الفهرس 
REVIEW OF LITERATUREOnly 14 pages are availabe for public view
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Abstract
Salivary gland tumors (SGTs) are a heterogenous group of neoplasms. They are characterized by a complex nature owing to variations in their biological behaviours, morphological patterns and histologic diversity. Thus, diagnosis of such tumors is challenging. The decision of diagnosing a SGT as benign or malignant is serious because it affects the extent of surgery.
Insulin like growth factor II mRNA binding protein 3 (IMP3) belongs to IMP family which consists of IMP1, IMP2 and IMP3. IMP family members are important in RNA processing. IMP3 is expressed in many organs during embryogenesis, however traces of it may be expressed in normal adult tissues. IMP3 plays an important role in cell growth, proliferation, adhesion and migration. It is expressed in various human cancers and its expression has been linked to poor prognosis and survival in these malignancies. Furthermore, IMP3 is minimally expressed in benign tumors or not expressed at all. Therefore, it is considered a valuable diagnostic and prognostic marker.
The role of IMP3 in SGTs is still not confirmed due to the very limited studies carried out on this type of tumors. The aim of the present study was to assess the expression of IMP3 in benign and malignant SGTs and to correlate its expression was the histological grade of malignant SGTs.
Forty-four cases of SGTs were included in the present study. Twenty cases were benign (eight cases of pleomorphic adenoma, four cases of each of Warthin’s tumor and myoepithelioma, two cases of each of basal cell adenoma and oncocytoma), and twenty-four cases were malignant (six cases of mucoepidermoid carcinoma, four cases of each of adenoid cystic carcinoma and carcinoma ex pleomorphic adenoma, two cases of each of acinic cell carcinoma, salivary duct carcinoma, myoepithelial carcinoma, basal cell adenocarcinoma and oncocytic carcinoma).
Malignant SGTs (54.5%) were more common than benign SGTs (45.5%). The most common SGT was pleomorphic adenoma representing 18.2%. Mucoepidermoid carcinoma came second in order representing 13.6%. The patients’ age ranged between 12 and 73 years. Twenty-one patients (47.7%) were males and twenty-three patients (52.3%) were females. Regarding the location, the most common site was the palate (45.5%) followed by the parotid gland (38.6%).
Biopsies were histologically evaluated using Haematoxylin and Eosin staining. Serial sections were immunohistochemically stained by rabbit monoclonal antibody IMP3 using Labeled- Strept -Avidin Biotin (LSAB) complex method. The intensity of immunostaining of IMP3 was calculated in terms of mean area percent (MA %) and mean optical density (MOD) by Image J software.
Positive immunoreactivity of IMP3 was detected in normal salivary gland tissue (NSGT), as well as in benign and malignant SGTs. Weak cytoplasmic expression was detected in the ductal and myoepithelial cells of NSGT, while the acini were IMP3 negative. Moderate cytoplasmic expression was detected in the benign tumors. As for the malignant tumors, they showed strong IMP3 immunoreactivity. The pattern of immunostaining was predominantly cytoplasmic. Membranous reaction was detected in the mucus secreting cells of low grade mucoepidermoid carcinoma, clear myoepithelial cells in carcinoma ex pleomorphic adenoma and myoepithelial carcinoma, and clear cells in acinic cell carcinoma. Membranous reaction was also detected in the ductal cells of Ca ex PA in addition to the cytoplasmic reaction. Nuclear IMP3 immunoreactivity was observed in some cells in basal cell adenocarcinoma besides the cytoplasmic staining.
The intensity of IMP3 immunoexpression was compared between NSGT, benign and malignant tumors. The lowest MA% and MOD were detected in NSGT, while the highest MA% and MOD were detected in the malignant tumors with a statistically significant difference (p<0.001). Also, when comparing benign to malignant tumors, there was a statistically significant difference in MA% and MOD (p<0.001). As regards to malignant tumors, IMP3 immunoexpression was more intense in high grade tumors as compared to low grade ones. There was a statistically significant difference between them in the MA% and MOD (p<0.001).
It is concluded from the present study that IMP3 was highly expressed in malignant SGTs as compared to benign SGTs. Moreover, it may be an indicator of aggressiveness due to its stronger expression in high grade tumors.