الفهرس 
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Abstract
Salivary gland tumors are not very common and only account for less than 3% of all head and neck neoplasms.
Because salivary gland tumors are rare and so diverse, they pose a particular challenge to the surgeon and pathologist. Differentiating benign from malignant tumors may be difficult, hematoxylin-eosin (HE) staining is still the gold standard method used for diagnosing the salivary gland tumor. Immunohistochemistry (IHC) can enhance the accuracy and be a helpful tool.
Since proliferative activity is a reliable method to assess tumor biology, there has been continuous research to find such biological markers.
Recent studies have proven that the minichromosome maintenance (MCMs) protein expression has a relationship with diagnosis and prognosis. MCM-2 and MCM-3 seem to have the most important role in several types of neoplasia. Ki-67 another proliferation marker, is widely accepted for routine immunohistochemical analysis of cancer tissues.
Many studies have investigated the correlation between Ki-67 and MCM-3, they showed a strong correlation with Ki-67, although MCM-3 seemed to be more sensitive in detecting cycling cells.
The aim of this study is to evaluate the MCM-3 protein expression in benign and malignant salivary gland tumors using an immunohistochemical technique and comparing the obtained results with expression of Ki-67 proliferation antigen.
The present study was conducted on (20) cases of SGTs. For all cases, clinical data were collected as regard to sex, age, and site of tumor. The sample included (12) males and (8) females. The age range was between (26–75) years and the mean age was) 55.7) years. As regards to location, the parotid gland was the most common site, followed by the palate.
The microscopical examination showed that out of the 20 cases, 5 cases were benign salivary gland tumors (3 pleomorphic adenoma, myoepithelioma and Warthin’s tumor one case each), and 15 cases were malignant salivary gland tumors (4 mucoepidermoid carcinoma, 3 myoepithelial carcinoma, oncocytic carcinoma, adenocarcinoma and sebaceous adenocarcinoma 2case each, carcinoma ex-pleomorphic adenoma and adenoid cystic carcinoma, one case each) . Malignant tumors (75%) were more common than the benign tumors (25%), mucoepidermoid carcinoma was the most common malignant tumor (20%).
Our result showed positive immunoexpression of both ki-67 and MCM-3 in all benign and malignant tumors with different intensities. Normal salivary gland tissue showed negative immunoreactivity for the two markers (ki-67, MCM-3).
The intensity of immunostaining (in term of mean number of positive nuclei) of both markers (ki-67, MCM-3) was higher in malignant salivary gland tumors than in benign tumor.
In this study the mean number of positive nuclei for Ki-67 immunoexpression in benign and malignant neoplasms, was higher than that of MCM-3. Unpaired t test revealed that the difference was not statistically significant (p=0.234) in benign neoplasm, but the difference was statistically significant (p=0.0002) in malignant neoplasm.
The correlation between both markers in malignant salivary gland tumors was positive (R =0.4805). But, in benign neoplasms, there was negative correlation between both markers (R = -0.6653).
This study concludes that ki-67 and MCM-3 proteins are overexpressed in malignant salivary gland tumors than in benign tumor. Consequently both Ki-67 and MCM-3 may be used as diagnostic markers to distinguish benign from malignant salivary gland tumor in the challenging cases, although Ki-67seemed to be more sensitive in detecting proliferating cells.