Salivary gland pathologies: evolution in classification and association with unique genetic alterations

Heterogeneity in benign and malignant salivary gland tumors

Advanced proteomics tools have identified the role of proteins in cancer biology, highlighting the importance of these molecules for biomarker discovery and providing valuable insights into cancer diagnosis, prognosis, and targeted therapy. Proteome analysis of tissue using high-throughput proteomics techniques has identified proteins associated with recurrence and malignant transformation in benign tumors, and protein profiling of fine needle aspiration has revealed potential biomarkers for distinguishing malignant salivary gland tumors from benign ones. In addition, proteomics studies have identified distinct protein expression patterns in mesenchymal stem cells derived from malignant salivary gland tumors, suggesting a potential role for proteins in adverse behavior and/or targeted therapy. To provide a comprehensive knowledge of salivary gland tumors, this review will first provide a brief description of the molecular and cellular alterations in common benign and malignant salivary gland tumors and then describe the proteomics studies by concentration on different biological sources including serum/plasma, saliva, tumor tissues and related derivatives (e.g. mesenchymal stem cells, tumor cells, tumor established cell lines, and fine needle aspiration), and introduce potential targets for diagnosis, prognosis, and cancer therapy.

Clinical trials for patients with salivary gland cancers: A systematic review of worldwide registers and an evaluation of current challenges

BACKGROUND

Clinical trials (CT) are crucial for generating scientific evidence and improving clinical outcomes, but they can be challenging in the context of rare cancers. Salivary gland cancers (SGC) are rare and heterogeneous tumors, without standard-of-care approved systemic therapies. We analyzed completed and ongoing CTs to assess the current state of clinical research activity in the field.

METHODS

ClinicalTrials.gov, WHO-ICTRP, HealthCanadaCT were searched for antineoplastic pharmacological and interventional CT involving patients with SGC from the trials database creation until August 6th, 2024. CT characteristics and status were collected.

RESULTS

134 clinical trials met inclusion criteria. Of these, 78 % were sponsored by non-industry entities. 49 % were conducted at only one site, and 61 % at up to five centers. Only 25 trials (19 %) were multinational, being 15 industry-sponsored, a significantly higher proportion compared to non-industry-sponsored trials(p < 0.01). 16 % CTs were umbrella or basket, and 6 % were randomized, again predominantly industry-sponsored(p < 0.01). Regarding SGC-specific trials, 32 % were open to all patients with SGC, regardless of specific histology. Patients with adenoid cystic, salivary duct, and mucoepidermoid carcinoma had access to 92 %, 66 % and 62 % of trials, respectively. 88 % CT targeted palliative setting, and 38 % incorporated predictive biomarkers. Tyrosine kinase inhibitors were the most studied therapy(26 %), followed by immunotherapy(15 %), chemotherapy and antibody-drug conjugate(12 % each) and androgen-blockade(8 %), among others.

CONCLUSION

Clinical research for patients with SGC relies mainly in non-industry organisations, most of them limited to run trials in one to five sites, in a single country. Further collaboration between investigators is needed, as well as reconsidering inclusion criteria and trial designs.

Dual PD-1 and CTLA4 Immune Checkpoint Blockade and Hypofractionated Radiation in Patients With Advanced Salivary Gland Cancers

BACKGROUND

No standard systemic therapy exists for recurrent/metastatic salivary gland cancer (R/M SGC). We explored the safety and activity of nivolumab and ipilimumab with palliative hypofractionated radiation (XRT) in this population.

METHODS

This Phase I/II Trial enrolled R/M SGCs with evidence of progression, ECOG 0-1, no prior anti-PD-1 or CTLA4 therapy, measurable disease excluding the XRT site. Nivolumab 3 mg/kg iv Q2 weeks × 12 doses followed by 480 mg iv Q4 weeks × 8 doses and ipilimumab 1 mg/kg iv Q6 weeks × 4 doses was given. Twenty four gray XRT was given over three fractions, 2 weeks after the first dose of nivolumab. The primary endpoint was safety; secondary endpoints included RECIST 1.1 response (non-radiated lesions), progression free, and overall survival.

RESULTS

Between April 2019 and May 2022, 20 pts. were enrolled, the median age was 58 (range 27-77 years), 10 (50%) were male, and 12 (60%) had ECOG 0. Five (20%) Grade 3 AEs were observed in three pts.; no Grade 4 or 5 toxicities were observed. Among 19 response-evaluable patients, RECIST 1.1 PRs were observed in 4 (21%), in 2 pts. with salivary duct, 1 acinic cell, and 1 adenoid cystic, SD in 6 (31.5%) and PD in 9 (47.5%). With a median follow-up of 16 months, median OS was 25 months (95% CI: [18.7, 31]) and median PFS was 7.3 months (95% CI [2.5, 18.7]).

CONCLUSION

Nivolumab/ipilimumab and palliative XRT result in low rates of severe toxicities and modest response rates for SGC; further work is necessary to explore predictors for response.

Ultrasound-based deep learning to differentiate salivary gland tumors

OBJECTIVE

Accurate preoperative diagnosis is essential for selecting appropriate surgical interventions. This study aims to develop a deep learning model based on ultrasound (US) imaging to accurately differentiate between benign and malignant salivary gland tumors (SGTs).

STUDY DESIGN

A retrospective study was conducted on 315 patients who had preoperative US examinations and pathologically confirmed SGTs following surgical resection at our department (2020-2024). We included all three major salivary glands in our analysis, addressing class imbalance issues and expanding the scope of our study. US images were processed using several convolutional neural networks, including Inception v3, ResNet101d, EfficientNet, DenseNet, Vision Transformer, and ResNet50d. The ResNet50d model was fine-tuned using Focal Loss to further address class imbalance. The model's performance was compared with sonographers' diagnoses.

RESULTS

DeepSGT effectively identified critical regions within US images, achieving great diagnostic performance with an accuracy of 91.1%, sensitivity of 92.9%, specificity of 89.2%, and an area under the curve (AUC) of 0.94. This performance significantly exceeded that of sonographers, who had an accuracy of 80% and an AUC of 0.73.

CONCLUSIONS

The DeepSGT model demonstrates superior diagnostic capabilities over traditional methods in distinguishing benign from malignant SGTs, offering a valuable tool for clinical decision-making.

The Number of Positive Lymph Nodes Instead of Extranodal Extension and Nodal Diameter is an Independent Predictor of Survival and Treatment Outcome of High-Grade Parotid Gland Carcinoma

BACKGROUND

There is emerging evidence that current 8th edition of the American Joint Committee staging system is not sensitive enough to predict parotid gland carcinoma (PGC) survival outcomes.

PURPOSE

The present study aimed to analyze pathological nodal factors related to survival and treatment outcomes in a cohort of patients surgically treated with PGC.

STUDY DESIGN, SETTING, SAMPLE

We performed a retrospective cohort study of consecutive patients surgically treated with PGC at the authors' institution from January 1993 to December 2018. The inclusion criteria were as follows: confirmed high-grade parotid gland malignancy on histopathology first surgical treatment of the parotid cancer with neck dissection with curative intent at the study clinic; and sufficient data for review. The exclusion criteria were previous treatment in another institution, low-grade carcinomas, cases where neck dissection was not performed, incurable local disease and distant metastases at the time of first diagnosis, and patients lost to follow-up.

PREDICTOR VARIABLE

Predictor variable comprised pathological nodal factors grouped as the number of cervical node metastases, extranodal extension (ENE), largest diameter of nodal metastasis, and involvement of parotid lymph nodes.

MAIN OUTCOME VARIABLES

Outcomes evaluated were overall survival (OS), disease-specific survival (DSS), recurrence-free survival (RFS), locoregional recurrence-free survival, and distant metastasis-free survival (DMFS). OS was calculated from the day of biopsy or definitive surgery to the last known hospital follow-up date or the date of death found in the hospital records or social security data. DSS was calculated from the day of biopsy or definitive surgery until the last known follow-up or death from PGC reported in the patient record. Patients who died from causes other than the disease being studied are not counted in this measurement. Treatment outcome was evaluated through the occurrence of locoregional relapse of the disease or development of distant metastases. RFS was defined as the time from the date of biopsy or definitive surgery to the date of locoregional recurrence free survivalor DMFS reported in the patient record.

COVARIATES

Covariates were composed of a set of heterogeneous variables grouped into the following categories: demographic, pathologic, and clinical.

ANALYSES

Unadjusted and adjusted hazard ratios for each variable were calculated with univariate and multivariable Cox regression. The tatistical significance was defined at a P value of < .05.

RESULTS

The cohort of 112 patients included 62 males (55%) and 50 (45%) females. The mean age of the patients was 60.52 ± 15.22 years. The median follow-up time was 59 months (3-221 months). Adenoid cystic carcinoma was the most common tumor type with the incidence of 45%. Cumulative OS for the 5-and 10-year follow-up period was 75 and 61%, respectively. Locoregional recurrences occurred with 27 patients (24%), distant metastases occurred with 25 patients (22%), and both were diagnosed with 5 patients (6%). The number of metastatic nodes was the most important nodal prognostic factor related to OS (P = .02; HR = 2.67; CI = 0.03-6.35), DSS (P = .011; HR = 2.55; CI = .61-6.83), and DMFS (P = .005; HR = 2.85; CI = 0.12-4.76). The presence of pathological parotid nodes was associated with poorer RFS (P = .015; HR = 3.45; CI = 0.25-6.02).

CONCLUSION AND RELEVANCE

The number of metastatic lymph nodes, instead of ENE and largest nodal diameter, was the contributing factor associated with survival and treatment outcomes of surgically treated patients with high-grade PGC. Since the main function of staging system is to predict outcomes, the significance of ENE and nodal dimension in salivary gland cancer staging system requires further clarification. An important finding in the present study was that the presence of positive parotid lymph nodes was associated to locoregional treatment failure.

Clinical and Morphological Aspects of Aggressive Salivary Gland Mixed Tumors: A Narrative Review

Salivary gland tumors are a rare and heterogeneous group of neoplasms of the head and neck region. The mixed category of these tumors include the following entities: pleomorphic adenoma (PA), carcinoma ex pleomorphic adenoma (CEPA), salivary carcinosarcoma (CS), and metastasizing PA (MPA). The most common benign tumor of the salivary glands is PA. Metastasis and malignant degeneration have been reported in cases of PA of a salivary gland origin. Judging by their behavior, MPA, CEPA, and CS can be considered aggressive tumors. Invasive CEPA has been identified in the parotid gland more frequently. MPA and CS cases reported in the current literature are rare. In this paper, we present, narratively, the clinico-morphological features of this group of mixed tumors.

Prognostic factors for development of distant metastases in surgically treated high-grade salivary gland carcinomas: results of retrospective single center study with 213 patients

PURPOSE

Distant metastases (DM) are the primary cause of treatment failure and death of patients with salivary gland carcinomas (SGC). The purpose of present study was to evaluate factors predictive on DM development in a cohort of patients with high-grade salivary gland carcinomas.

METHODS

This was a retrospective cohort study of consecutive patients surgically treated with curative intention at the authors' institution from January 1993 to December 2018. Outcomes evaluated were overall survival (OS), disease specific survival (DSS), recurrence free survival (RFS), locoregional recurrence free survival (LRFS) and distant metastasis free survival (DMFS).

RESULTS

A total of 213 patients, 117 males (55%) and 96 females (45%), were included in the study. Parotid gland malignancies accounted for 56% of all cases. Adenoid cystic carcinoma (119 cases; 56%) was the most common tumor type. Cumulative OS for the 5-and 10-year follow-up period was 80% and 58% respectively. DM occurred with 75 patients (35%). The most common locations for DM were lung (55 cases; 73%) and liver (12 cases; 16%). Pathological nodal status, particularly the number of metastatic nodes, was the independent prognostic factor for OS, DSS, RFS and DMFS.

CONCLUSION

Number of metastatic lymph nodes, instead of extranodal extension and largest nodal diameter, was the contributing factor related to DMFS. Since the main function of staging system is to predict outcomes, the significance of extranodal extension and nodal dimension in salivary gland cancer staging system requires further clarification. The elective neck dissection could be considered therapeutic approach for high-grade SGC since occult metastases were detected in 33% of cases.

The efficacy of clinicopathological and imaging features in differentiating benign from malignant parotid micro- and minitumors: a retrospective analysis

OBJECTIVE

To compare clinicopathological and imaging features of micro- and minitumors of the parotid gland and provide a reference for preoperative prediction of benign vs malignant status.

STUDY DESIGN

Patients with parotid gland tumors treated surgically were selected. Relevant clinicopathological and imaging data were collected for patients with maximum tumor diameters ≤20 mm on preoperative computed tomography (CT). The lesions were divided into 2 groups, microtumors and minitumors, based on maximum tumor diameter. CT imaging features of benign and malignant tumors were compared through binary logistic regression analysis.

RESULTS

Microtumors and minitumors were categorized by maximum diameters <10 mm (n = 74) and 10-20 mm (n = 611), respectively. Benign and malignant minitumors exhibited significant differences in boundary, tumor density, margin morphology, spiculation margin, and CT values in the plain and arterial phase (P ≤ .027), resembling those found in typical malignant parotid gland tumors. However, no significant differences were observed between benign and malignant microtumors. Logistic regression analysis identified boundary, margin morphology, and spiculation margin as independent predictors of malignancy. The prediction model excelled in identifying benign lesions but was less successful in identifying malignancies.

CONCLUSION

Parotid gland minitumors had imaging features similar to typical larger malignant tumors. Active exclusion of the malignant risk and early surgical treatment is recommended for these tumors.

Metastatic cutaneous squamous cell carcinoma accounts for nearly all squamous cell carcinomas of the parotid gland

Primary squamous cell carcinoma of the parotid gland (pSCCP) has long been recognized as a separate entity and is included in the WHO classifications of salivary gland tumors. However, it is widely accepted among head and neck pathologists that pSCCP is exceptionally rare. Yet, there are many publications describing series of pSCCP and data from SEER and other cancer register databases indicate erroneously an increasing incidence of pSCCP. Importantly, pSCCP and metastatic (secondary) squamous cell carcinoma to the parotid gland (mSCCP) have nearly identical histological features, and the diagnosis of pSCCP should only be made after the exclusion of mSCCP. Moreover, all of the histological diagnostic criteria proposed to be in favor of pSCCP (such as, for example, dysplasia of ductal epithelium) can be encountered in unequivocal mSCCP, thereby representing secondary growth along preexistent ducts. Squamous cell differentiation has also been reported in rare genetically defined primary parotid carcinomas, either as unequivocal histological squamous features (e.g., NUT carcinoma, mucoepidermoid carcinoma), by immunohistochemistry (e.g., in NUT carcinoma, adamantinoma-like Ewing sarcoma, basal-type salivary duct carcinoma, mucoepidermoid carcinoma), or a combination of both. Another major issue in this context is that the International Classification of Diseases (ICD) coding system does not distinguish between primary or metastatic disease, resulting in a large number of patients with mSCCP being misclassified as pSCCP. Immunohistochemistry and new molecular biomarkers have significantly improved the accuracy of the diagnosis of many salivary gland neoplasms, but until recently there were no biomarkers that can accurately distinguish between mSCCP and pSCCP. However, recent genomic profiling studies have unequivocally demonstrated that almost all SCCP analyzed to date have an ultraviolet light (UV)-induced mutational signature typical of mSCCP of skin origin. Thus, mutational signature analysis can be a very useful tool in determining the cutaneous origin of these tumors. Additional molecular studies may shed new light on this old diagnostic and clinical problem. This review presents a critical view of head and neck experts on this topic.

Current landscape and future trends in salivary gland oncology research-a bibliometric evaluation

Background

The salivary glands are susceptible to both endogenous and exogenous influences, potentially resulting in the development of oncology. With the wide application of various technologies, research in this area has experienced rapid growth. Therefore, researchers must identify and characterize the current research hot topics to grasp the forefront of developments in the dynamic field of salivary gland oncology. The objective of this study was to thoroughly assess the current status and identify potential future research directions in salivary gland oncology.

Methods

The relevant salivary gland oncology dataset was obtained from the Web of Science Core Collection (WOSCC) database. Subsequently, VoSviewer and CiteSpace were employed for further evaluation.

Results

A total of 9,695 manuscripts were extracted and downloaded from the WOSCC database. Our findings revealed a substantial surge in research volume over the past 12 years. The researchers' analysis revealed that Abbas Agami showed unparalleled dedication, with over 180 publications, and that RH Spiro had the highest cocitation count, confirming its status as a key figure in the field. The detection of bursts in secretory carcinoma and the integration of artificial intelligence in salivary oncology have attracted increasing interest. Notably, there is a discernible trend towards increased research engagement in the study of salivary gland malignancies.

Conclusions

This study not only evaluated the current research landscape in salivary gland oncology but also anticipates future trends. These insights could contribute to the advancement of knowledge and policymaking in salivary gland oncology.

Current Developments in Diagnosis of Salivary Gland Tumors: From Structure to Artificial Intelligence

Salivary glands tumors are uncommon neoplasms with variable incidence, heterogenous histologies and unpredictable biological behaviour. Most tumors are located in the parotid gland. Benign salivary tumors represent 54-79% of cases and pleomorphic adenoma is frequently diagnosed in this group. Salivary glands malignant tumors that are more commonly diagnosed are adenoid cystic carcinomas and mucoepidermoid carcinomas. Because of their diversity and overlapping features, these tumors require complex methods of evaluation. Diagnostic procedures include imaging techniques combined with clinical examination, fine needle aspiration and histopathological investigation of the excised specimens. This narrative review describes the advances in the diagnosis methods of these unusual tumors-from histomorphology to artificial intelligence algorithms.

Genetic Rearrangements in Different Salivary Gland Tumors: A Systematic Review

Salivary gland tumors (SGT) encompass a wide range of neoplasms, each with its own unique histological type and clinical presentation. This review hones in on prevalent subtypes of SGTs, including adenoid cystic carcinoma (ACC), salivary duct carcinoma (SDC), and polymorphous adenocarcinoma (PAC). The articles, identified through specific keywords, were meticulously screened in databases like PubMed, Scopus, Google Scholar, and Web of Science from 2018 to 2023. Eight articles delved into genetic modifications among the selected SGT types. A fusion protein known as MYB-NF1B is typically associated with ACC, promoting cell proliferation while inhibiting apoptosis. The presence of MYB modifications in ACCs is a beacon of hope, as it is linked to a more favorable prognosis. In contrast, SDCs often exhibit HER2 expression. The invasive nature of SGTs contributes to their resistance to treatment. In the case of PAC, the role of PRKD1 is particularly noteworthy. PRKD1, integrated with other genes from the PRKD1/2/3 cluster, helps to differentiate PAC from other diseases. Furthermore, the genetic profiles of KTN1-PRKD1) and PPP2R2A:PRKD1 are distinct. The significant genetic variability among SGTs necessitates meticulous examination. This field is in a constant state of evolution, with new discoveries reshaping our understanding. Genetics is a key player in deciphering SGTs and tailoring treatments. This complex neoplasm demands ongoing research to uncover all genetic influences, thereby enhancing diagnostic methodologies, therapeutic strategies, and patient outcomes.

Salivary gland-type cancers: cross-organ demographics of a rare cancer

BACKGROUND

Salivary gland-type cancers (SGTCs) are histologically heterogeneous and can affect organs other than the salivary glands. Some tumors outside the salivary glands are diagnosed on their unique histological characteristics. Comprehensive cross-organ studies on SGTCs are limited.

METHODS

We retrospectively analyzed the data of patients with salivary duct carcinoma (SDC), adenoid cystic carcinoma (AdCC), mucoepidermoid carcinoma (MEC), epithelial-myoepithelial carcinoma (EMC), acinic cell carcinoma (AcCC), and polymorphous adenocarcinoma (PAC) who visited our institution between 2009 and 2019. The primary tumor sites were classified into four categories; major salivary glands, head/neck (H/N) excluding (exc) major salivary glands (MSG) regions, broncho-pulmonary regions, and "others". H/N exc MSG was further divided into three subcategories, nasal/paranasal sinus, oral and pharynx/larynx.

RESULTS

We identified 173 patients with SGTCs, with SDC, AdCC, MEC, EMC, AcCC, and PAC accounting for 20%, 42%, 27%, 3%, 8%, and 1% of the cases, respectively. The most frequent primary site was the major salivary glands (64%), followed by H/N exc MSG regions (27%), broncho-pulmonary regions, and "others", thus non-salivary gland origins accounted for 9% of all cases. Patients with SDC, MEC, AcCC, or SGTC of the major salivary glands and broncho-pulmonary regions were more frequently treated by surgery. The overall survival time of the patients with MEC was significantly better than that of patients with SDC or EMC.

CONCLUSIONS

This cross-organ study highlights the clinical significance of SGTCs, underscoring the need for developing novel therapies for this rare disease entity.