Molecular Pathology of Salivary Gland Neoplasms: Diagnostic, Prognostic, and Predictive Perspective

A rare case of hyalinizing clear cell carcinoma of the tongue root: A case report and literature review

The present study describes a rare case of hyalinizing clear cell carcinoma (HCCC) of the tongue root and provides an analysis and review of the relevant literature to improve the understanding of its diagnosis and treatment. Clinical imaging and pathological data from a patient with primary HCCC of the tongue root were summarized, and previously published studies were reviewed through a literature search. The common symptoms, treatment strategies and prognoses reported in the literature were compared. A total of 16 cases of primary HCCC of the tongue were retrieved. Histologically, these cases had tumors characterized by clear cells arranged in sheets, nests and cords within the fibrous interstitium surrounding tumor cells, with round to oval cell nuclei occasionally containing small or inconspicuous nucleoli. Immunohistochemistry showed positive tumor cell staining for cytokeratin (CK)5/6, CK7 and p63, and negative for S-100, smooth muscle actin and calponin. Clinical symptoms included dysphagia, a painless mass, tongue root ulceration and a foreign body sensation in the throat. Treatment strategies included surgery, radiation therapy, repair and reconstruction, with no local recurrence or metastasis at any follow-up point. The present findings indicated that HCCC of the salivary glands is an inert malignant tumor, and a good prognosis can be achieved with both surgical resection and radiation therapy.

Intraductal papilloma of minor salivary gland: a case report and literature review

Intraductal papilloma is a rare benign neoplasm arising from the secretory ducts of the salivary glands. A 79-year-old man with an intraductal papilloma located in the minor salivary gland of sublingual mucosa was reported. The lesion, characterized by extensive internal papillomatous hyperplasia, was confirmed through histopathology and immunohistochemistry. We conducted a literature review to clarify intraductal papilloma and differences between inverted ductal papilloma, highlighting the significance of CK7 and MUC-1 immunohistochemical staining in diagnosing intraductal papilloma.

A Recognition System for Diagnosing Salivary Gland Neoplasms Based on Vision Transformer

Salivary gland neoplasms (SGNs) represent a group of human neoplasms characterized by a remarkable cytomorphologic diversity, which frequently poses diagnostic challenges. Accurate histologic categorization of salivary gland tumors is crucial to make precise diagnoses and guide decisions regarding patient management. Within the scope of this study, a computer-aided diagnosis model using Vision Transformer (ViT), a cutting-edge deep learning model in computer vision, was developed to accurately classify the most prevalent subtypes of SGNs. These subtypes include pleomorphic adenoma, myoepithelioma, Warthin tumor, basal cell adenoma, oncocytic adenoma, cystadenoma, mucoepidermoid carcinoma, and salivary adenoid cystic carcinoma. The data set comprised 3046 whole slide images of histologically confirmed salivary gland tumors, encompassing nine distinct tissue categories. SGN-ViT exhibited impressive performance in classifying the eight salivary gland tumors, achieving an accuracy of 0.9966, an area under the receiver operating characteristic curve value of 0.9899, precision of 0.9848, recall of 0.9848, and an F1 score of 0.9848. Diagnostic performance of SGN-ViT surpassed that of benchmark models. In a subset of 100 whole slide images, SGN-ViT demonstrated comparable diagnostic performance to that of the chief pathologist while significantly reducing the diagnosis time. These observations indicate that SGN-ViT holds the potential to serve as a valuable computer-aided diagnostic tool for salivary gland tumors, enhancing the diagnostic accuracy of junior pathologists.

EWSR1::CREM rearranged intra-abdominal malignant epithelioid neoplasm: two new cases of an emerging entity with clinicopathological characteristics and histological pitfalls

The EWSR1::CREM rearranged intra-abdominal malignant epithelioid neoplasm is an emerging tumor, with only a few publications describing it to date. Here, we report two new cases of this highly aggressive tumor, primarily involving the peritoneal surface. The tumors presented as a widespread diffuse peritoneal lesion associated with a 4-cm pelvic mass in a 28-year-old woman (Case 1) and as a 10-cm intra-abdominal mass infiltrating the stomach with multiple hepatic metastases in a 53-year-old woman (Case 2). The tumors shared predominant epithelioid morphology with minimal nuclear polymorphism. One of them additionally harbored spindle and rhabdoid cell populations. Both tumors displayed immunoreactivity for pan-cytokeratins, EMA, and CD99, and variable positivity for MUC4, progesterone and estrogen receptors, pan-NTRK, and synaptophysin. This misleading histology and immunophenotype give rise to a wide spectrum of differential diagnoses and highlight the crucial role of RNA sequencing in diagnostic accuracy and thus in appropriate therapeutic approaches.

Primary cell culture and characterization of a pleomorphic adenoma. A case report

Objective

This case report aimed to characterize primary pleomorphic adenoma cells obtained from a parotid gland tumor through tissue biopsy, primary cell culture, and immunohistochemical analysis.

Methods

A tissue biopsy sample from a 58-year-old patient with pleomorphic adenoma underwent histopathological examination and primary cell culture. The primary cells were characterized through immunohistochemical staining using antibodies against S-100, SMA, Vimentin, and cytokeratin AE1/AE3. Additionally, paraffin-embedded tissue sections were stained using cytokeratin AE1/AE3, Vimentin, Calponin, SMA, S100, and p63.

Results

Primary cell culture revealed weak S-100 staining and positive SMA in myoepithelial cells, while Vimentin and AE1/AE3 were negative in all the cell population. In the paraffin-embedded tissue, cytokeratin exhibited strong cytoplasmic and membranous positivity in luminal cells. Vimentin showed cytoplasmic staining in myoepithelial cells. S-100 displayed weak nuclear and strong cytoplasmic immunoreactivity in myoepithelial cells. SMA presented weak membranous positivity in a few myoepithelial cells, and finally, p63 showed nuclear staining in abluminal cells. Calponin showed negative staining in neoplastic cells and stroma.

Conclusion

The results showed that primary component of pleomorphic adenoma comprises myoepithelial cells. The identification of cell cultured in vitro is pivotal in comprehending the cellular components of these neoplasms. This comprehensive characterization of primary pleomorphic adenoma cells provides insights into their morphology, immunophenotype, and histological features.

Reappraisal of Oncocytic Adenocarcinoma: Unveiling Its Connection to Oncocytic Variants of Salivary Duct Carcinoma and Mucoepidermoid Carcinoma Through ImmunoHisto-Molecular Perspectives

Oncocytic adenocarcinoma (OC) of the salivary glands is a rare and controversial entity. It was recently reclassified as "salivary carcinoma NOS and emerging entities" in the 2022 WHO classification of head and neck tumors. The lack of specific molecular alterations and its potential affiliation with other salivary gland carcinomas, such as the oncocytic mucoepidermoid carcinomas (OMEC) or the oncocytic subtype of salivary duct carcinomas (OSDC) justified this reclassification. It is becoming essential to clarify the complex spectrum of potential diagnoses surrounding oncocytic tumors. The objective of this study was to explore the histologic features, as well as the immunohistochemical and molecular profiles, of cases previously diagnosed as OC or OMEC of the salivary glands. This study involved 28 cases of carcinomas with a predominantly oncocytic component. The sex distribution was equal. The median age was 59 years (range 10 to 89). Most of these cases originated from the parotid gland (25/28). The mean tumor size was 2.4 cm (range 0.5 to 6.5). Primary immuno-morphological and mutation/gene fusion profiles reclassified mainly (64.3%, 18/28). Most of them were reclassified in descending order as OSDC (8/18), OMEC (5/18), and OC (2/18). But 3 cases remained unclassified (3/18). The transcriptomic analysis found a proximity of their transcriptomic profile with the OMEC group and a distance from the OSDCs. These findings imply that OC is not distinct but represents oncocytic variants of other salivary carcinomas. It underscores the importance of thorough morphologic, immunohistochemical, and molecular examinations to accurately diagnose carcinomas with predominant oncocytic components in the salivary glands.

The Immunoexpression and Prognostic Significance of Stem Cell Markers in Malignant Salivary Gland Tumors: A Systematic Review and Meta-Analysis

Background/Objectives: Salivary gland carcinomas encompass a broad group of malignant lesions characterized by varied prognoses. Stem cells have been associated with the potential for self-renewal and differentiation to various subpopulations, resulting in histopathological variability and diverse biological behavior, features that characterize salivary gland carcinomas. This study aims to provide a thorough systematic review of immunohistochemical studies regarding the expression and prognostic significance of stem cell markers between different malignant salivary gland tumors (MSGTs). Methods: The English literature was searched via the databases MEDLINE/PubMed, EMBASE via OVID, Web of Science, Scopus, and CINHAL via EBSCO. The Joanna Briggs Institute Critical Appraisal Tool was used for risk of bias (RoB) assessment. Meta-analysis was conducted for markers evaluated in the same pair of diseases in at least two studies. Results: Fifty-four studies reported the expression of stem cell markers, e.g., c-KIT, CD44, CD133, CD24, ALDH1, BMI1, SOX2, OCT4, and NANOG, in various MSGTs. Low, moderate, and high RoB was observed in twenty-five, eleven, and eighteen studies, respectively. Meta-analysis revealed an outstanding discriminative ability of c-KIT for adenoid cystic carcinoma (AdCC) over polymorphous adenocarcinoma [P(LG)A] but did not confirm the prognostic significance of stem cell markers in MSGTs. Conclusions: This study indicated a possible link between stem cells and the histopathological heterogeneity and diverse biological behavior that characterize the MSGTs. c-KIT might be of diagnostic value in discriminating between AdCC and P(LG)A.

Identification and validation of cigarette smoking-related genes in predicting prostate cancer development through bioinformatic analysis and experiments

The morbidity and mortality rates of prostate cancer (PCa) are high among elderly men worldwide. Several factors, such as heredity, obesity, and environment are associated with the occurrence of PCa. Cigarette smoking, which is also an important factor in the development of PCa, can lead to genetic alterations and consequently promote PCa development. However, the smoking-induced genetic alterations in PCa are unclear. This study aimed to identify the potential smoking-related genes associated with PCa development. The smoking-related differentially expressed genes (DEGs) were identified using the Gene Expression Omnibus (GEO) which included lots of PCa datasets. DEGs were subjected to protein-protein interaction (PPI) network analysis to identify the hub genes. The pathways in which these hub genes were enriched were identified. The Cancer Genome Atlas (TCGA) dataset was used to examine the expression of smoking-related genes in PCa samples and estimate their value in predicting tumor progression and prognosis. In total, 110 smoking-related DEGs were got from GSE68135 dataset which included microarray data of PCa patients with smoking or not and 14 smoking-related key genes associated with PCa were identified from PPI network. The expression of the following seven key genes was altered in TCGA PCa patients: EWSR1, SRSF6, COL6A3, FBLN1, DCN, CYP2J2, and PLA2G2A. EWSR1, SRSF6, FBLN1, and CYP2J2 also influenced PCa progression. Additionally, EWSR1 influenced disease-free survival. In the logistic regression model, CYP2J2, which exhibited the highest risk scores, was identified as the risk gene for PCa. We also found one of the smoking-related genes: EWSR1 was truly upregulated in clinical PCa patients and influenced PCa cells invasion and proliferation. This study identified the function of smoking-related genes involved in the progression of PCa.

Insights into the molecular alterations of PLAG1 and HMGA2 associated with malignant phenotype acquisition in pleomorphic adenoma

Pleomorphic adenoma (PA) is the most common neoplasm of the salivary gland, presenting with a variety of histological features. In some cases, PA can undergo malignant transformation to carcinoma ex pleomorphic adenoma (CXPA). The transition from PA to CXPA is associated with complex molecular alterations, particularly involving the pleomorphic adenoma gene 1 (PLAG1) and high mobility group protein gene (HMGA2). This review investigates the molecular alterations of PLAG1 and HMGA2 in all domains in the malignant transformation of PA. Our analysis highlights that these markers are key alterations in the etiopathogenesis of PA and CXPA, with gene fusion and amplification being frequently reported mechanisms. Although the exact role of PLAG1 and HMGA2 in the oncogenic process remains unclear, further studies on the HMGA2 and PLAG1, are needed particularly in HMGA2-PLAG1-IGF2 which is proving to be a potential pathway for the development of clinically applicable therapies, especially for CXPA management.

Long read sequencing identifies complex structural variant landscape and recurrent TERT rearrangements in mucoepidermoid carcinoma

Mucoepidermoid Carcinoma (MEC) is a common salivary malignant neoplasm. Approximately 60 % of MECs harbor translocations between CRTC1 or CRTC3 and MAML2, which are thought to drive disease pathogenesis. However, the precise structural mechanism driving this rearrangement remains uncharacterized. Here, we performed multi-omic and long read genomic sequencing, discovering a chain of alterations that created the CRTC1::MAML2 fusion, but also an unexpected MAML2 to MYBL1 rearrangement, suggesting that MYBL1 may play a larger role in salivary gland cancers than previously recognized. Furthermore, we discovered and validated recurrent TERT rearrangements and amplifications in MEC models. 5/5 MEC cell lines and 36/39 (92 %) primary MEC tumors harbored a TERT rearrangement or copy number amplification. Custom sequencing of the TERT locus confirmed translocation breakpoints in 13/33 (39 %) MECs, while exome sequencing confirmed frequent TERT amplifications. Critically, TERT knockdown in NCI-H292, a cell line with TERT promoter rearrangement, reduced clonogenic cell survival, supporting a critical role of this gene in MEC tumorigenesis. Overall, our data suggest that complex chromothripsis rearrangement mechanisms drive the formation of structural variation in CRTC1::MAML2 fusion positive and negative tumors and reveal highly recurrent structural variation driving TERT rearrangement in MEC.

Precision medicine for patients with salivary gland neoplasms: Determining the feasibility of implementing a next-generation sequencing-based RNA assay in a hospital laboratory

Objective

Diagnosing neoplasms of the salivary gland is challenging, as morphologic features of these tumors are complex, and well-defined diagnostic categories have overlapping features. Many salivary gland neoplasms are associated with recurrent genetic alterations. The utilization of RNA-based targeted next-generation sequencing (NGS) panels for the detection of cancer-driving translocations and mutations is emerging in the clinical laboratory. Our objective was to conduct a proof-of-concept study to show that in-house molecular testing of salivary gland tumors can enhance patient care by supporting morphologic diagnoses, thereby improving therapeutic strategies such as surgical options and targeted therapies.

Material and Methods

Residual formalin-fixed paraffin-embedded salivary gland neoplasm specimens from a cohort of 17 patients were analyzed with the Archer FusionPlex Pan Solid Tumor v2 panel by NGS on an Illumina NextSeq550 platform.

Results

We identified structural gene rearrangements and single nucleotide variants in our patient samples that have both diagnostic and treatment-related significance. These alterations included PLAG1, MAML, and MYB fusions and BRAF, CTNNB1, NRAS, and PIK3CA mutations.

Conclusion

Our RNA-based NGS assay successfully detected known gene translocations and mutations associated with salivary gland neoplasms. The genetic alterations detected in these tumors demonstrated potential diagnostic, prognostic, and therapeutic value. We suggest that incorporating in-house ancillary molecular testing could greatly enhance the accuracy of salivary gland fine needle aspiration cytology and small biopsies, thereby better guiding surgical decisions and the use of targeted therapies.

NanoString nCounter-Based Assay for Detection of Fusion-Associated Salivary Gland Tumors

PURPOSE

Salivary gland tumors include numerous subtypes that vary from benign to highly aggressive, with many showing overlapping histopathological features that can make diagnosis challenging. Most subtypes express driver fusion genes that are tumor specific, and detection of such fusions is useful for differentiating amongst specific diagnoses, determining appropriate tumor grading, and guiding effective treatment. Currently, fusions can be detected by FISH, RT-PCR or through next-generation sequencing approaches, all of which are highly effective methodologies but can be costly or time consuming.

METHODS

We developed a rapid NanoString nCounter platform-based assay to detect salivary gland tumor fusions using a combination of fusion junction-specific probes and an approach through differential exon expression analysis. The assay includes 68 junction-specific probes and analysis of exon expression across 9 fusion-associated genes in a single multiplex assay.

RESULTS

Out of 55 retrospective and 171 prospective cases assayed, we accurately detected the majority of cases of pleomorphic adenoma, adenoid cystic carcinoma, cribriform adenocarcinoma, clear cell carcinoma, secretory carcinoma and NUT-rearranged carcinoma, including cases of these tumor types arising in non-salivary gland sites, with the major drawback being an inability to detect MAML2-containing mucoepidermoid samples. With mucoepidermoid carcinoma excluded, the assay shows an overall sensitivity of 96.1% and specificity of 100%.

CONCLUSION

We show that the majority of salivary gland tumor fusions can be effectively detected with a single rapid NanoString based assay, which can serve as a useful adjunctive tool for routine diagnostic head and neck pathology. The assay is low cost with a rapid turnaround time (30 h total assay time per sample batch, with minimal technician input required) compared to alternate detection methods.

Rare Head and Neck Cancers and Pathological Diagnosis Challenges: A Comprehensive Literature Review

Head and neck cancers (HNCs) arise from anatomically adjacent sites and subsites, with varying etiological factors, diagnostic strategies, prognoses, and treatment approaches. While conventional squamous cell carcinoma (SCC) is the most common histology in the head and neck district, HNCs encompass a variety of rare histopathological entities, categorized into epithelial tumors such as salivary gland cancers, sinonasal tumors, neuroendocrine tumors, malignant odontogenic tumors, and SCC variants versus non-epithelial tumors including soft tissue sarcomas, mucosal melanomas, and hematological malignancies. Rare HNCs (R-HNCs) represent a diagnostic and clinical challenge, requiring histopathological expertise, the availability of peculiar molecular analysis, and the personalization of local and systemic treatments, all guided by a multidisciplinary tumor board. Here, we provide a comprehensive literature review on R-HNCs, emphasizing key histopathological and molecular characteristics that are crucial for guiding treatment decisions. An insight about the latest developments in systemic treatments is also reported.

Clinical Behavior and Molecular Insights of Secretory Carcinoma of Salivary Glands, a Single Center Experience

OBJECTIVE

the study aimed to characterize the novel entity referred to as secretory carcinoma of the salivary glands.

METHODS

we comprehensively evaluated 150 patients afflicted by malignant salivary gland tumors who had been under treatment at the University of Verona. Inclusion criteria primarily focused on the availability of paraffin block materials and adequate follow-up data. Subsequently, we conducted a comprehensive Fluorescent In Situ Hybridization (FISH) analysis, utilizing probes targeting NTRK-3, MALM-2, EWRS-1, HER-2, MDM-2, and NTRK1-2.

RESULTS

out of the initial cohort, 37 patients met the eligibility criteria for our study. We identified NTRK3 gene rearrangements in four patients (11%), two of whom had mucoepidermoid carcinoma, and the remaining two had acinic cell carcinoma. Notably, none of these patients had initially received a secretory carcinoma diagnosis. The primary treatment approach for all patients entailed surgical parotid gland resection. The overall survival (OS) for patients with NTRK3 rearrangements amounted to 78 months, with a corresponding progression-free survival (PFS) of 73 months.

CONCLUSION

in summary, our case series suggests that secretory carcinomas exhibit a favorable clinical course and underscores the pivotal importance of distinguishing secretory carcinomas from other histological subtypes.

Microsecretory adenocarcinoma of the hard palate: a case report and literature review

Microsecretory adenocarcinoma (MSA) is a new type of salivary gland neoplasm identified in the 2022 World Health Organization Classification of Head and Neck Tumour (Skalova et al., Head Neck Pathol 16:40-53, 2022) and is characterized by a unique set of histomorphologic and immunohistochemical features and a recurrent MEF2C::SS18 fusion. MSA was initially misdiagnosed as another salivary gland tumour due to its similar morphology; until recently, only fewer than 50 cases were reported. We present a case of MSA of the hard palate with diverse architectural growth patterns, bland cytological features, abundant basophilic intraluminal secretions and fibromyxoid stroma. The tumour cells were positive for the SOX10, S100, and p63 protein and negative for the p40 protein according to immunohistochemistry. SS18 gene rearrangement was demonstrated via break-apart fluorescence in situ hybridization. We also provided a comprehensive literature review and integrated the clinicopathological features, immunophenotype, and molecular alterations of the disease. A comprehensive understanding of MSA enables us to accurately distinguish and categorize MSA from other salivary gland tumours with analogous morphologies.

Utility of fine-needle aspiration biopsy (FNAB) in parotid pleomorphic adenoma diagnosis and management

PURPOSE

Pleomorphic adenoma (PA), the most common benign tumour of the parotid gland, requires accurate preoperative diagnosis owing to its capacity for malignant transformation. The aim of this study was to evaluate our experience with ultrasound-guided fine-needle aspiration biopsy (FNAB) in the diagnostic algorithm for patients with PA and to assess clinical outcomes for those with different surgical approaches.

MATERIAL AND METHODS

We carried out a retrospective analysis of patients treated for parotid gland mass between 2010 and 2016. These had had preoperative FNAB and had undergone subsequent surgery.

RESULTS

165 patients had FNAB with the result of PA and the definitive histology confirmed PA in 159 cases (96.4%). On the other hand, in 179 patients, the definitive histology showed PA and the preoperative FNAB result corresponded in 159 cases (88.9%). The measured sensitivity, specificity and accuracy of ultrasound-guided FNAB in the diagnosis of PA were, respectively, 88.83%, 96.23% and 92.31%. Most of the patients underwent superficial or partial superficial parotidectomy, followed by extracapsular dissection which was associated with statistically lower risk of facial nerve injury (P=0.04).

CONCLUSION

Ultrasound-guided FNAB is simple, accurate and valuable in the diagnosis of PA and provides results that can lead to the choice of less invasive operative treatment.

Uncovering the WWTR1::NCOA2 Gene fusion in low-grade myoepithelial-rich neoplasm with HMGA2 expression: A case report

We describe a case of a pleomorphic adenoma (PA) arising from the para-tracheal accessory salivary gland in a 44-year-old male harboring a novel WWTR1::NCOA2 gene fusion. To our knowledge, this novel gene fusion has not been described previously in salivary gland tumors. The patient presented with hoarseness of voice. The radiological exam revealed a mass in the upper third of the trachea involving the larynx. Histologically, the tumor consisted of bland-looking monocellular eosinophilic epithelial cells arranged in cords and sheets separated by thin fibrous stroma, focally forming a pseudo-tubular pattern. In immunohistochemistry, the tumor cells demonstrated positivity for CK7, PS100, SOX10, and HMGA2; and negativity for CK5/6, p40 p63, and PLAG1. In addition, the clustering analysis clearly demonstrates a clustering of tumors within the PA group. In addition to reporting this novel fusion in the PA spectrum, we discuss the relevant differential diagnoses and briefly review of NCOA2 and WWTR1 gene functions in normal and neoplastic contexts.

Molecular Aspects of Mucoepidermoid Carcinoma and Adenoid Cystic Carcinoma of the Salivary Gland

BACKGROUND

Salivary gland tumors (SGTs) are rare and highly heterogeneous lesions, making diagnosis a challenging activity. In addition, the small number of studies and samples evaluated difficults the determination of prognosis and diagnosis. Despite the solid advances achieved by research, there is still an intense need to investigate biomarkers for diagnosis, prognosis and that explain the evolution and progression of SGTs.

METHODS

We performed a comprehensive literature review of the molecular alterations focusing on the most frequent malignant SGTs: mucoepidermoid carcinoma and adenoid cystic carcinoma.

RESULTS

Due to the importance of biomarkers in the tumorigenenic process, this review aimed to address the mechanisms involved and to describe molecular and biomarker pathways to better understand some aspects of the pathophysiology of salivary gland tumorigenesis.

CONCLUSIONS

Molecular analysis is essential not only to improve the diagnosis and prognosis of the tumors but also to identify novel driver pathways in the precision medicine scenario.

Oncocytic Lesions of Salivary Glands: Morphological, Immunohistochemical, and Molecular Findings

The fifth edition of the World Health Organization (WHO) classification introduces new diagnostic methods based on genetic alterations, providing insight into the molecular basis of lesions. As a result, the classification system has evolved, new entities have been introduced, and existing entities have been reclassified. Oncocytic lesions of salivary glands are a group of neoplastic conditions characterized by the presence of oncocytic cells. These lesions present a diagnostic challenge due to their overlapping histological features. Therefore, a comprehensive evaluation, including morphological, immunohistochemical, and molecular analysis, is crucial for accurate diagnosis and appropriate management. Accurate classification of salivary gland pathologies is essential for selecting the appropriate treatment methods and predicting outcomes. The introduction of new therapeutic approaches, such as targeted therapies for malignant salivary gland tumors, has improved patient outcomes. However, to effectively implement these therapies in clinical practice, a clear classification of lesions is necessary.

Molecular Factors in Carcinoma Ex Pleomorphic Adenoma: Systematic Review and Meta-Analysis

OBJECTIVE

Carcinoma ex pleomorphic adenoma (CXPA) is a rare malignant salivary gland tumor. Although multiple reviews have been published on salivary gland malignancies, it has been a decade since the last dedicated systematic review pertaining to CXPA alone was published. This study examines molecular factors in CXPA diagnosis.

DATA SOURCES

MEDLINE, CINAHL, Embase, Scopus, Web of Science (BIOSIS), Cochrane CENTRAL, Health Collection (Informit), OpenDOAR, and GreyNet International.

REVIEW METHODS

Systematic review and meta-analysis from inception to October 31, 2022 for all English language studies pertaining to "carcinoma ex pleomorphic adenoma." Predicted incidence of each biomarker was calculated with meta-analysis. Comparison against pleomorphic adenoma (PA) and salivary duct carcinoma (SDC) when reported within the same study are performed. Risk of bias performed with JBI tool for prevalence studies.

RESULTS

Of 19151 unique studies undergoing abstract screening, 55 studies (n = 1322 patients) underwent data analysis. Biomarkers with >3 studies were p53, HER2, AR, EGFR, PLAG1, ERBB, ER, PR, HMGA2, p16, p63, a-SMA, RAS, PTEN, PDL1, BRAF, PIK3CA, and c-kit. Highest incidence was seen in AR, EGFR, p16, and p53. Significant differences were demonstrated compared with PA and SDC. There was high heterogeneity and overall high risk of bias within studies.

CONCLUSION

Molecular factors are an area of interest in the diagnosis of CXPA. Our study results support examining CXPA as a discrete cohort in future targeted therapy trials. Laryngoscope, 134:1042-1053, 2024.

Primary and Recurrent Intraosseous Adenoid Cystic Carcinoma-Analysis of Two Cases and Literature Review

Adenoid cystic carcinoma (ACC) is a rare malignant tumor that mostly occurs in minor glands, especially in the palate. Intraosseous adenoid cystic carcinoma (IACC) is rarer. There is no clear conclusion on the clinical, radiologic and pathological characteristics of IACC because of few reported IACC cases, leading to insufficient understanding of IACC. We reviewed 52 previous reports of primary IACC (PIACC) and analyzed the clinical features of those patients involved, attempting to provide a better understanding of PIACC. Moreover, we present a case of primary PIACC and a case of recurrent IACC (RIACC). The two patients showed similarities in clinical and pathological results, along with slight differences in radiological and immunohistochemical results. The patient of case 1 seemed to display a worse prognosis, which can only be proved after long term follow-up.

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

PURPOSE

The correct classification of salivary gland pathologies is crucial for choosing a treatment method and determining the prognosis. Better outcomes are now achievable thanks to the introduction of new therapy approaches, such as targeted therapies for malignant salivary gland tumors. To apply these in clinical routine, a clear classification of the lesions is required.

METHODS

The following review examines all changes from the first World Health Organization (WHO) Classification of salivary gland pathologies from 1972 to fifth edition from 2022. Possible developments in the diagnosis and classification of salivary gland pathology are also presented.

RESULTS

The current WHO classification is the fifth edition. With the development of new diagnostic methods, based on genetic alterations, it provides insight into the molecular basis of lesions. This has resulted in the evolution of classification, introduction of new entities and reclassification of existing ones.

CONCLUSIONS

Genetic alterations will become increasingly more significant in the identification of salivary gland pathologies in the future. These alterations will be helpful as prognostic and predictive biomarkers, and may also serve as targets for anti-cancer therapies.

Basal cell adenoma of parotid gland: two case reports and literature review

Most of salivary tumors are benign in nature and are typically diagnosed and classified based on their histopathological presentation. Basal cell adenoma of the salivary glands is a rare, benign disease accounting for 1% to 3% of salivary gland tumors. Despite its low incidence, basal cell adenoma is the third most common benign tumor of the salivary gland after pleomorphic adenoma and Warthin's tumor. It usually appears as a firm and slow-growing mass. Due to the prognosis, differential diagnosis with basal cell adenocarcinoma, adenoid cystic carcinoma and basaloid squamous cell carcinoma is required. In this report, we present two cases; a 62-year-old woman who presented with an asymptomatic, and slow-growing mass and a 64-year-old woman with a static-sized mass in the parotid gland. In both cases, the mass was completely excised, postoperative pathology reports confirmed the diagnosis of basal cell adenoma. We also review the literature and discuss this rare entity.

The Epigenesis of Salivary Glands Carcinoma: From Field Cancerization to Carcinogenesis

Salivary gland carcinomas (SGCs) are a diverse collection of malignant tumors with marked differences in biological activity, clinical presentation and microscopic appearance. Although the etiology is varied, secondary radiation, oncogenic viruses as well as chromosomal rearrangements have all been linked to the formation of SGCs. Epigenetic modifications may also contribute to the genesis and progression of SGCs. Epigenetic modifications are any heritable changes in gene expression that are not caused by changes in DNA sequence. It is now widely accepted that epigenetics plays an important role in SGCs development. A basic epigenetic process that has been linked to a variety of pathological as well as physiological conditions including cancer formation, is DNA methylation. Transcriptional repression is caused by CpG islands hypermethylation at gene promoters, whereas hypomethylation causes overexpression of a gene. Epigenetic changes in SGCs have been identified, and they have been linked to the genesis, progression as well as prognosis of these neoplasms. Thus, we conduct a thorough evaluation of the currently known evidence on the involvement of epigenetic processes in SGCs.

Limited parotid surgery as sole form of treatment for carefully selected malignant tumours of the parotid gland: Still sufficient on the long-term?

BACKGROUND

The aim of the study was to investigate the oncological and functional outcome following extracapsular dissection as the sole form of treatment in locally limited low-grade malignant parotid tumours in the long term.

METHODS

The records of all patients treated for T1-T2 low-grade malignant tumours of the parotid gland solely by means of extracapsular dissection between 2005 and 2017 were studied retrospectively.

RESULTS

A total of 16 cases formed our study sample (7 men, 9 women). Their mean age was 50.2 years (21-84 years). Mean follow-up was 107 months (60-201 months). In 6 cases the tumour was an acinic cell carcinoma, in 9 cases a mucoepidermoid carcinoma and in one case a basal cell adenocarcinoma. Regarding the T category, the tumour was Tis in one case, T1 in 12 cases and T2 in three cases. The five-year disease-specific survival rate was 100 %, as was local disease control. Facial nerve function was House-Brackmann grade I without exception.

CONCLUSIONS

Our study showed very encouraging long-term results following primary extracapsular dissection as the sole surgical therapy for carefully selected low-stage, low-grade, inferiorly located lesions in patients with high compliance.

LAY SUMMARY

The "one-size-fits-all" strategy of complete parotidectomy with neck dissection might be tantamount to overtreatment by less aggressive cases of parotid cancer. Extracapsular dissection seems to be oncologically sufficient for carefully selected T1-T2 low-grade cases in the long-term in patients with ensured follow-up.

Molecular Targets in Salivary Gland Cancers: A Comprehensive Genomic Analysis of 118 Mucoepidermoid Carcinoma Tumors

INTRODUCTION

Salivary gland carcinomas (SGC) are histologically diverse cancers and next-generation sequencing (NGS) to identify key molecular targets is an important aspect in the management of advanced cases.

METHODS

DNA was extracted from paraffin embedded tissues of advanced SGC and comprehensive genomic profiling (CGP) was carried out to evaluate for base substitutions, short insertions, deletions, copy number changes, gene fusions and rearrangements. Tumor mutation burden (TMB) was calculated on approximately 1.25 Mb. Some 324 genes in the FoundationOne CDX panel were analyzed.

RESULTS

Mucoepidermoid carcinoma (MECa) mutations were assessed. CDKN2A and CDKN2B GA were common in mucoepidermoid carcinoma (MECa) (52.5 and 30.5%). PIK3CA was also common in MECa (16.9%). ERBB2 amplification/short variants (amp/SV) were found in MECa (5.9/0%). HRAS GA was common in MECa (14.4%) as well. Other targets, including BAP1, PTEN, and KRAS, were noted but had a low incidence. In terms of immunotherapy (IO)-predictive markers, TMB > 10 was more common in MECa (16.9%). PDL1 high was also seen in MECa (4.20%).

CONCLUSION

SGC are rare tumors with no FDA-approved treatment options. This large dataset reveals many opportunities for IO and targeted therapy contributing to the continuously increased precision in the selection of treatment for these patients.

Transcriptomic insights into adenoid cystic carcinoma via RNA sequencing

Background: The aim of this study was to investigate the underlying mechanisms of adenoid cystic carcinoma (ACC) at the transcriptome level. Materials and methods: We obtained paired tumor and normal salivary gland tissues from 15 ACC patients, which were prepared for RNA sequencing. Results: Gene enrichment analysis revealed that the upregulated pathways were mainly involved in axonogenesis, and the downregulated pathways were mainly related to leukocyte migration, the adaptive immune response, lymphocyte-mediated immunity, and the humoral immune response. T-cells, B-cells and NK cells showed low infiltration in ACC tissues. In addition to the gene fusions MYB-NFIB and MYBL1-NFIB, a new gene fusion, TVP23C-CDRT4, was also detected in 3 ACC tissues. PRAME was significantly upregulated in ACC tissues, while antigen-presenting human leukocyte antigen (HLA) genes were downregulated. Conclusion: We found a new gene fusion, TVP23C-CDRT4, that was highly expressed in ACC. PRAME may be an attractive target for ACC immunotherapy.

INFLUENCE OF THE PATIENT'S SEX AND AGE, VOLUMES OF THE SALIVARY GLAND AND PLEOMORPHIC ADENOMA ON THE TUMOR HISTOLOGICAL VARIANTS

OBJECTIVE

Aim: The purpose of the study was to identify the influence of the patient's sex and age, the volumes of the salivary gland and pleomorphic adenoma on the histological variants of the tumor.

PATIENTS AND METHODS

Materials and Methods: The study included 21 women and 9 men with pleomorphic adenomas of the salivary gland. In 15 cases, a mesenchymal variant of pleomorphic adenoma was identified, in 5 cases - an epithelial variant, in 10 cases - a mixed variant. The average age of the patients was 39.7±2.9 years. Patients with pleomorphic adenomas underwent magnetic resonance imaging using a Siemens MAGNETOM Aera 1.5T device (Germany), during which three projections of the tumor and salivary gland were measured (antero-posterior, lateral, vertical) with subsequent calculation of their volumes, and then the ratios of these volumes. Classification trees were used to determine whether patients belonged to one of three variants of pleomorphic adenoma. The CART (Classification And Regression Tree) algorithm was used as a branching option. Stopping branching was carried out using the FACT (Fact-style direct stopping) method until each terminal (final) node of the tree does not contain incorrectly classified observations or when their number becomes less than a given proportion of the total group size (less than 5%). Determination of the structure and relationships between the tumor variants and such indicators as gender, age and radiological indicators (volume of the tumor, volume of the salivary gland, ratio of tumor volume to salivary gland volume) was carried out using correspondence analysis.

RESULTS

Results: Epithelial variant of pleomorphic adenoma is more typical for women, and the mixed and mesenchymal variant is more common for patients of both sexes. The epithelial variant can develop in patients of any age, while the mixed variant occurs mainly in patients older than 41 years, and the mesenchymal variant - mainly in patients younger than 41 years. The ratio of the volume of the tumor to the volume of the salivary gland will be predominantly >0.17 in the epithelial variant of pleomorphic adenoma, predominantly ≤0.17 in the mesenchymal variant, and can take any value in the mixed variant.

CONCLUSION

Conclusions: The authors conducted a study in order to identify the influence of sex, age of the patient, and the ratio of the volume of pleomorphic adenoma to the volume of the salivary gland on the histological variant of the tumor. The revealed data will be useful in the treatment and diagnostic process in patients with pleomorphic adenoma of the salivary gland.

Analysis of Cytological Misdiagnosis and Oversight of Adenoid Cystic Carcinoma of Salivary Gland

OBJECTIVE

In this article on adenoid cystic carcinoma (ACC) of salivary gland, we intend to summarize the causes of misdiagnosis and oversight of ACC hoping to improve cytological diagnostic accuracy, clinical management and patient treatment.

METHODS

The study retrospectively reviewed 32 patients with ACC of salivary gland, registered at the Affiliated Hospital of Southwest Medical University from July 2014 to June 2021. These cases were diagnosed by FNA and surgical excision biopsy. All cytopathological results were retrospectively categorized according to Milan system for reporting salivary gland cytopathology (MSRSGC). The accuracy of FNA was verified by surgical excision biopsy.

RESULTS

Of these 32 patients, 16 (50.0%) cases were male, and 16 (50.0%) were female. Their age ranged from 21 to 79 years, with an average age of 50.32 years. The highest incidence (15/32, 46.9%) of ACC was observed in patients between 41 and 50 years of age. 10 cases (31.3%) occurred in the parotid gland, 9 cases (28.1%) in the submandibular gland, 9 cases (28.1%) in the sublingual gland, 3 cases (9.4%) in the palate, and 1 case (3.1%) in the lip. Among the 32 cases of ACC, 23 cases (71.9%) were classified to VI, 4 cases (12.5%) to IVa, and 5 cases (15.6%) to II by MSRSGC. A comparison of the FNA results with biopsy showed that the accuracy of FNA in ACC of salivary gland is 71.9%. Being able to identify the cytomorphological features is the key factor for accurate diagnosis of ACC of the salivary gland.

CONCLUSION

Our results confirm that FNA is an important initial screening in the diagnosis of ACC of salivary gland. Increased study of the cytomorphology of ACC is beneficial for more accurate diagnosis of ACC, to reduce misdiagnosis and oversight.

A Pediatric Case of High-Grade Secretory Carcinoma of the Maxillary Sinus With ETV6::NTRK3 Gene Fusion, Therapeutic Implications, and Review of the Literature

Secretory carcinoma (SC) is a salivary gland tumor with a generally low grade microscopic appearance, a characteristic immunophenotype, and a recurrent translocation leading to ETV6::NTRK3 fusion gene. Rare cases are reported in children. The maxillary sinus is an unusual localization. SC have an overall favorable prognosis, but cases with high grade morphology have been described in adult population and are related to a more aggressive clinical course. We present a pediatric case of secretory carcinoma involving the maxillary sinus with high grade morphology, with a review of the literature of secretory carcinomas with high grade component.

Cystic Salivary Gland Neoplasms: Diagnostic Approach With a Focus on Ancillary Studies

Cystic salivary gland cytology can be challenging due to the fact that a cystic mass can be the clinical presentation of both non-neoplastic and neoplastic conditions. Neoplastic lesions consist of both benign and malignant neoplasms. The cytomorphologic features of these entities can overlap and the cystic background may additionally contribute to the complexity of these lesions and their interpretation. Ancillary studies have been reported in several studies to be beneficial in further characterization of the cellular components and subsequent diagnosis of the cystic lesions of the salivary gland. Fluorescence in situ hybridization, real-time polymerase chain reaction, and next-generation sequencing are now being utilized to detect molecular alterations in salivary gland neoplasms. MALM2 rearrangement is the most common gene fusion in mucoepidermoid carcinoma. PLAG1 rearrangement is present in more than half of pleomorphic adenomas. AKT1:E17K mutation is the key diagnostic feature of the mucinous adenocarcinoma. NR4A3 overexpression is highly sensitive and specific for the diagnosis of acinic cell carcinoma. MYB fusion is noted in adenoid cystic carcinoma. ETV6:NTRK3 fusion is helpful in diagnosis of secretory carcinoma. p16 and human papillomavirus (HPV) studies differentiate HPV-related squamous cell carcinoma from non-HPV-related neoplasms with overlapping features. NCOA4:RET fusion protein is the main fusion in intraductal carcinoma.

Bioinformatic Analysis for Mucoepidermoid and Adenoid Cystic Carcinoma of Therapeutic Targets

Salivary gland neoplasms are a heterogeneous neoplasm group, including mucoepidermoid carcinoma (MECa), adenoid cystic carcinoma (AdCC), and many others. Objective: We aimed to identify new critical genes of MECa and AdCC using bioinformatics analysis. Methods: Gene expression profile of GSE153283 was analyzed by the GEO2R online tool to use the DAVID software for their subsequent enrichment. Protein–protein interactions (PPI) were visualized using String. Cytoscape with MCODE plugin followed by Kaplan–Meier online for overall survival analysis were performed. Results: 97 upregulated genes were identified for MECa and 86 for AdCC. PPI analysis revealed 22 genes for MECa and 63 for AdCC that were validated by Kaplan–Meier that showed FN1 and SPP1 for MECa, and EGF and ERBB2 for AdCC as more significant candidate genes for each neoplasm. Conclusion: With bioinformatics methods, we identify upregulated genes in MECa and AdCC. The resulting candidate genes as possible therapeutic targets were FN1, SPP1, EGF, and ERBB2, and all those genes had been tested as a target in other neoplasm kinds but not salivary gland neoplasm. The bioinformatic evidence is a solid strategy to select them for more extensive research with clinical impact.

Unicystic Mucoepidermoid Carcinoma: A Pitfall for Clinical and Pathologic Diagnosis

Unicystic mucoepidermoid carcinoma (UC-MEC) is a rare MEC variant, and its diagnosis is frequently problematic. This study is aimed at summarizing its clinicopathologic characteristics, treatment, and prognosis and proposing key points to avoid missed diagnosis and misdiagnosis in clinical and pathological conditions. This retrospective study included 30 UC-MEC cases, and the clinical findings were collected from the clinical medical records. Radiographic features, histologic behaviors, MAML2 rearrangement by fluorescence in situ hybridization (FISH), and follow-up data were analyzed. Moreover, glandular odontogenic cyst (GOC) and cytadenoma (CA) were used as controls. In the UC-MEC group, 19 patients were female (63%), and 11 were male (37%). The mean patient age was 39.5 (range, 7–72 years). The affected locations included the jaw (8 maxillary, 3 mandibular) and salivary glands (7 parotid, 11 palates, and 1 floor of the mouth). The chief complaint was swelling; the lesions were all cystic, among which 66.7% were well circumscribed and 33.3% poorly defined. Microscopic examination showed two UC-MEC histologic subtypes. Type A presented as a single cyst with mural thickening (8/30, 27%) lined predominantly by epidermoid cells with interspersed intermediate and mucinous cells, and type B (22/30, 73%) showed infiltrative tumor islands in the cystic wall or the surrounding tissue. FISH analysis suggested that approximately 66.7% of UC-MEC harbored a MAML2 rearrangement. During the median follow-up period of 42 months (range, 6–120 months), all type A patients and 68% of type B patients who underwent complete surgical resection lived without relapse. Seven cases with type B cancer that underwent curettage initially had local recurrence. Clinicians and pathologists hardly recognize UC-MEC owing to its cystic architecture. Specific epidermoid, mucous, and intermediate tumor cells, and MAML2 fusion testing, are essential to avoid potential diagnostic pitfalls. Prompting and completing resection surgery with negative margins would have a favorable prognosis.

Identification of differentially expressed microRNAs as potential biomarkers for carcinoma ex pleomorphic adenoma

Carcinoma ex pleomorphic adenoma (CXPA) is a rare malignancy that transforms from PA. Early detection of the carcinoma by biopsy is difficult due to similar histopathology of the malignant and benign components. To address this, we investigated and compared the characteristic miRNA expression patterns across samples of the PA, carcinomatous portions (CA) of CXPA, as well as conventional PA. We selected 13 CXPA and 16 conventional PA FFPE samples, separated the PA and CA portions of CXPA samples and conducted miRNA profiling for each group. Among 13 transcripts that were differentially expressed between PA and CA of CXPA, eight miRNAs were up-regulated and five down-regulated in CA. Bioinformatic analysis revealed that the up-regulated miRNAs were related to cancer progression and down-regulated ones to tumor suppression. Additionally, seven miRNAs were significantly up-regulated in PA of CXPA compared to conventional PA, although they are histopathologically similar. Almost all of these transcripts interacted with TP53, a well-known tumor suppressor. In conclusion, we identified differentially expressed miRNAs in PA and CA of CXPA, which were closely associated with TP53 and various cancer-related pathways. We also identified differentially expressed miRNAs in the PA of CXPA and conventional PA which may serve as potential biomarkers.

TRK Inhibition with Entrectinib in Metastatic Salivary Secretory Carcinoma (SC): A Case Report

NTRK gene fusions are rare oncogenic driver mutations that can be found in a broad range of neoplasms. In secretory carcinoma (SC), ETV6-NTRK3 gene fusion is seen in a majority of the cases and represents a druggable target for patients with advanced disease in the absence of a currently accepted standard of care. In our case, we describe a patient with recurrent, metastatic SC treated with first line entrectinib with clinically meaningful, durable ongoing response after 49 months. The patient experienced grade 1 fatigue, dysgeusia, skin sensitivity, arthralgias, an increase in serum creatinine, and weight-gain as well as grade 2 hypotension which resolved after a dose reduction. Entrectinib is a well-tolerated treatment with the potential for durable responses and TRK inhibition should be considered the standard of care in SC and other NTRK gene fusion-positive advanced neoplasms without acceptable alternative treatment options.

Mucoepidermoid carcinoma: Analysis of 76 cytologic cases and correlation with histologic grade

BACKGROUND

Mucoepidermoid carcinoma (MEC) is the most common salivary gland (SG) malignancy. In this study, the author undertook analysis of a large collection of MEC cytologic cases.

MATERIALS AND METHODS

Cytopathology files were searched for MEC cases with histopathologic confirmation. Fine-needle aspiration (FNA) smears used standard technique.

RESULTS

Seventy-six cases (63 patients [M:F = 1:1; age range, 23-87 years; mean age, 58 years]) met inclusion criteria. Aspirates were primary (54 [71%]), metastatic (18 [24%]), and locally recurrent (4 [5%]). FNA sites included parotid gland (49 [64%]), regional lymph nodes (11 [14%]), submandibular gland (5 [7%]), inner canthus of eye (2 [3%]), and lung (2 [3%]); and single specimens from palate, jaw, shoulder, paranasal sinus, floor of mouth, ear canal, and effusion. Cytologic diagnoses included MEC (30 cases [39%]), suspicious for MEC (16 [21%]), non-MEC carcinoma (9 [12%]), suspicious for malignancy (SM) (2 [3%], malignant (M) (1 [1%]), SG and/or suspicious SG neoplasm (7 [8%]), atypical (3 [5%]), nonneoplastic (5 [6%]), nondiagnostic (2 [3%]), and benign SG neoplasm (1 [1%]). A total of 26% of low-grade (LG) cases were diagnosed as malignant in contrast to 87% malignant in high-grade (HG) cases. Cytomorphology depended on tumor grade. LG MEC contained intra- and/or extra-cellular mucin and more uniform cell and/or nuclear morphology, whereas cytologic atypia, anisonucleosis, and keratotic cells were more typical of HG tumors.

CONCLUSION

A malignant (M) or suspicious for malignancy (SM) cytologic interpretation was made in 76% of mucoepidermoid carcinoma (MEC) cases. In contrast to high-grade MEC (97% identified as M/SM), only 59% of low-grade (LG) MEC cases were interpreted as such, illustrating the continued diagnostic challenge posed by LG MEC using fine-needle aspiration biopsy.

Diagnostic Value of MAML2 Rearrangements in Mucoepidermoid Carcinoma

Mucoepidermoid carcinoma (MEC) is often seen in salivary glands and can harbor MAML2 translocations (MAML2+). The translocation status has diagnostic utility as an objective confirmation of the MEC diagnosis, for example, when distinction from the more aggressive adenosquamous carcinoma (ASC) is not straightforward. To assess the diagnostic relevance of MAML2, we examined our 5-year experience in prospective testing of 8106 solid tumors using RNA-seq panel testing in combinations with a two-round Delphi-based scenario survey. The prevalence of MAML2+ across all tumors was 0.28% (n = 23/8106) and the majority of MAML2+ cases were found in head and neck tumors (78.3%), where the overall prevalence was 5.9% (n = 18/307). The sensitivity of MAML2 for MEC was 60% and most cases (80%) were submitted for diagnostic confirmation; in 24% of cases, the MAML2 results changed the working diagnosis. An independent survey of 15 experts showed relative importance indexes of 0.8 and 0.65 for "confirmatory MAML2 testing" in suspected MEC and ASC, respectively. Real-world evidence confirmed that the added value of MAML2 is a composite of an imperfect confirmation test for MEC and a highly specific exclusion tool for the diagnosis of ASC. Real-world evidence can help move a rare molecular-genetic biomarker from an emerging tool to the clinic.

The evolving role of molecular pathology in the diagnosis of salivary gland tumours with potential pitfalls

Salivary gland tumors are diagnostically challenging owing to the morphological diversity within any tumor type and overlapping histomorphology and immunohistochemistry amongst different tumours. In past two decades, rapid progress has been made in the field of understanding the pathogenesis of these tumours with the discovery of many tumour specific translocations and rearrangements. This includes CRTC1-MAML2 and CRTC-MAML2 in mucoepidermoid carcinoma, MYBNFIB and MYBL1-NFIB fusions in adenoid cystic carcinoma, PLAG1 and HMGA2 in pleomorphic adenoma, ETV6-NTRK3 in secretory carcinoma, NR4A3 rearrangements in acinic cell carcinoma, PRKD1 mutations in polymorphous adenocarcinoma and EWSR1-ATF1 in clear cell carcinoma. This review is a lens for progress made till date in the molecular pathology of salivary gland tumours with a special focus on their role as diagnostic tools and implications on clinical management of the patient as prognostic and predictive markers.

Update from the 5th Edition of the World Health Organization Classification of Head and Neck Tumors: Salivary Glands

The salivary gland section in the 5th edition of the World Health Organization Classification of Head and Neck Tumours features a description and inclusion of several new entities, including sclerosing polycystic adenoma, keratocystoma, intercalated duct adenoma, and striated duct adenoma among the benign neoplasms; and microsecretory adenocarcinoma and sclerosing microcystic adenocarcinoma as the new malignant entities. The new entry also includes mucinous adenocarcinoma subdivided into papillary, colloid, signet ring, and mixed subtypes with recurrent AKT1 E17K mutations across patterns suggesting that mucin-producing salivary adenocarcinomas represent a histologically diverse single entity that may be related to salivary intraductal papillary mucinous neoplasm (IPMN). Importantly, the number of entities in the salivary chapter has been reduced by omitting tumors or lesions if they do not occur exclusively or predominantly in salivary glands, including hemangioma, lipoma, nodular fasciitis and hematolymphoid tumors. They are now discussed in detail elsewhere in the book. Cribriform adenocarcinoma of salivary gland origin (CASG) now represents a distinctive subtype of polymorphous adenocarcinoma (PAC). PAC is defined as a clinically, histologically and molecularly heterogeneous disease group. Whether CASG is a different diagnostic category or a variant of PAC is still controversial. Poorly differentiated carcinomas and oncocytic carcinomas are discussed in the category "Salivary carcinoma not otherwise specified (NOS) and emerging entities". New defining genomic alterations have been characterized in many salivary gland tumors. In particular, they include gene fusions, which have shown to be tightly tumor-type specific, and thus valuable for use in diagnostically challenging cases. The recurrent molecular alterations were included in the definition of mucoepidermoid carcinoma, adenoid cystic carcinoma, secretory carcinoma, polymorphous adenocarcinoma, hyalinizing clear cell carcinoma, mucinous adenocarcinoma, and microsecretory adenocarcinoma.

HMGA2-WIF1 Rearrangements Characterize a Distinctive Subset of Salivary Pleomorphic Adenomas With Prominent Trabecular (Canalicular Adenoma-like) Morphology

Most of salivary gland neoplasms (benign and malignant) are characterized by recurrent gene fusions. Pleomorphic adenoma (PA), the most frequent salivary gland tumor, is driven by chromosomal rearrangements involving PLAG1 mapped to 8q12 and HMGA2 mapped to 12q13-15 in most cases. Multiple fusion partners have been identified including CTNNB1, FGFR1, LIFR, CHCHD7 and TCEA for PLAG1 fusions and NFIB, WIF1 and FHIT for HMGA2 fusions. To date, no data exist on the morphology of the few reported HMGA2-WIF1-rearranged PAs. We present 28 major salivary gland adenomas displaying distinctive trabecular and canalicular morphology associated with recurrent genotype. Patients were 15 females and 13 males aged 43 to 87 (median: 65). All tumors originated from the parotid. Their size range was 1 to 4 cm (mean: 2.3). Histologically, all tumors showed elongated or columnar cells arranged into bilayered to multilayered communicating and branching strands and trabeculae in a manner similar to canalicular adenoma of minor salivary glands or trabecular myoepithelioma with variable solid confluent intercalated duct-like areas. Fifteen tumors were exclusively canalicular/trabecular while 13 had intermingled or well-demarcated conventional (chondromyxoid) PA component comprising 5 to >50% of the tumor. The monomorphic areas expressed uniformly CK7 (28/28), vimentin (21/21), S100 (24/24), SOX10 (16/17) and variably p63 (8/21) and mammaglobin (6/16) but were negative with p40 (0/24), smooth muscle actin (0/24) and MUC4 (0/16). Targeted RNA sequencing revealed HMGA2 fusions in 14/16 (87%) assessable cases. Fusion partner was WIF1 (12), RPSAP52 (1) and HELB (1). Separate testing of the 2 components in 1 hybrid tumor showed same HMGA2/WIF1 fusion. HMGA2 immunohistochemistry was homogeneously positive in all cases including the 2 fusion-negative cases. A control cohort of 12 genuine canalicular adenomas revealed no HMGA2 fusions (0/4) and lacked HMGA2 immunoreactivity (0/12). This study highlights a distinctive variant in the spectrum of PA characterized by prominent trabecular and canalicular adenoma-like morphology. Our data confirm that canalicular adenomas in major salivary glands (either monomorphic or part of hybrid tumors) are distinct from canalicular adenoma of minor salivary glands. Their uniform genotype irrespective of presence or absence of a conventional PA component argues for classifying those tumors lacking a conventional PA component as "monomorphic variants of PA" rather than canalicular/basal cell adenomas, intercalated duct adenoma, trabecular myoepithelioma or true hybrid tumors.

Xp11.2 Translocation Renal Cell Carcinoma With TFE3 Rearrangement: Distinct Morphological Features and Prognosis With Different Fusion Partners

Background

Renal cell carcinoma (RCC) associated with Xp11.2 translocation/TFE3 gene fusion is a rare and new subtype of RCC and was classified by the WHO in 2004. Since then, multiple 5′ fusion partners for TFE3 have been reported; however, the impact of individual fusion variant on specific clinicopathologic features of Xp11.2 RCCs has not been well defined.

Methods

Four Xp11.2 translocation RCCs were identified by morphological, immunostaining, and fluorescence in situ hybridization (FISH) assays from 200 patients who attended Guangdong General Hospital between January 2017 and January 2020. All these four cases were further analyzed by RNA sequencing to explore their TFE3 gene fusion partners. The clinicopathologic features, including clinical manifestations, pathological findings, treatment strategies, clinical outcomes, and follow-up information on Xp11.2 translocation RCCs, were recorded and evaluated.

Results

These four cases affected one male and three females. The median age was 13 years at the time of diagnosis (range = 4–20 years). All the examined tumors were unilateral and unifocal. The largest diameter of these tumors ranged from 2.0 to 10.0 cm, and the average was 5.55 cm. Regional lymph node or distant metastasis developed in two patients. Three cases demonstrated known fusions: ASPCR1–TFE3 (two cases) and PRCC–TFE3 (one case). However, one case showed an unreported VCP–TFE3 fusion gene in Xp11.2 translocation RCCs. Immunohistochemistry results revealed tumor cells diffusely positive for TFE3, but have no consistency in other markers. Moreover, there were different clinical prognoses among the different variant TFE3 rearrangements; RCC patients with VCP–TFE3 translocation had worse prognosis compared to those with other fusion types. Follow-up were available for all the patients and ranged from 3 to 36 months. Three patients were without evidence of disease progression, while that with VCP–TFE3 fusion died of the disease 3 months after the diagnosis.

Conclusion

In conclusion, our data expand the list of TFE3 gene fusion partners and the clinicopathologic features of Xp11.2 RCCs with specific TFE3 gene fusions. We identified a novel VCP–TFE3 fusion in Xp11.2 translocation RCCs for the first time, which has unique morphology and worse prognosis than those with other variant TFE3 rearrangements. Integration of morphological, immunohistochemical, and molecular methods is often necessary for the precise diagnosis and optimal clinical management of malignant tumors.

An Overview on the Histogenesis and Morphogenesis of Salivary Gland Neoplasms and Evolving Diagnostic Approaches

Simple Summary

Diagnosing salivary gland neoplasms (SGN) remain a challenge, given their underlying biological nature and overlapping features. Evolving techniques in molecular pathology have uncovered genetic mutations resulting in these tumors. This review delves into the molecular etiopatho-genesis of SGN, highlighting advanced diagnostic protocols that may facilitate the identification and therapy of a variety of SGN.

Abstract

Salivary gland neoplasms (SGN) remain a diagnostic dilemma due to their heterogenic complex behavior. Their diverse histomorphological appearance is attributed to the underlying cellular mechanisms and differentiation into various histopathological subtypes with overlapping fea-tures. Diagnostic tools such as fine needle aspiration biopsy, computerized tomography, magnetic resonance imaging, and positron emission tomography help evaluate the structure and assess the staging of SGN. Advances in molecular pathology have uncovered genetic patterns and oncogenes by immunohistochemistry, fluorescent in situ hybridization, and next–generation sequencing, that may potentially contribute to innovating diagnostic approaches in identifying various SGN. Surgical resection is the principal treatment for most SGN. Other modalities such as radiotherapy, chemotherapy, targeted therapy (agents like tyrosine kinase inhibitors, monoclonal antibodies, and proteasome inhibitors), and potential hormone therapy may be applied, depending on the clinical behaviors, histopathologic grading, tumor stage and location, and the extent of tissue invasion. This review delves into the molecular pathways of salivary gland tumorigenesis, highlighting recent diagnostic protocols that may facilitate the identification and management of SGN.

Expression of Transcription Factor CREM in Human Tissues

Cyclic AMP element modulator (CREM) is a transcription factor best known for its intricate involvement in spermatogenesis. The CREM gene encodes for multiple protein isoforms, which can enhance or repress transcription of target genes. Recent studies have identified fusion genes, with CREM as a partner gene in many neoplastic diseases. EWSR1-CREM fusion genes have been found in several mesenchymal tumors and in salivary gland carcinoma. These genes encode fusion proteins that include the C-terminal DNA-binding domain of CREM. We used a transcriptomic approach and immunohistochemistry to study the expression of CREM isoforms that include DNA-binding domains across human tissues. We found that CREM protein is widely expressed in almost all normal human tissues. A transcriptomic analysis of normal tissues and cancer showed that transcription of CREM can be altered in tumors, suggesting that also wild-type CREM may be involved in cancer biology. The wide expression of CREM protein in normal human tissues and cancer may limit the utility of immunohistochemistry for identification of tumors with CREM fusions:

ETV6-NTRK3 translocation-associated low-grade mucinous bronchial adenocarcinoma: A novel bronchial salivary gland-type non-small cell lung cancer subtype

INTRODUCTION

NTRK fusion genes have been found in several solid tumors, among which NSCLC and sarcoma. Novel NTRK translocation-related tumors are still being discovered.

METHODS

We report a 49-year-old patient with a mass in the left lower lung lobe that was resected. This specimen was analyzed and sequenced using targeted DNA next generation sequencing (NGS) and anchored-multiplex-PCR (AMP) targeted RNA NGS.

RESULTS

On pathological evaluation, a peribronchial mucinous neoplasm with a unique morphology was found. RNA NGS analysis showed anETV6-NTRK3 translocation in a low-grade mucinous bronchial adenocarcinoma.

CONCLUSIONS

This entity represents a novel subtype of non-small cell lung cancer, which we would like to term 'ETV6-NTRK3 translocation-associated low-grade mucinous bronchial adenocarcinoma'.