The literature shows that clinical staging is the main prognostic factor for SGMN
[3, 30, 31]. Our data are in agreement with this assessment. The present study observed patients in an advanced clinical stage (III/IV) with relation to loco-regional recurrence. In our study, clinical staging also correlated with DFS by Kaplan–Meier tests. The clinical stage was proved to be an independent prognostic factor in the studies of Bell et al.
 and Lima et al.
. Similar, the present study demonstrated that patients in an early clinical stage had a better prognosis.
CD44 is main receptor for hyaluronate. CD44, 80 to 95KDa transmembrane protein has a pivotal role in cell-extracellular matrix interaction
. Besides the extracellular interaction with HA, fibronectin, collagen types I and IV, serglycin and osteopontin
 CD44 forms a complexes with ERM (ezrin-radixin-moesin) to establish a link with actin cytoskeleton
The CD44 receptor is one of the most studied markers for stem cells and is overexpressed in a large number of solid neoplasms. Among the previous CD44 analyses in epithelial tumors, some investigators found relation between this protein and stem cells behavior, suggesting the CD44 as key marker of this cell population
. However, recently the role of CD44-expression in solid neoplasms as a tumour marker for stem cells is discussed and controversial.
The relation between CD44 and neoplasms presents the breast cancer as the most well studied neoplasm; an experimental assay demonstrates that tumors within CD44-positive cell population possess cancer stem-cell behavior (10). Similar to these results the cancer stem-cell behavior of CD44-positive cells has also demonstrated in head and neck squamous cell carcinomas
Further findings demonstrate that CD44 expression can be related to clinicopathological features and the expression of immunohistochemical markers of prognostic significance. In an immunohistochemistry breast invasive ductal carcinoma study Oliveira-Costa and collaborators
 demonstrated the relation between CD44 expression and HIF1-Alpha status and HER-2 expression influencing the patient prognosis
. Choi and collaborators
 observed an association between CD44 expression and tumour size studding colorectal adenocarcinoma. Notwithstanding, The patients outcome has also been influenced in oral squamous cells carcinoma, the CD44+ subpopulation was a independent factor of a poor prognosis
. Nevertheless, the effect of CD44 expression on malignant neoplasms still demonstrates conflicting results, some paper demonstrated that decreased CD44-expression could influence a worse prognosis for the patient
[20, 21] in endometrioid carcinoma the CD44-expression was observed and no association was found between the protein expression and clinicopathological features suggesting that CD44-expression predictive prognostic factor
Examining salivary glands was demonstrated that CD44v3 and v6 variants are widely expressed by myoepithelial and acinar cells, suggesting that these myoepithelial cells may play a critical role in normal salivary gland renewal and may play a role in the control of growth of salivary gland tumors considered to be derived from modified myoepithelial cells
. Franchi and colleagues
 reported an intense expression of CD44 and CD44v6 in pleomorphic adenomas. This expression was observed in tubular structures, solid areas and areas with myxoid matrix or chondroid matrix production. They also verified that malignant neoplastic cells in carcinoma ex-pleomorphic adenoma cases were positive for CD44. Our data provide an interesting find related between CD44-expression and adenoid cystic carcinoma, was observed an expression of CD44 in myoepithelial component, however, the ductal component presents no expression (Figure
1C). ACC has an indolent nature and predilection to late distant metastasis
. ACC shares histopathological features with PMLG. Thus transforming the diagnosis in a challenge to pathologists
 to decrease the diagnostic difficulty several markers were suggested, an example is the proliferation marker MCM2 suggested by Ghazy and collaborators (2011)
. Supported by our Immunohistochemical findings we also suggest that CD44 could be used to differentiate borderline cases. However, further studies with large number of cases are recommended to support the idea. Our data has also provided evidence for a significant association between CD44 expression and SGMN in major salivary glands. This relationship was also suggested by the increased amount of positive staining in major salivary glands tumors when compared with neoplasms from minor salivary glands. A hypothetical explanation for the differential expression of CD44 could be the variation in histological features between the salivary glands and/or embryological development via the epithelium-mesenchyme relationship.
The CD24 receptor is a heavily-glycosylated protein constructed of 27 amino acids attached to the cell membrane by a GPI-anchor
. It was described as b-cell marker, and its expression is associated with b-cell development
[24, 45]. CD24 is related to P-selectin, an adhesion receptor for platelets and activated endothelial cells
. The association between CD24 and P-selectin was confirmed due to the interaction of mammary cancer cells and P-selectin in activated platelets
. This correlation suggests that CD24 plays an important role in metastatic events in human cancers
CD24 is considered as a new marker for stem cells. This cell surface glycoprotein is grouped together with classical stem cells markers such as CD44, CD133 and CD117. In animal models, the expression of CD24 is observed in submandibular glands
[47–49], Naduri and colleagues
 observed positive staining for CD24 in the submandibular excretory duct. This expression suggests a correlation between CD24 expression and the development of branching epithelium. Our study has shown positive CD24 expression in 9 SGMN cases. On the other hand Ma and colleagues
 reported that metastatic adenoid cystic carcinoma cell lines lack CD24 expression. Our results, in conjunction with the results of Ma and colleagues
, indicate that CD24 expression is not well established in SGMN. Our analysis of the CD24-positive cells in SGMN showed an association between CD24 expression, T stage and clinical stage. Cases that expressed CD24 were positively associated TIII/TIV tumors and with cancer stages III / IV. These results may suggest that CD24 correlates with advanced-stage SGMN.
The present study found no correlations between CD24 expression (total, cytoplasmic or membranous) and overall survival. We have also found no correlations between CD24 expression (total, cytoplasmic or membranous) and disease free survival. Oliveira and colleagues
, studying oral squamous cell carcinoma, have also found no relationship between total CD24 expression and overall survival. However, the CD24-cytoplasmic expression showed a correlation with disease free survival and overall survival. Kristiansen and colleagues
 highlighted that several studies analyzed only CD24-membranous expression although CD24-cytoplasmatic expression is usually presented as a prognostic factor for human cancer.
Both CD44 and CD24 have been established as stem cell surface markers and have been tested in several groups of tissues and cancers
[8–13]. The CD44/CD24 immunophenotypes behavior shows great diversity in human cancers.
In lesions of invasive breast cancer, Mylona and colleagues
 showed a correlation between the CD44+/CD24- immunophenotype and negative lymph node metastasis and lower staged tumors. However, this result disagrees with the findings of Abraham and coworkers
 that suggested an association between the CD44+/CD24- immunophenotype and distant metastasis but not with the clinical outcome. In vitro findings suggest that breast cancer cells with lymphatic metastatic ability and expressing the CD44+/CD24- immunophenotype have clonogenic potential and a higher ability to survive and grow in unfavorable environments
. In human cases, however, Giatromanolaki and colleagues
 found that breast cancer patients that present with CD44-/CD24- cells had a worsened overall survival.
Our data suggest that the relationship between CD44 and CD24 may have important role on clinicopathologic features. The immunophenotype CD44+/CD24- was the most prevalent, appearing in 52,2% of salivary glands tumors. Except for the double negative phenotype (CD44-CD24-), all of the immunophenotypes had a prevalent number of cases involving the major salivary glands. This result may suggest a lower activity of stem cells in minor salivary glands neoplasms. This finding could have therapeutic implications. A lower stem cell activity could result in an improved response to therapies aimed at eradicating minor salivary gland tumors. These diverse results reflect the controversial biological characteristics described by Carrillo and coworkers
 in minor salivary gland neoplasms. Factors that may influence disease free survival rates are histological type, tumor grade and clinical stage
. However, clinical stage is the principal prognostic factor for predicting disease outcome
[1, 3, 30, 31]. Our findings are in accordance with this literature-derived data.
The present study shows that SGMN with CD44+/CD24+ profile may represents the tumors with most aggressive behavior and worst prognosis. CD44+/CD24+ profiles was associated with tumor size and lymph node metastasis. The majority of the CD44+/CD24+ cases (66,6%) were classified as T3/T4 and the rate of positive lymph node metastasis was higher than the expected (35.7%). Thus, the double positive (CD44+/CD24+) profile may be correlated with the more advanced tumors and rapid disease development. This aggressive cell behavior was also demonstrated in CD44+/CD24+ pancreatic cancer cells. Injection of CD44+/CD24+ cells into an animal model resulted in tumors a mere 3 weeks after injection. The same results were not achieved with CD44-/CD24- pancreatic cancer cells. These data demonstrate the tumorigenic potential of pancreatic cancer cells bearing the CD44+/CD24+ immunophenotype
. This phenomenon was also observed in the study conducted by Huang and coworkers
, where CD44+/CD24+ pancreatic cancer cells showed an exacerbated tumorigenic potential. Because stem cells from salivary gland tissue and pancreatic tissue have similar capacities for proliferation and differentiation, due to their similar aggressive capacity, we can assume that the cancer stem cell from both tissues also has similar abilities