الفهرس 
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Abstract
Malignant bone tumours are common group of malignancies in children, ranking the second pediatric malignancies according to last registries of Egyptian NCI.
Most cancer deaths occur due to metastatic spread. Ezrin is a membrane cytoskeletal linker protein which has been suggested to be an importantly involved molecule in metastasis. VEGF is an angiogenesis promoting factor. During the process of haematogenous metastasis, it plays a pivotal role through the promotion of new vessel formation.
A total of 53 cases were chosen from those presented to the department of pathology, faculty of medicine, El-Minia University Hospital and the Egyptian NCI. These cases included 30 cases of osteosarcoma, 20 cases of Ewing’s sarcoma, and 3 cases of primary conventional chondrosarcoma.
On studying the expression of Ezrin, significant association was found between Ezrin expression and histopathological tumour types (p=0.006), where positive Ezrin expression were mainly seen in ES (95%) followed by OS (76.7%), while all CHS cases were negative for Ezrin immunoreactivity.
The current study showed significant positive associations between Ezrin expression scores and both of tumour grade and stage in OS cases (p= 0.01, p=0.001 respectively), where high expression scores were seen mainly in high grade and advanced stage OS.
On studying the association of Ezrin subcellular localization in relation to tumour biological features in OS cases, no significant associations were found in relation to any of these variables. However, the combined cytoplasmic and membranous pattern was predominantly seen in high grade and advanced stage tumours compared to low grade and early stage tumours.
No significant difference was identified between primary osteosarcoma and their corresponding pulmonary metastasis regarding Ezrin expression, with high expression scores in all cases of primary as well as metastatic lesions.
In ES group, neither Ezrin expression score nor its subcellular localization was significantly associated with any of the clinicopathological features. However, 80% of cases showing combined membranous and cytoplasmic expression pattern were in advanced stage (stage IIB).
With respect to VEGF immuoreactivity, the VEGF expression rates were 100%, 95% and 80% for CHS, ES and OS respectively, with no significant association was found between VEGF expression and tumour histopathological types. Significant positive association was detected between VEGF and both of tumour grade and stage (p=0.01, p=0.03 respectively) in OS cases, where high expression scores were mainly seen in tumours of higher grade and advanced stage.
On studying the association of subcellular localization in relation to tumour biological features in OS cases, no significant association was found in relation to any variable, although most of high grade cases showed cytoplasmic expression and it was the predominant pattern of expression in all tumour stages including advanced cases.
No significant difference was noticed in VEGF expression between primary osteosarcoma cases and their corresponding pulmonary metastasis, with high expression scores were noticed in all cases for both locations (primary and metastasis).
Concerning ES cases, no significant associations could be detected between VEGF expression and all the available clinicopatholoical data. Similarly, in CHS cases, no significant associations could be seen between VEGF expression and all clinicopathological data.
Overall, the present study identified significant positive association between both markers (p= 0.003). Most tumours showing positive Ezrin expression, displayed VEGF immunoreactivity, this significant positive association was also maintained in OS and ES cases (p= 0.001; p= 0.03 respectively), but not in CHS cases.