| BackgroundPleomorphic adenoma, also known as mixed tumor, is the most common parotid gland benign tumor. It comprises 60%-70% of all parotid gland neoplasms. Because of its incomplete peplos, it has a malignant potentiality after multiple recurrences. Thus, complete detection of early stages of a tumor of the parotid gland is extremely important in terms of prognosis after surgery.Surgical resection methods include simple tumor enucleation, complete superficial parotidectomy and total parotidectomy, partial superficial parotidectomy. Simple enucleation of pleomorphic adenoma does not remove peplos, in spite of fewer complications, it has a high recurrence rate. Complete superficial parotidectomy is the standard surgical way for treating pleomorphic adenoma currently and the recurrence rate less then 0.3%～4.0%. However, this surgical approach with a high incidence of facial contour disfigurement and transient facial nerve dysfunction. Nowadays, with the introduction of functional surgery concept, partial superficial parotidectomy is more and more popular. Compared with total parotidectomy, the partial superficial parotidectomy is only involved with the rare branch of the facial nerve. And then this surgical resection method is associated with a lower incidence of transient facial nerve dysfunction, facial contour disfigurement.In view of many advantages of the partial superficial parotidectomy, it has been used widely. However, there is not agreement in the medical literature confirming the exact margin of parotid tissue to be resected to avoid recurrence. Currently, many methods have been used for assessing the exact margin of parotid tissue to be resected, such as imaging techniques, naked eye evaluation and intraoperative frozen section. Diagnostic imaging techniques for pleomorphic adenoma allow exact information about the dimension, shape, internal echo, adjacent and character of this kind tumor. However, the imaging techniques are not sensitive for diagnosis of pseudopodia and the satellite lesions. The naked eye evaluation is subjective and not for precise evaluation. Despite intraoperative frozen section is considered to be the most reliable method to confirm the exact margin of parotid tissue to be resected, it is not accurate when there are pseudopodia and the satellite lesions. To avoid over-treatment and cure pleomorphic adenoma completely, it has very important research value and clinical significance to explore the exact margin of parotid tissue to be resected.There are often kinetic changes of the protein in the development process of various diseases. In the different stages of tumor, even the early stage without any clinical symptom, the proteins have changed. These proteins which changed in the early stage can develop into the indicators to judge the exact margin of parotid tissue to be resected to avoid recurrence. Therefore, it has become a hot topic to look for the effective molecular indicators to help to determine the safe surgical margin. Ki-67 is a cell proliferative activity associated antigen. Several studies have found that the expression level of Ki-67 was significantly lower in the parotid pleomorphic adenoma than adjacent tumor tissues(1.0 cm from the tumor), and considered that this protein could be as the safe excision margin index of the partial superficial parotidectomy. Nevertheless, its reliability and sensitivity have not yet been confirmed.Water channelaquaporin (AQP) is a class of cross-membrane proteins which can mediate the free water to passive transport rapidly, and now 13 kinds of AQP have been found. With the deepening of the study, AQP1 and AQP5 were found that it not only can mediate the free water and ion transport, but aso is very important impact for gas exchange, tumor angiogenesis and cell migration. Nowadays, there is little study about the expression of AQP in salivary gland tumors and surrounding tissue. In order to clarify the expression and distribution of AQP1 and AQP5 in the pleomorphic adenoma and peritumoral tissue, in this study, we detected the expression of AQP1, AQP5 level to study the possible roles and significances of them as the safe excision margin indicators of partial superficial parotidectomy.ObjectsTo study the feasibility of AQP1, AQP5 as the safe excision margin of partial superficial parotidectomy, and to explore whether they were more sensitive as the the safe excision margin indicators comparing with Ki-67.MethodsReal-time PCR was used to detect the expression level of AQP1, AQP5, Ki-67 mRNA in primary pleomorphic adenoma(A group), adjacent tumor tissues(B group: 0.5 cm from the tumor; C group:1.0 cm from the tumor; D group:1.5 cm from the tumor and E group:2.0cm from the tumor). Immunohistochemistry was applied to detect the expression of AQP1, AQP5, Ki-67 protein in the different groups above mentioned.ResultAs shown in the RT-PCR and immunohistochemistry, AQP1 and AQP5 existed in each group and the expression level of them were the highest in pleomorphic adenoma tissue. In addition, the level of AQP1 and AQP5 progressively increased with the distance from the tumor. The differences of group A, group B and group C had no statistical significance (P>0.05), that is to say the expression of AQP1 and AQP5 had no significant difference between pleomorphic adenoma tissue and adjacent tumor tissues (0.5 cm from the tumor and 1.0 cm from the tumor). Group A, group B, group C were compared with group D respectively, there were statistical significance (P<0.05), that is to say the expression of AQP1 and AQP5 had significant difference between adjacent tumor tissues 1.0 cm from the tumor and 1.5 cm from the tumor). The differences of group D and group E had no statistical significance (P>0.05), that is to say the expression of AQP-1 and AQP5 had no significant difference between adjacent tumor tissues 1.5 cm from the tumor and normal salivary gland tissue. Ki-67 expressed in each group, and the expression level was the highest in pleomorphic adenoma tissue. In addition, the expression of Ki-67 progressively increased with the distance from the tumor. The differences of group A and group B had no statistical significance P>0.05), that is to say the expression of Ki-67 had no significant difference between pleomorphic adenoma tissue and adjacent tumor tissues (0.5 cm from the tumor). Group A and group B were compared with group C, there were statistical significance (P<0.05), that is to say the expression of Ki-67 had significant difference between adjacent tumor tissues 0.5 cm from the tumor and 1.0 cm from the tumor. Group C was compared with group D and E, there was no statistical significance (P>0.05), that is to say the expression of this protein had no significant difference in adjacent tumor tissues 1.0,1.5 cm and 2.0 cm from the tumor.Conclusion1. AQP1 and AQP5 play important roles in the devolpment of pleomorphic adenoma.2. AQP1 and AQP5 could be the safe index to determine the surgical margin of pleomorphic adenoma.3. AQP1 and AQP5 have higher sentivity than Ki-67 as safe index to determine surgical margin. |
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