|Year : 2018 | Volume
| Issue : 2 | Page : 80-83
Expression of stem cell marker CD44 in selected benign and malignant salivary gland tumors
Manal Abdulaziz Alsheddi1, Afnan Aljuaid2, Dalia Mohammed2
1 Department of Basic Sciences, College of Dentistry, Princess Nourah Bint Abdulrahman University, Riyadh, Saudi Arabia
2 The Contributors are General Practitioners, King Saud University, Riyadh, Saudi Arabia
|Date of Web Publication||14-Sep-2018|
Manal Abdulaziz Alsheddi
Department of Basic Sciences, College of Dentistry, Princess Nourah Bint Abdulrahman University, PO Box 230753, Riyadh 11321
Source of Support: None, Conflict of Interest: None
Background: Salivary gland (SG) tumors are among the unique neoplasms exhibiting complex histological features. The histogenesis remains unclear, and several pathways have been proposed. CD44 is a hyaluronic acid receptor that plays an essential role as an adhesion molecule for extracellular matrix components. The aim of the study is to investigate the expression of CD44 in selected SG tumors and determine its contribution to different biological behaviors of the tumors.
Materials and Methods: CD44 expression was examined in 31 tumors using immunohistochemistry. CD44 was expressed in neoplastic cells of all tumors.
Results: In pleomorphic adenoma, expression was more prominent in areas with ductal differentiation compared to myxoid areas. In all tumors, the proportion of tumor cells with positive staining ranged from 30% to 100%, except in adenoid cystic carcinoma, which expressed 10%–30% positive cells in two of the three samples analyzed. In conclusion, CD44 is expressed in epithelial neoplastic cells of pleomorphic adenoma, myoepithelioma, mucoepidermoid carcinoma, and adenoid cystic carcinoma. The relatively weak CD44 expression in plasmacytoid cells and myxoid areas of pleomorphic adenoma may indicate a more mature phenotype.
Conclusion: There was no differential staining of CD44 among selected tumors. Further studies with a larger sample size and proper documentation are required.
Keywords: CD44, Salivary gland tumor, salivary glands, stem cells
|How to cite this article:|
Alsheddi MA, Aljuaid A, Mohammed D. Expression of stem cell marker CD44 in selected benign and malignant salivary gland tumors. Saudi J Oral Sci 2018;5:80-3
|How to cite this URL:|
Alsheddi MA, Aljuaid A, Mohammed D. Expression of stem cell marker CD44 in selected benign and malignant salivary gland tumors. Saudi J Oral Sci [serial online] 2018 [cited 2019 Jan 21];5:80-3. Available from: http://www.saudijos.org/text.asp?2018/5/2/80/241165
| Introduction|| |
Salivary gland (SG) tumors are among the most unique neoplasms as they exhibit complex and overlapping histological features. They are broadly categorized into benign and malignant tumors. Malignant tumors are less common, comprising 3%–6% of all head and neck malignancies and 0.3% of all cancers.
Diagnosis of SG neoplasms presents a challenge for both the pathologist and clinician due to a range of diverse clinical and histopathologic features as well as tumor behavior and management options. The histogenesis of different SG neoplasms remains unclear, and several pathways have been proposed., A small group of neoplasm-initiating cells or cancer stem cells (CSC) have been implicated in the stages of tumor development. The CSC hypothesis states that the development of neoplasms is associated with normal stem cells and that a subset of cancer cells retaining stem cell properties may play a role in tumor initiation, progression, metastasis, and recurrence.
CD44 is a hyaluronic acid receptor that plays an essential role as an adhesion molecule for extracellular matrix components. It is thought to be involved in leukocyte activation, cell migration, wound healing, maintenance of cancer cell stemness, and the increased metastatic potential of tumors., It is one of the most investigated stem cell markers, and overexpression of CD44 is well documented in a large number of neoplasms., Animal studies have shown that CD44 is critical during glandular tissue morphogenesis, including SG development.
Our aim is to study the expression of CD44 in selected benign and malignant SG tumors to determine if this marker contributes to the different biological behaviors of the selected tumors.
| Materials and Methods|| |
All parts of this study were conducted in compliance with the “Ethical Principles for Medical Research Involving Human Subjects” as stated in the Helsinki Declaration. It was approved by the Committee of Ethics in Research of the College of Dentistry Research Center (IR0183).
The histopathology archive of the Histopathology Laboratory of College of Dentistry at XXX was retrospectively reviewed for selected tumors of SGs from January 1994 to December 2015. Tumors diagnosed as pleomorphic adenoma, myoepithelioma, mucoepidermoid carcinoma, and adenoid cystic carcinoma were selected for inclusion in the study.
All available hematoxylin and eosin (H and E) slides were re-examined to confirm the diagnosis and to select representative tissue blocks. Available data regarding age, gender, and anatomical location of the tumors were recorded. Thirty-one tumors were selected based on the availability and adequacy of tissues and are as follows: 17 pleomorphic adenomas, 8 mucoepidermoid carcinomas, 3 adenoid cystic carcinomas, and 3 myoepitheliomas.
The tissue sections were dewaxed and pretreated for 60 min at 95°C with cell conditioning solution 1 (CC1). The slides were incubated for 60 min at 37°C with a 1:100 dilution of an anti-CD44 antibody (Clone SP37, Ventana Medical Systems Inc., Tucson, Arizona). The immunoreactions were visualized using the ultraView Universal DAB (diaminobenzidine) Detection Kit in an automated autostainer (Ventana Roche, Benchmark XT). The immunoreactivity of the tumor tissues was evaluated semi-quantitatively using the Allred scoring system. The proportion of tumor cells with positive staining (PS) was scored from 0 to 5 with the following criteria: 0 (none), 1 (>0–1/100), 2 (>1/100–1/10), 3 (>1/10–1/3), 4 (>1/3–2/3), or 5 (>2/3-1). The intensity of the staining (IS) was scored as 0 (none), 1 (weak), 2 (intermediate), and 3 (strong). A total score was calculated as the sum of PS and IS (ranging from 0, 2-8). The Chi-square test was applied to analyze the statistical significance of the data when applicable. P < 0.05 was considered statistically significant.
| Results|| |
A total of 31 cases of SG tumors with available and adequate tissue blocks were analyzed and included 17 pleomorphic adenomas, 3 myoepitheliomas, 8 mucoepidermoid carcinomas, and 3 adenoid cystic carcinomas. The mean age, gender, and anatomic location are presented in [Table 1].
|Table 1: Distribution of age, gender, and anatomic location of the 31 salivary glands tumors|
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CD44 was expressed in neoplastic cells of all tumor types. In pleomorphic adenoma, the expression was more prominent in areas with ductal differentiation compared to myxoid areas. Focal plasmacytoid myoepithelial cells showed relatively weak expression [Figure 1]a, [Figure 1]b, [Figure 1]c. Myoepithelioma showed uniform expression in all tumor cells, while in mucoepidermoid carcinoma, expression was confined to dermal, mucous, and intermediate cells. Expression was also confined to myoepithelial cells in adenoid cystic carcinoma [Figure 1]d, [Figure 2]a and [Figure 2]b.
|Figure 1: Immunohistochemical staining of CD44 in pleomorphic adenoma (a) ductal differentiation, (b) myxoid area, (c) plasmacytoid cells, and (d) myoepithelioma (anti CD44, ×400)|
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|Figure 2: Immunohistochemical staining of CD44 in mucoepidermoid carcinoma (a) and adenoid cystic carcinoma (b) (anti-CD44, ×400)|
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In all tumors, the proportion of tumor cells with PS ranged from 30% to 100%, except in adenoid cystic carcinoma, which expressed 10%–30% positive cells in two of the three samples analyzed. This observed difference was not statistically significant. The majority of neoplastic cells in pleomorphic adenoma (64%), myoepithelioma (100%), and mucoepidermoid carcinoma (62%) showed a strong staining intensity, while 66.67% of adenoid cystic carcinoma exhibited an intermediate staining intensity [Table 2]. There were no significant differences among the groups in this study.
|Table 2: Expression of CD44 in 31 salivary gland tumors according to Allred scoring system|
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| Discussion|| |
The stem cell marker CD44 has been expressed in epithelial neoplastic cells of benign and malignant SG tumors with slight variability. The expression of CD44 has been investigated and reported in several SG tumors, such as pleomorphic adenoma, adenoid cystic carcinoma, and mucoepidermoid carcinoma.,,
Pleomorphic adenoma is the most common benign SG tumor, characterized by variable cytomorphologic and architectural patterns. The tumor has ductal, myoepithelial, and stromal components. There was strong expression of CD44 in areas with ductal differentiation compared to myxoid and plasmacytoid areas, which exhibited moderate intensity. Focal reactivity of plasmacytoid cells in pleomorphic adenoma was reported by Lanez et al. This differential expression of CD44 in different areas of the tumor suggests neoplastic cell maturity.
Myoepitheliomas are controversial and uncommon benign neoplasms composed of proliferative myoepithelial cells that lack ductal differentiation. Myoepithelioma was considered a variant of pleomorphic adenoma, but it is now classified as separate entity since 1991 according to the World Health Organization. Myoepithelial cells in all samples were uniformly and strongly reactive to CD44 except in focal myxoid areas, which were less reactive. To the best of our knowledge, the expression of CD44 in myoepithelioma has not been investigated previously. The uniform and strong immunoreactivity to CD44 may be attributed to the histogenesis of this tumor, which supports the hypothesis that the neoplastic cells in myoepithelioma are modified myoepithelial cells and are not fully differentiated.
Mucoepidermoid carcinoma is the most common malignant SG tumor. It is composed of three cell types in variable proportions, including epidermoid, mucous, and intermediate. According to different grading schemes, mucoepidermoid carcinoma is graded as low, intermediate, or high grade. CD44 was strongly expressed in all cell types of the tumor. Similar findings has been reported by several authors.,, The correlation between tumor grade and CD44 expression could not be tested due to the limited number of cases.
Adenoid cystic carcinoma is an uncommon malignant neoplasm characterized by an indolent and locally invasive growth pattern. Local recurrence and distant metastasis are common features of the tumor. CD44 was observed in the myoepithelial cell component of the tumors, with strong expression in one out of three tumors. This observation is in agreement with previous reports.,, It has been proposed that CD44 positive cells are key players in tumor morphogenesis through interaction with the extracellular matrix.
The current research has generated information about the expression of the stem cell marker CD44 in select benign and malignant SG tumors; however, these findings have to be carefully interpreted due to the small sample size of the study. Further study of CD44 expression and correlation with metastasis or recurrence could not be conducted due to the lack of proper documentation of clinical and pathological data.
| Conclusion|| |
The study has demonstrated that the stem cell marker CD44 is expressed in epithelial neoplastic cells of pleomorphic adenoma, myoepithelioma, mucoepidermoid carcinoma, and adenoid cystic carcinoma. The relatively weak CD44 expression in plasmacytoid cells and myxoid areas of pleomorphic adenoma suggests neoplastic maturity compared to areas with ductal differentiation. As there was no differential staining of CD44 among the selected tumor samples, it does not seem to pose diagnostic significance; however, the effect of small sample size should be appreciated. Further studies with a larger number of cases and proper documentation are required for analysis of the role of CD44 expression in this subset of tumors.
This research was partially supported by the College of Dentistry Research Center, King Saud University, Riyadh, KSA. The authors are grateful for this support.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2]
[Table 1], [Table 2]