The immunohistochemical features of 16 cases of papillary cystadenocarcinoma of salivary glands using a panel of monoclonal and polyclonal antibodies were evaluated. The specimens were from patients postoperatively diagnosed as papillary cystadenocarcinoma of salivary glands where the age of the patients ranged from 20-70 years, males were more commonly affected than the females and parotid gland was the most commonly affected site. The cytokeratins detected by MoAb KL1 and K8.12 were positive in all cases showing a heterogeneity in intensity of reaction. A coexpression of vimentin with cytokeratin was found in 10 cases. The tumor cells had a coexpression of S-100 protein and neuron specific enolase (NSE). Glial fibrillary acidic protein (GFAP) was positive in one case with multiple expression of cytokeratins, vimentin NSE, S-100 protein. The polymorphic mucin MAM-6 was positive in all cases and MAM-3 in 8 cases showing different intensity of reaction. The tumor cells were positive for lysozyme (8 cases), lactoferrin (10 cases) and alpha-1-antichymotrypsin (10 cases). The immunoreactive c-erbB-2 oncoprotein on the cell surface membrane was detected in 2 cases. The labeling index of proliferating cell nuclear antigen in the tumor cells ranged from 3.8 to 43.2% (mean 14.2 +/- standard deviation 9.8). Histopathological feature and a heterogeneity of multiple expression of tissue markers may suggest that a population of cells in papillary cystadenocarcinoma may be counterparts of modified myoepithelial cells of pleomorphic adenoma that express epithelial, mesenchymal and neuronal differentiation although the role of myoepithelial cells in the genesis of this tumor is not clear. However, disorganized stratification and malignant transformation of ductal cells may be the most likely possibility in the histogenesis of this tumor.

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