الفهرس 
IntroductionOnly 14 pages are availabe for public view
 |  | from | 101 |  |  |
| | | from | 101 | | |
Abstract
Cholesteatoma is a non-neoplastic lesion of the temporal bone that has the ability to expand gradually and cause complications by bone erosion of the surrounding structures. Since it was first prescribed in the nineteenth century, its pathogenesis and mechanism of bone resorption remain controversial (Olszewska et al., 2004). Both molecular and cellular events master its activity (Albino et al., 1998). In our thesis, we conducted a prospective quantitative immunochemical study of some factors related to the bone resorption activity of human acquired cholesteatoma including Ki-67, cytokeratin 13 (CK13), cytokeratin 17 (CK17) and basic fibroblast growth factor (b-FGF). The study group consisted of 19 patients with fresh acquired cholesteatoma operated in a tertiary referral center during the period from August 2014 ~ May 2016. Control tissues were collected from the bony canal skin of the same patients (n=8). Congenital and recurrent cases were excluded. Formalin fixed paraffin embedded tissues were made and kept for further immunostaining. The universal immunoperoxidase polymer technique of immunostaining was conducted using mouse monoclonal primary antibodies for CK13, CK17 and Ki-67 and rabbit polyclonal antibody for b-FGF. All the procedure was performed in a humidified chamber at room temperature. The study group was categorized into two subgroups according to the degree of invasiveness of cholesteatoma based upon a newly developed scoring system for bone erosion by counting the number of eroded bones seen radiologically and confirmed intraoperatively. According to this scoring, we had non-invasive group (score 0~3 & n=9) and invasive group (score ≥4 & n=10). Cholesteatoma tissues were compared to skin and the invasive group was compared to the non-invasive one regarding the expression of 4 studied factors. In addition, correlation between the expression of these factors and the grading score for bone erosion was calculated. Evaluation of tissue samples was done by two independent observers; pathologist and the researcher.
For Ki-67, a highly significant difference was found between cholesteatoma and skin (37.44% ±1.9 versus 20.96% ±1.2, P <0.001). In addition, significant difference was also found between the invasive group and non-invasive group of cholesteatoma (41.27% ± 2.13 versus 33.2% ± 2.6, P = 0.029). Finally, a moderate positive correlation was found between Ki-67 expression and the grading score for bone erosion (r = 0.547, P = 0.015).
Regarding CK17, we found a highly significant difference in its mean expression between cholesteatoma and the meatal skin (71.71% ± 2.45 versus 34.4% ± 8.37,P<0.001). The expression of CK17 was significantly increased in invasive cholesteatoma compared with the non-invasive group (76.57% ± 2.7 versus 66.32% ± 3.4, P = 0.033). Furthermore, a moderately significant positive correlation was seen between CK17 expression and the grade of bone erosion (r = 0.588, P = 0.008). This means that both Ki-67 and CK17 were overexpressed in cholesteatoma, and the expression was activated in the invasive cholesteatoma. For CK13, no significant difference was found between cholesteatoma and the meatal skin [49.5% (17.6) versus 46.7 % (11.1) respectively, P = 0.750] and no difference between invasive and non-invasive groups [48.25 (10) versus 49 (12), P > 0.05]. Regarding b-FGF, a highly significant difference was identified between cholesteatoma and skin tissues (58.53% ± 3.6 in cholesteatoma versus 40.6% ± 3.5 in skin; P = 0.005) but no significant difference between invasive and non-invasive group (61.13% ± 3.2 in invasive group versus 55.64% ± 6.9 in non-invasive group, P = 0.471). In our study, we provided a supporting evidence that the proliferative capacity of cholesteatoma as determined by Ki-67 immunostaining significantly correlated with its aggressive clinical behavior. In addition, we emphasized the role of CK17, a potential marker for oral malignancy in the pathogenesis as well as in bone destruction in cholesteatoma. Although cholesteatoma is a non-neoplastic lesion, it attains many characters similar to neoplasms like invasion, migration, proliferation and recidivism (Desloge et al., 1997). It can behave like a locally malignant neoplasm; however, it is non-neoplastic (Sayed, 2003).
Both Ki-67 and CK17 can be used to predict cholesteatoma behavior and hence we can plan the proper management which may necessitate early intervention to prevent complications.
In conclusion, we suggested a newly discovered positive role for CK17 in the pathogenesis of acquired cholesteatoma and its ability to destroy bony structures as well. Second, we added supporting evidence that Ki-67 could be considered as a reliable proliferative marker and predictor for cholesteatoma aggressiveness. Finally, we specifically determined the expression pattern of basic-FGF in cholesteatoma keratinocytes and emphasized its role in the pathogenesis of acquired cholesteatoma. This knowledge can be used for prediction of cholesteatoma behavior and also pave the way for future non-surgical management of acquired cholesteatoma.