A Review of Selected Factors of Salivary Gland Tumour Formation and Malignant Transformation

BubR1 and cyclin B1 immunoexpression in pleomorphic adenoma and polymorphous adenocarcinoma of minor salivary glands

The immunoexpression of BubR1 and cyclin B1 in pleomorphic adenoma (PA) and polymorphic adenocarcinoma (PAC) in minor salivary glands is poorly studied. Thus, a retrospective and observational study was performed to provide a better understanding of the role and immunopositivity patterns of these proteins in these lesions. Sixteen cases of PA and 16 cases of PAC were selected. Parenchyma cells were submitted to quantitative immunohistochemical analysis through the labeling index. Cytoplasmic immunoexpression of BubR1 was observed in neoplastic cells from all analyzed PA and PAC cases. All PA cases and 93.7% of PAC exhibited nuclear immunoexpression of BubR1. Higher cytoplasmic and nuclear immunoexpression of BubR1 was observed in PAC (p = 0.001 and p = 0.122, respectively). Cytoplasmic immunoexpression of cyclin B1 was observed in all cases of PA and PAC, with a higher labeling index in the latter (p < 0.001). There was a significant positive correlation between nuclear and cytoplasmic BubR1 immunoexpressions (p < 0.001) in PA and a significant negative correlation between BubR1 and cyclin B1 cytoplasmic immunoexpressions (p = 0.014) in PAC. The higher cytoplasmic and nuclear immunoexpression of BubR1 in PACs suggests the continuous maintenance of neoplastic cells in the cell cycle and migration. Higher immunoexpression of cyclin B1 supports this lesion's enhanced proliferative and migration ability.

Application of ultrasound in distinguishing the incipient microtumor from inherent lymph nodes of the parotid glands

BACKGROUND

Parotid microtumors (size ≤ 1 cm) pose a significant clinical challenge due to their malignant potential and risks associated with surgery. It is imperative to explore the diagnostic workflow that incorporates ultrasound (US) in order to make appropriate clinical decisions with minimal invasiveness.

METHODS

The patients receiving both US and ultrasound-guided fine needle aspiration (USFNA) for the parotid microtumors in a medical center were retrospectively recruited. The ultrasonic features, cytology of USFNA, and final surgical pathology were analyzed to differentiate the tumor origins and their malignant potential.

RESULTS

From August 2009 to March 2016, a total of 92 patients were enrolled in the study. The short axis, long-to-short axis ratio, and presence of an echogenic hilum were found to be significantly useful in distinguishing lymphoid tissue origin from salivary gland origin, which was confirmed by USFNA. An irregular border was predictive for malignant parotid microtumors from both origins. Intra-tumoral heterogeneity was also identified as a significant feature associated with malignant lymph nodes. USFNA was able to confirm all malignant lymph nodes, but it had a false negative rate of 8.5% in parotid microtumors of salivary gland origin. Based on the analysis of US and USFNA results, a diagnostic workflow for parotid microtumors was proposed.

CONCLUSION

US and USFNA can be helpful in classifying the origins of parotid microtumors. US-FNA carries the risk of producing false negative results specifically for microtumors originating from salivary glands, but not lymphoid tissue. The diagnostic workflow, which incorporates both US and USFNA, assists in determining the clinical decision for diagnosing and managing parotid microtumors.

Simultaneous Expression of PD-1 and PD-L1 in Peripheral and Central Immune Cells and Tumor Cells in the Benign and Malignant Salivary Gland Tumors Microenvironment

BACKGROUND

To investigate the differential expression of PD-1 and PD-L1 in salivary gland tumors (SGTs, malignant and benign subtypes) and determine their association with the clinicopathological characterization of the patients.

METHODS

The immunohistochemistry was used to examine PD-1 and PD-L1 expression in specimens from 83 patients with primary SGTs including salivary ductal carcinoma (SDC), adenoid cystic carcinoma (AdCC), acinic cell carcinoma (ACC), mucoepidermoid carcinoma (MEC), warthin's tumors (WT), poleomorphic adenoma (PA) and other subtypes.

RESULTS

The expression of PD-1 in peripheral and central immune cells (ICs) of MEC, and peripheral ICs of ACC was significantly higher than those with AdCC (P = 0.02, P = 0.02, P = 0.03, respectively). Interestingly, the expression of PD-1 was also observed in peripheral and central malignant tumor cells (TCs), particularly in SDC and ACC. Despite no significant difference in PD-L1 expression of TCs among malignant subtypes, the peripheral and central ICs of ACC and MEC were revealed to express PDL-1 significantly more than those with AdCC (P < 0.05). WTs were rich in PD-1/PD-L1 expressing ICs. However, the tumor microenvironment of PA generally had low levels of PD-1/PD-L1 expression. In general, the expression of PD-1 in peripheral and central TCs was found to be significantly higher in malignant tumors than in benign ones (P = 0.002 and P = 0.003, respectively).

CONCLUSION

The simultaneous presentation of PD-1 and PD-L1 in TCs and ICs of SGTs, their significant association with disease severity as well as the positive correlation between these immune checkpoints may suggest the therapeutic potential of anti-PD-1 and anti-PDL-1 combinational immunotherapy for SGTs.

Immunological and biological dissection of normal and tumoral salivary glands

Salivary glands naturally play central roles in oral immunity. The salivary glands microenvironment inevitable may be exposed to exogenous factors consequently triggering the initiation and formation of various malignant and benign tumors. Mesenchymal stem cells are recruited into salivary gland microenvironment, interact with tumor cells, and induce inhibitory cytokines as well as cells with immunosuppressive phenotypes such as myeloid-derived suppressor cells (MDSCs) and regulatory T cells (Tregs). The immune components and tumor immune responses in malignant and benign SGTs are still under investigation. Immune responses may directly play a limiting role in tumor growth and expansion, or may participate in formation of a rich milieu for tumor growth in cooperation with other cellular and regulatory molecules. Immune checkpoint molecules (e.g. PDLs, HLA-G and LAG3) are frequently expressed on tumor cells and/or tumor-infiltrating lymphocytes (TILs) in salivary gland microenvironment, and an increase in their expression is associated with T cell exhaustion, immune tolerance and tumor immune escape. Chemokines and chemokine receptors have influential roles on aggressive behaviors of SGTs, and thereby they could be candidate targets for cancer immunotherapy. To present a broad knowledge on salivary glands, this review first provides a brief description on immunological functions of normal salivary glands, and then describe the SGT's tumor microenvironment, by focusing on mesenchymal stem cells, immune cell subsets, immune checkpoint molecules, chemokines and chemokine receptors, and finally introduces immune checkpoint inhibitors as well as potential targets for cancer therapy.

Expression of Syndecan-1 and Cyclin D1 in Salivary Gland Tumors in Relation to Clinicopathological Parameters

Background

Salivary tumors have various morphological features and might share some histopathological findings. They are considered a problematic area in diagnosis due to complex clinicopathological features and different biological behavior.

Objective

To identify the pathological behavior of salivary tumors immunohistochemically.

Methodology

This retrospective study involved thirty formalin-fixed paraffin-embedded blocks of salivary gland tumors. These tumors were stained immunohistochemically with syndecan-1 and cyclin D1. Chi-Square test was used to relate immunoscoring, intracellular localization, intensity, and invasion to different salivary tumors. The correlation of these two markers was done by spearman's rho test. P-value <0.05 was considered statistically significant.

Results

The mean age of the patients was 48.69 ± 17.7. The parotid gland was the most commonly reported site in benign tumors, and regarding malignant tumors, maxilla was the most prevalent site. Syndecan-1 in benign tumors showed a predominate score 3, most widely detected in pleomorphic adenoma. Malignant salivary tumors showed 89.4% positive expression with a more frequent score 3, most commonly found in adenocystic carcinoma. Cyclin D1 expressed in all benign salivary tumors, with prominent diffuse mixed intracellular localization in pleomorphic adenoma. Malignant tumors revealed an expression of 94.7%. Moderate scoring with mixed intracellular localization was recorded in adenocystic carcinoma, followed by mucoepidermoid carcinoma. There was a significant correlation between the two markers in response to the distribution of immunostaining in different cell compartments.

Conclusion

Syndecan-1 and cyclin D1 showed a significant combined role in salivary tumor progression. Interestingly notable ductal-myoepithelial cells affect epithelial morphogenesis, and growth of pleomorphic adenoma was observed. Furthermore, basophilic cells of cribriform adenocystic carcinomas might control the aggressiveness and proliferation rate of these tumors.

Salivary gland tumours: an epidemiological review of non-neoplastic and neoplastic pathology

Salivary gland tumours (SGT) demonstrate geographical variation. The primary objective of this study was to determine the types, frequency, distribution, and demographics of non-neoplastic and neoplastic salivary gland pathology at Waikato Hospital, New Zealand (NZ) over a 10-year period. Following this we conducted a 10-year retrospective review of SGT epidemiology from international literature. In total 825 patients were identified, 31% (256/825) with non-neoplastic salivary gland pathology, 34% (284/825) with benign neoplastic pathology, 14% (118/825) with primary malignant lesions, 18% (146/825) with metastatic SGTs, and 3% (21/825) with lymphoma. Patients had a mean (range) age of 58 (3-102) years, were predominantly male (58%, 476/825), and NZ European (65%, 536/825). Tumours were most prevalent in the parotid gland (85%, 484/569), of which 44% (211/484) were malignant. Pleomorphic adenoma was the most common benign (71%, 203/284) and overall (36%, 203/569) tumour, while mucoepidermoid carcinoma (25%, 29/118) and squamous cell carcinoma (SCC) (73%, 106/146) were the most common primary malignant and metastatic SGTs, respectively. Our literature review identified 18 studies consisting of 33,933 patients, of whom 71% (24,013/33,933) had benign SGTs. Pleomorphic adenoma (68%, 16404/24013) and mucoepidermoid carcinoma (29%, 2826/9621) were the most common benign and malignant SGTs, respectively. Low numbers of non-neoplastic and metastatic SGTs were reported in the literature. This research provides a greater understanding of differences in their global distribution. Consistent with previous literature, pleomorphic adenoma and mucoepidermoid carcinoma were the most common benign and malignant SGTs. In NZ, we found high rates of malignant SCC to the parotid gland, consistent with the epidemiology of non-melanoma skin cancer in the country.

A Synopsis of Signaling Crosstalk of Pericytes and Endothelial Cells in Salivary Gland

The salivary gland (SG) microvasculature constitutes a dynamic cellular organization instrumental to preserving tissue stability and homeostasis. The interplay between pericytes (PCs) and endothelial cells (ECs) culminates as a key ingredient that coordinates the development, maturation, and integrity of vessel building blocks. PCs, as a variety of mesenchymal stem cells, enthrall in the field of regenerative medicine, supporting the notion of regeneration and repair. PC-EC interconnections are pivotal in the kinetic and intricate process of angiogenesis during both embryological and post-natal development. The disruption of this complex interlinkage corresponds to SG pathogenesis, including inflammation, autoimmune disorders (Sjögren’s syndrome), and tumorigenesis. Here, we provided a global portrayal of major signaling pathways between PCs and ECs that cooperate to enhance vascular steadiness through the synergistic interchange. Additionally, we delineated how the crosstalk among molecular networks affiliate to contribute to a malignant context. Additionally, within SG microarchitecture, telocytes and myoepithelial cells assemble a labyrinthine companionship, which together with PCs appear to synchronize the regenerative potential of parenchymal constituents. By underscoring the intricacy of signaling cascades within cellular latticework, this review sketched a perceptive basis for target-selective drugs to safeguard SG function.

Tracking of the biochemical changes upon pleomorphic adenoma progression using vibrational microspectroscopy

Head and neck tumors can be very challenging to treat because of the risk of problems or complications after surgery. Therefore, prompt and accurate diagnosis is extremely important to drive appropriate treatment decisions, which may reduce the chance of recurrence. This paper presents the original research exploring the feasibility of Fourier transform infrared (FT-IR) and Raman spectroscopy (RS) methods to investigate biochemical alterations upon the development of the pleomorphic adenoma. Principal component analysis (PCA) was used for a detailed assessment of the observed changes and to determine the spectroscopic basis for salivary gland neoplastic pathogenesis. It is implied that within the healthy margin, as opposed to the tumoral tissue, there are parts that differ significantly in lipid content. This observation shed new light on the crucial role of lipids in tissue physiology and tumorigenesis. Thus, a novel approach that eliminates the influence of lipids on the elucidation of biochemical changes is proposed. The performed analysis suggests that the highly heterogeneous healthy margin contains more unsaturated triacylglycerols, while the tumoral section is rich in proteins. The difference in protein content was also observed for these two tissue types, i.e. the healthy tissue possesses more proteins in the anti-parallel β-sheet conformation, whereas the tumoral tissue is dominated by proteins rich in unordered random coils. Furthermore, the pathogenic tissue shows a higher content of carbohydrates and reveals noticeable differences in nucleic acid content. Finally, FT-IR and Raman spectroscopy methods were proposed as very promising methods in the discrimination of tumoral and healthy tissues of the salivary gland.

Raman spectroscopy and surface-enhanced Raman spectroscopy (SERS) spectra of salivary glands carcinoma, tumor and healthy tissues and their homogenates analyzed by chemometry: Towards development of the novel tool for clinical diagnosis

In this study, two approaches to salivary glands studies are presented: Raman imaging (RI) of tissue cross-section and surface-enhanced Raman spectroscopy (SERS) of tissue homogenates prepared according to elaborated protocol. Collected and analyzed data demonstrate the significant potential of SERS combined with multivariate analysis for distinguishing carcinoma or tumor from the normal salivary gland tissues as a rapid, label-free tool in cancer detection in oncological diagnostics. Raman imaging allows a detailed analysis of the cell wall's chemical composition; thus, the compound's distribution can be semi-quantitatively analyzed, while SERS of tissue homogenates allow for detailed analysis of all moieties forming these tissues. In this sense, SERS is more sensitive and reliable to study any changes in the area of infected tissues. Principal component analysis (PCA), as an unsupervised pattern recognition method, was used to identify the differences in the SERS salivary glands homogenates. The partial least squares-discriminant analysis (PLS-DA), the supervised pattern classification technique, was also used to strengthen further the computed model based on the latent variables in the SERS spectra. Moreover, the chemometric quantification of obtained data was analyzed using principal component regression (PCR) multivariate calibration. The presented data prove that the PCA algorithm allows for 91% in seven following components and the determination between healthy and tumor salivary gland homogenates. The PCR and PLS-DA methods predict 90% and 95% of the variance between the studied groups (in 6 components and 4 factors, respectively). Moreover, according to calculated RMSEC (RMSEP), R2C (R2P) values and correlation accuracy (based on the ROC curve), the PLS-DA model fits better for the studied data. Thus, SERS methods combined with PLS-DA analysis can be used to differentiate healthy, neoplastic, and mixed tissues as a competitive tool in relation to the commonly used method of histopathological staining of tumor tissue.

Can the height of the parotid tumor be a predictor of malignancy?

Background

Accurate diagnosis of malignancy in the parotid gland before surgery is often challenging. Various clues should be used to increase the index of suspicion for malignancy. We hypothesized that malignant lesions of the parotid gland are located at the superior part of the gland compared to benign ones.

Methods

A total of 169 consecutive patients were included in this study whose medical records were retrospectively reviewed. Benign and malignant tumors were compared in size, height difference from five anatomical landmarks: hard palate, mastoid tip, earlobe, condylar head, and mandibular notch. The cutoff heights from significant landmarks (hard palate, condylar head) were estimated with ROC analysis and chi-square test.

Results

Twenty-nine patients (17.2%) were diagnosed with malignant and 140 patients (82.8%) as benign. The height differed significantly between benign and malignant tumors when the reference point was set for the hard palate (P=0.024) and the condylar head (P=0.049), with the cutoff height from reference points to be 22.5, 51.5 mm, respectively. Diagnostic values of parotid level difference presented higher sensitivity (75.9% for hard palate, 72.4% for condylar head vs. 47.8% for fine needle aspiration cytology) and lower false negative rate (24.1% for hard palate, 27.6% for condylar head vs. 52.2% for fine needle aspiration cytology) compared to fine needle aspiration cytology.

Conclusions

Malignant tumors of the parotid gland tend to locate at the superior part of the gland compared to benign tumors. Parotid tumors lying cephalad should raise an index of suspicion for malignancy. Height of the tumor in the parotid gland should be deliberately considered during the first encounter of the patient, which in turn could curate the next step in the diagnostic approach and treatment planning.

The Impact of Angiogenesis in the Most Common Salivary Gland Malignant Tumors

Salivary gland carcinomas (SGCs) represent a group of rare tumors, with complete surgical resection being the main treatment option. Therapeutic armory for cases of locally aggressive, recurrent, and/or metastatic SGCs, though, remains poor since they exhibit high rates of resistance to systematic therapy. Angiogenesis is considered one of the contemporary hallmarks of cancer and anti-angiogenic factors have already been approved for the treatment of several cancer types. This review aims to summarize, in a histotype-specific manner, the most current available data on the angiogenic factors implicated in SGC angiogenesis, in order to highlight the differences between the most common SGC histotypes and the factors that may have a potential role as therapeutic targets.

DNA base excision repair and nucleotide excision repair proteins in malignant salivary gland tumors

OBJECTIVE

To analyze the immunohistochemical expression of the base excision repair (BER) proteins apurinic/apyrimidinic endonuclease 1 (APE1) and X-ray repair cross-complementing protein 1 (XRCC1) and nucleotide excision repair (NER) protein xeroderma pigmentosum group F (XPF) in malignant salivary gland tumors (MSGTs).

DESIGN

Sixty-two cases of MSGTs were selected, including 14 acinic cell carcinomas (AcCC), 15 polymorphous adenocarcinomas (PAC), 16 adenoid cystic carcinomas (ACC), and 17 mucoepidermoid carcinomas (MEC). The specimens were submitted to quantitative immunohistochemical analysis.

RESULTS

All MSGTs exhibited nuclear or nucleo-cytoplasmic immunostaining of APE1, XRCC1 and XPF, with a high percentage of positive cells (median = 78.31, 70.48 and 75.46, respectively). XRCC1 expression was higher in PAC compared to MEC (p = 0.032). Nuclear APE1 immunostaining was significantly higher than nucleo-cytoplasmic expression in the selected MSGTs (p < 0.0001). APE1 expression was significantly associated with T1-T2 tumors in ACC (p = 0.006). Increased expression of XPF was associated with age older than 60 years in MEC (p = 0.015) and with ACC involving the minor salivary gland (p = 0.012), while a lower expression was found in AcCC and ACC patients treated by surgery combined with adjuvant therapy (p = 0.036 and p = 0.020, respectively). Low expression of XRCC1 in the nucleus (p = 0.028) and concomitant expression of this protein in the nucleus/cytoplasm were associated with a lower overall 5-year survival rate (p = 0.017).

CONCLUSIONS

This study showed that BER and NER proteins evaluated are highly expressed in the MSGTs studied, indicating mechanisms of genotoxic control in these tumors. In addition, the dysregulation of XRCC1 expression was a prognostic predictor in MSGTs analyzed.

Salivary gland neoplasms: A 10-year review of a major referral center in Ghana

OBJECTIVE

The aim of this study was to describe the clinicopathologic features of salivary gland tumors (SGTs) that were managed at a major referral center in Ghana.

STUDY DESIGN

This was a retrospective study of all histologically diagnosed and managed Ghanaian patients with SGTs during the period January 2008 to December 2017. Information collected included age, gender, affected gland, presenting symptom, treatment modality, histologic diagnosis, and complications. Descriptive summaries of variables were generated. The χ² test with Fisher's test was used to compare categorical variables with subsequent testing of association.

RESULTS

The study included 116 patients, with 49 males (42.2%) and 67 females (57.8%), representing a ratio of 1:1.4. There were 82 (70.7%) benign SGTs and 34 (29.3%) malignant SGTs. The most common benign SGT was pleomorphic adenoma, which accounted for 62.1% of all SGTs. Malignant SGTs occurred more in older people, and the occurrence of SGTs was significantly at a lower age in males compared with females.

CONCLUSIONS

Although the general pattern of SGTs did not seem to differ significantly in comparison with the findings of a review performed 10 years earlier, the findings of this study could inform hypotheses generation for future studies to explore the risk factors and associations peculiar to the Ghanaian environment.

Stromal and epithelial syndecan-1 expression in benign and malignant salivary gland tumors: which is more reflective of behavior?

INTRODUCTION

Salivary gland tumors are a diverse group of lesions, with various origins and extremely different behaviors, leading to a variety of outcomes for patients. Therefore, the need to discover novel markers with the ability to predict the behavior of benign and malignant salivary gland neoplasms is crucial. Syndecan-1 is a cell-surface protein with significant roles in various aspects of tumor function. Its expression in salivary gland neoplasms, especially their stromal component, has not been investigated.

OBJECTIVES

We aimed to assess the immunopositivity of syndecan-1 in epithelial and stromal components of salivary gland neoplasms and to compare it between benign and malignant subtypes in addition to evaluating its correlation with clinicopathologic parameters.

METHODS

133 salivary gland tumors were immunohistochemically stained with syndecan-1 and the intensity and percentage of this protein was determined, compared between the tumors and correlated with clinicopathologic factors.

RESULTS

Statistical analysis of lesions with a sufficient sample size showed significant differences in percentage and intensity between both epithelial and stromal components of all tumors (p<0.05). Pairwise-comparisons demonstrated significantly higher staining-percentage of epithelial cells (p=0.02) in Warthin's tumor compared to pleomorphic adenoma and adenoid cystic carcinoma. Similarly, significantly higher staining intensities and/or percentages was observed in mucoepidermoid carcinoma and adenoid cystic carcinoma compared to pleomorphic adenoma and Warthin's tumor (p<0.05). Of the clinicopathologic factors, there was only a significant negative correlation between stromal percentage of mucoepidermoid carcinoma and age and a significant difference between stromal intensity+percentage of adenoid cystic carcinoma and gender (p<0.05).

CONCLUSIONS

According to our findings we postulate that stromal syndecan-1 correlates with the behavior of salivary gland tumors, with malignant neoplasms demonstrating a higher expression, indicating a role for syndecan-1 in invasion and metastasis.