specific for epithelial cells. They are expressed in certain combinations depending on the type of epithelium and the degree of differentiation. This review presents a critical analysis of the available data on Ck expression in normal and (pre) neoplastic epithelia of the head and neck region. Special attention is paid to technical and cell biologic pitfalls, which can lead to false-negative or false-positive data. It appears that only a limited fraction of the reported data contributes substantially to our knowledge of IFP expression in head and neck cancer because of the use of ill-defined, often formalin-fixed and paraffin-embedded, tissue specimens, and the application of limited panels of monoclonal antibodies. It is concluded that the use of immunocytohistochemistry is promising for the differential diagnosis of head and neck tumors and contributes to our knowledge on their biologic behavior. However, documentations of more complete Ck expression patterns of normal and (pre)malignant epithelium are required, together with their correlation to clinical parameters.

Immunoprofile of mucoepidermoid carcinomas of minor salivary glands

Because the data on the antigenic phenotype of mucoepidermoid carcinoma (MEC) are incomplete and somewhat disparate, 45 MECs were evaluated immunohistochemically for low- and high-molecular-weight keratins, vimentin, glial fibrillary acidic protein, smooth muscle actin, and S-100 protein. Tumors stained uniformly for keratins and, on occasion, focally for vimentin. Tumors were nonreactive with antibodies to glial fibrillary acidic protein and, with few exceptions, to muscle-specific actins and S-100 protein. Clear cell and papillary histologic variants were seen as potential diagnostic pitfalls. If used with hematoxylin-and-eosin-stained sections, limited potential is seen for this antibody panel in surgical pathology. Myoepithelial cell-associated antigens are expressed to a very limited extent in MECs.