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.

Molecularly defined sinonasal malignancies: an overview with focus on the current WHO classification and recently described provisional entities.

Classification of tumors of the head and neck has evolved in recent decades including a widespread application of molecular testing in tumors of the sinonasal tract, salivary glands, and soft tissues with a predilection for the head and neck. The availability of new molecular techniques has allowed for the definition of multiple novel tumor types unique to head and neck sites. Moreover, an expanding spectrum of immunohistochemical markers specific to genetic alterations facilitates rapid identification of diagnostic molecular abnormalities. As such, it is currently possible for head and neck pathologists to benefit from a molecularly defined tumor classification while making diagnoses that are still based largely on histopathology and immunohistochemistry. This review covers the principal molecular alterations in sinonasal malignancies, such as alterations in DEK, AFF2, NUTM1, IDH1-2, and SWI/SNF genes in particular, that are important from a practical standpoint for diagnosis, prognosis, and prediction of response to treatment.

Predictive value of tumor budding in head and neck squamous cell carcinoma: an update.

Head and neck squamous cell carcinoma forms an anatomically and functionally complex group of malignancies. The significant local aggressiveness and frequent regional relapses motivate ongoing research to identify more reliable and sensitive prognostic and predictive biomarkers. One emerging area of cancer biology is the evaluation of tumor budding at the advancing invasive front of various types of epithelial cancers. Recent studies suggest that tumor budding is a relatively common phenomenon in cancer progression and that it may have important prognostic implications for patients due to its potential to provide valuable insights into the biology and clinical behavior of head and neck cancer. In this review, we aim to provide information about tumor budding in head and neck squamous cell carcinoma. Thus, we hope to shed light on the complex biology of these malignancies, as well as aiding diagnostic, classification, and better characterization and thereby, looking for new avenues for improving patient outcomes.

Salivary Gland Secretory Carcinoma: Clinicopathologic and Genetic Characteristics of 215 Cases and Proposal for a Grading System.

Salivary gland secretory carcinoma (SC), previously mammary analog SC, is a low-grade malignancy characterized by well-defined morphology and an immunohistochemical and genetic profile identical to SC of the breast. Translocation t(12;15)(p13;q25) resulting in the ETV6 :: NTRK3 gene fusion is a characteristic feature of SC along with S100 protein and mammaglobin immunopositivity. The spectrum of genetic alterations for SC continues to evolve. The aim of this retrospective study was to collect data of salivary gland SCs and to correlate their histologic, immunohistochemical, and molecular genetic data with clinical behavior and long-term follow-up. In this large retrospective study, we aimed to establish a histologic grading scheme and scoring system. A total of 215 cases of salivary gland SCs diagnosed between 1994 and 2021 were obtained from the tumor registries of the authors. Eighty cases were originally diagnosed as something other than SC, most frequently acinic cell carcinoma. Lymph node metastases were identified in 17.1% (20/117 cases with available data), with distant metastasis in 5.1% (6/117). Disease recurrence was seen in 15% (n=17/113 cases with available data). The molecular genetic profile showed ETV6 :: NTRK3 gene fusion in 95.4%, including 1 case with a dual fusion of ETV6 :: NTRK3 and MYB :: SMR3B . Less frequent fusion transcripts included ETV6 :: RET (n=12) and VIM :: RET (n=1). A 3-tiered grading scheme using 6 pathologic parameters (prevailing architecture, pleomorphism, tumor necrosis, perineural invasion (PNI), lymphovascular invasion (LVI), and mitotic count and/or Ki-67 labeling index) was applied. Grade 1 histology was observed in 44.7% (n=96), grade 2 in 41.9% (n=90), and grade 3 in 13.5% (n=29) of cases. Compared with low-grade and intermediate-grade SC, high-grade tumors were associated with a solid architecture, more prominent hyalinization, infiltrative tumor borders, nuclear pleomorphism, presence of PNI and/or LVI, and Ki-67 proliferative index >30%. High-grade transformation, a subset of grade 2 or 3 tumors, seen in 8.8% (n=19), was defined as an abrupt transformation of conventional SC into high-grade morphology, sheet-like growth, and a tumor lacking distinctive features of SC. Both overall survival and disease-free survival (5 and 10 y) were negatively affected by tumor grade, stage, and TNM status (each P <0.0001). SC is a low-grade malignancy with predominantly solid-microcystic growth patterns, driven by a gene fusion, most commonly ETV6 :: NTRK3 . There is a low risk for local recurrence and a good overall long-term survival, with a low risk for distant metastasis but a higher risk for locoregional lymph node metastasis. The presence of tumor necrosis, hyalinization, PNI and/or LVI, and positive resection margins correlate with higher tumor grade, less favorable prognosis, and increased mortality. The statistical results allowed us to design a 3-tiered grading system for salivary SC.

Comprehensive Molecular Profiling of Sinonasal Teratocarcinosarcoma Highlights Recurrent SMARCA4 Inactivation and CTNNB1 Mutations.

Sinonasal teratocarcinosarcoma (TCS) is a rare tumor defined by intermixed neuroepithelial, mesenchymal, and epithelial elements. While its etiology was historically ambiguous, we recently reported frequent SMARCA4 loss by immunohistochemistry, suggesting that TCS might be related to SMARCA4-deficient sinonasal carcinomas. However, other molecular alterations including CTNNB1 mutation have been reported in TCS, and its full genetic underpinnings are unclear. Here, we performed the first comprehensive molecular analysis of sinonasal TCS to better understand its pathogenesis and classification. We collected 30 TCS including 22 cases from our initial study. Immunohistochemical loss of SMARCA4 was seen in 22 cases (73%), with total loss in 18 cases (60%). ß-catenin showed nuclear localization in 14 cases (64%) of the subset tested. We selected 17 TCS for next-generation sequencing with enrichment for partial or intact SMARCA4 immunoexpression. We identified inactivating SMARCA4 mutations in 11 cases (65%) and activating CTNNB1 mutations in 6 cases (35%), including 5 cases with both. Of 5 cases that lacked SMARCA4 or CTNNB1 mutation, 2 harbored other SWI/SNF complex and Wnt pathway alterations, including 1 with SMARCB1 inactivation and 1 with concomitant APC and ARID1A mutations, and 3 had other findings, including DICER1 hotspot mutation. These findings confirm that SMARCA4 inactivation is the dominant genetic event in sinonasal TCS with frequent simultaneous CTNNB1 mutations. They further underscore a possible relationship between TCS and sinonasal carcinomas with neuroendocrine/neuroectodermal differentiation. However, while SMARCA4 and ß-catenin immunohistochemistry may help confirm a challenging diagnosis, TCS should not be regarded as a molecularly defined entity.

Clear Cell Neoplasms of Salivary Glands: A Diagnostic Challenge.

This review focuses on the heterogenous group of clear cell neoplasms of salivary glands and attempts to identify major differential diagnostic features. Within the head and neck region, clear cells are found most commonly in salivary gland tumors, but may also be seen in tumors of squamous or odontogenic epithelial origin, primary or metastatic carcinomas, benign or malignant melanocytic lesions, or benign or malignant mesenchymal tumors. Clear cells occur fairly commonly among a wide variety of salivary gland neoplasms, but mostly they constitute only a minor component of the tumor cell population. Clear cells represent a major diagnostic feature in two salivary gland neoplasms, epithelial-myoepithelial carcinoma and hyalinizing clear cell carcinoma. In addition, salivary gland neoplasms composed predominantly of clear cells could also include clear cell variants of other salivary neoplasms, such as mucoepidermoid carcinoma and myoepithelial carcinoma, but their tumor type-specific histologic features may only be available in limited nonclear cell areas of the tumor. Diagnosing predominantly clear cell salivary gland tumors is difficult because the immunoprofiles and morphologic features may overlap and the same tumor entity may also have a wide range of other histologic presentations. Many salivary gland tumors are characterized by tumor type-specific genomic alterations, particularly gene fusions of the ETV6 gene in secretory carcinoma, the MYB and MYBL1 genes in adenoid cystic carcinoma, the MAML2 gene in mucoepidermoid carcinoma, the EWSR1 gene in hyalinizing clear cell carcinoma, and others. Thus, along with conventional histopathologic examination and immunoprofiling, molecular and genetic tests may be important in the diagnosis of salivary gland clear cell tumors by demonstrating genetic alterations specific to them.

Development of head and neck pathology in Europe.

This review gives a brief history of the development of head and neck pathology in Europe from a humble beginning in the 1930s to the explosive activities the last 15 years. During the decades before the introduction of immunohistochemistry in the 1980s, head and neck pathology grew as a subspeciality in many European countries. In the late 1940s, the Institute of Laryngology and Otology with its own pathology laboratory was founded in London, and in 1964 the World Health Organization (WHO) International Reference Centre for the Histological Classification of Salivary Tumours was established at the Bland-Sutton Institute of Pathology, also in London. International collaboration, and very much so in Europe, led to the publication of the first WHO Classification of Salivary Gland Tumours in 1972. In the 1960s, a salivary gland register was organised in Hamburg and in Cologne the microlaryngoscopy was invented enabling microscopic endoscopic examination and rather shortly afterwards a carbon dioxide laser attached to the microscope became established and laryngeal lesions could be treated by laser vaporisation. During the last three decades, the use of immunohistochemistry supplemented with cytogenetic and refined molecular techniques has greatly facilitated the pathological diagnostics of head and neck lesions and has had a huge impact on research. Collaboration between different European centres has drastically increased partly due to establishment of scientific societies such as the Head and Neck Working Group (HNWG) within the European Society of Pathology and the International Head and Neck Scientific Group (IHNSG). A very large number of European pathologists have contributed to the 2nd, 3rd and 4th WHO books, and are involved in the upcoming 5th edition. Accredited educational meetings and courses are nowadays regularly arranged in Europe. Numerous textbooks on head and neck pathology have been written and edited by European pathologists. The increased collaboration has created larger series of tumours for research and new entities, mainly defined by their genetic abnormalities, are continuously emerging from Europe, particularly regarding salivary gland neoplasms and "undifferentiated" sinonasal tumours. These findings have led to a better and more precise classification and open the possibilities for new treatment strategies.

High-grade Transformation/Dedifferentiation in Salivary Gland Carcinomas: Occurrence Across Subtypes and Clinical Significance.

High-grade transformation (HGT) or dedifferentiation has been described in a variety of salivary gland carcinomas, including acinic cell carcinoma, secretory carcinoma, adenoid cystic carcinoma, epithelial-myoepithelial carcinoma, polymorphous adenocarcinoma, low-grade mucoepidermoid carcinoma, and hyalinizing clear cell carcinoma. High-grade (HG) transformed tumors are composed of a conventional low-grade component characterized by specific microscopic and immunohistochemical features for the given entity, intermingled with or juxtaposed to areas of HG morphology. This is usually either poorly differentiated adenocarcinoma, carcinoma not otherwise specified, or undifferentiated carcinoma, in which the original line of differentiation is lost. The HG component is composed of solid nests of anaplastic cells with large vesicular pleomorphic nuclei, prominent nucleoli, and abundant cytoplasm. Frequent mitoses and extensive necrosis may be present. The Ki-67 labeling index is consistently higher in the HG component. The molecular genetic mechanisms responsible for HGT of salivary gland carcinomas are largely unknown, though p53 inactivation and human epidermal growth factor receptor 2 overexpression and/or gene amplification have been demonstrated in the HG component in a few examples, the frequency varies for each histologic type. Salivary gland carcinomas with HGT are more aggressive than conventional carcinomas, with a higher local recurrence rate and a poorer prognosis. They have a high propensity for cervical lymph node metastasis suggesting a need for a wider resection and neck dissection. HGT of salivary gland carcinoma can occur either at initial presentation or less commonly at the time of recurrence, sometimes following postoperative radiotherapy. The potential for HGT in almost any type of salivary gland carcinoma warrants a thorough sampling of all salivary gland malignancies to prevent oversight of a HG component.

Expanding the Molecular Spectrum of Secretory Carcinoma of Salivary Glands With a Novel VIM-RET Fusion.

BACKGROUND: Secretory carcinoma (SC), originally described as mammary analogue SC, is a predominantly low-grade salivary gland neoplasm characterized by a recurrent t(12;15)(p13;q25) translocation, resulting in ETV6-NTRK3 gene fusion. Recently, alternative ETV6-RET, ETV6-MAML3, and ETV6-MET fusions have been found in a subset of SCs lacking the classic ETV6-NTRK3 fusion transcript, but still harboring ETV6 gene rearrangements. DESIGN: Forty-nine cases of SC revealing typical histomorphology and immunoprofile were analyzed by next-generation sequencing using the FusionPlex Solid Tumor kit (ArcherDX). All 49 cases of SC were also tested for ETV6, RET, and NTRK3 break by fluorescence in situ hybridization and for the common ETV6-NTRK3 fusions using reverse transcription polymerase chain reaction. RESULTS: Of the 49 cases studied, 37 (76%) occurred in the parotid gland, 7 (14%) in the submandibular gland, 2 (4%) in the minor salivary glands, and 1 (2%) each in the nasal mucosa, facial skin, and thyroid gland. SCs were diagnosed more frequently in males (27/49 cases; 55%). Patients' age at diagnosis varied from 15 to 80 years, with a mean age of 49.9 years. By molecular analysis, 40 cases (82%) presented the classic ETV6-NTRK3 fusion, whereas 9 cases (18%) revealed an alternate fusion. Of the 9 cases negative for the ETV6-NTRK3 fusion, 8 cases presented with ETV6-RET fusion. In the 1 remaining case in the parotid gland, next-generation sequencing analysis identified a novel VIM-RET fusion transcript. In addition, the analysis indicated that 1 recurrent high-grade case in the submandibular gland was positive for both ETV6-NTRK3 and MYB-SMR3B fusion transcripts. CONCLUSIONS: A novel finding in our study was the discovery of a VIM-RET fusion in 1 patient with SC of the parotid gland who could possibly benefit from RET-targeted therapy. In addition, 1 recurrent high-grade case was shown to harbor 2 different fusions, namely, ETV6-NTRK3 and MYB-SMR3B. The expanded molecular spectrum provides a novel insight into SC oncogenesis and carries important implications for molecular diagnostics, as this is the first SC-associated translocation with a non-ETV6 5' fusion partner. This finding further expands the definition of SC while carrying implications for selecting the appropriate targeted therapy.

MYB-NFIB gene fusions identified in archival adenoid cystic carcinoma tissue employing NanoString analysis: an exploratory study.

BACKGROUND: Adenoid cystic carcinoma (ACC) is a slow growing salivary gland malignancy that is molecularly characterized by t(6:9)(q22-23;p23-24) translocations which predominantly result in MYB-NFIB gene fusions in nearly half of tumours. Detection of MYB-NFIB transcripts is typically performed with fresh ACC tissue using conventional RT-PCR fragment analysis or FISH techniques, which are prone to failure when only archival formalin fixed paraffin embedded (FFPE) tissue is available. The purpose of this pilot study was to evaluate the utility of NanoString probe technology for the detection of MYB-NFIB transcripts in archival ACC tissue. METHODS: A NanoString probeset panel was designed targeting the junctions of three currently annotated MYB-NFIB fusion genes as well as 5'/3' MYB probesets designed to detect MYB gene expression imbalance. RNA isolated from twenty-five archival ACC specimens was profiled and analyzed. RT-qPCR and sequencing were performed to confirm NanoString results. MYB protein expression was analyzed by immunohistochemistry. RESULTS: Of the 25 samples analyzed, 11/25 (44%) expressed a high degree of MYB 5'/3' imbalance and five of these samples were positive for at least one specific MYB-NFIB variant in our panel. MYB-NFIB variant detection on NanoString analysis was confirmed by direct cDNA sequencing. No clinical correlations were found to be associated with MYB fusion status. CONCLUSION: We conclude that the application of NanoString digital probe counting technology is well suited for the detection and quantification of MYB-NFIB fusion transcripts in archival ACC specimens.

Molecular Profiling of Mammary Analog Secretory Carcinoma Revealed a Subset of Tumors Harboring a Novel ETV6-RET Translocation: Report of 10 Cases.

ETV6 gene abnormalities are well described in tumor pathology. Many fusion partners of ETV6 have been reported in a variety of epithelial, mesenchymal, and hematological malignancies. In salivary gland tumor pathology, however, the ETV6-NTRK3 translocation is specific for (mammary analog) secretory carcinoma, and has not been documented in any other salivary tumor type. The present study comprised a clinical, histologic, and molecular analysis of 10 cases of secretory carcinoma, with typical morphology and immunoprofile harboring a novel ETV6-RET translocation.

The Role of Molecular Testing in the Differential Diagnosis of Salivary Gland Carcinomas.

Salivary gland neoplasms are a morphologically heterogenous group of lesions that are often diagnostically challenging. In recent years, considerable progress in salivary gland taxonomy has been reached by the discovery of tumor type-specific fusion oncogenes generated by chromosome translocations. This review describes the clinicopathologic features of a selected group of salivary gland carcinomas with a focus on their distinctive genomic characteristics. Mammary analog secretory carcinoma is a recently described entity characterized by a t(12;15)(p13;q25) translocation resulting in an ETV6-NTRK3 fusion. Hyalinizing clear cell carcinoma is a low-grade tumor with infrequent nodal and distant metastasis, recently shown to harbor an EWSR1-ATF1 gene fusion. The CRTC1-MAML2 fusion gene resulting from a t(11;19)(q21;p13) translocation, is now known to be a feature of both low-grade and high-grade mucoepidermoid carcinomas associated with improved survival. A t(6;9)(q22-23;p23-34) translocation resulting in a MYB-NFIB gene fusion has been identified in the majority of adenoid cystic carcinomas. Polymorphous (low-grade) adenocarcinoma and cribriform adenocarcinoma of (minor) salivary gland origin are related entities with partly differing clinicopathologic and genomic profiles; they are the subject of an ongoing taxonomic debate. Polymorphous (low-grade) adenocarcinomas are characterized by hot spot point E710D mutations in the PRKD1 gene, whereas cribriform adenocarcinoma of (minor) salivary glands origin are characterized by translocations involving the PRKD1-3 genes. Salivary duct carcinoma (SDC) is a high-grade adenocarcinoma with morphologic and molecular features akin to invasive ductal carcinoma of the breast, including HER2 gene amplification, mutations of TP53, PIK3CA, and HRAS and loss or mutation of PTEN. Notably, a recurrent NCOA4-RET fusion has also been found in SDC. A subset of SDC with apocrine morphology is associated with overexpression of androgen receptors. As these genetic aberrations are recurrent they serve as powerful diagnostic tools in salivary gland tumor diagnosis, and therefore also in refinement of salivary gland cancer classification. Moreover, they are promising as prognostic biomarkers and targets of therapy.

SMARCB1 (INI-1)-deficient Sinonasal Carcinoma: A Series of 39 Cases Expanding the Morphologic and Clinicopathologic Spectrum of a Recently Described Entity.

To more fully characterize the clinical and pathologic spectrum of a recently described tumor entity of the sinonasal tract characterized by loss of nuclear expression of SMARCB1 (INI1), we analyzed 39 SMARCB1-deficient sinonasal carcinomas collected from multiple medical centers. The tumors affected 23 males and 16 females with an age range of 19 to 89 years (median, 52). All patients presented with locally advanced disease (T3, n=5; T4, n=27) involving the sinuses (mainly ethmoid) with variable involvement of the nasal cavity. Thirty patients received surgery and/or radiochemotherapy with curative intent. At last follow-up, 56% of patients died of disease 0 to 102 months after diagnosis (median, 15), 2 were alive with disease, and 1 died of an unrelated cause. Only 9 patients (30%) were alive without disease at last follow-up (range, 11 to 115 mo; median, 26). The original diagnosis of retrospectively identified cases was most often sinonasal undifferentiated carcinoma (n=14) and nonkeratinizing/basaloid squamous cell carcinoma (n=5). Histologically, most tumors displayed either a predominantly basaloid (61%) or plasmacytoid/rhabdoid morphology (36%). The plasmacytoid/rhabdoid form consisted of sheets of tumor cells with abundant, eccentrically placed eosinophilic cytoplasm, whereas similar cells were typically rare and singly distributed in the basaloid variant. Glandular differentiation was seen in a few tumors. None of the cases showed squamous differentiation or surface dysplasia. By immunohistochemistry, the tumors were positive for pancytokeratin (97%), CK5 (64%), p63 (55%), and CK7 (48%); and they were negative for NUT (0%). Epstein-Barr virus and high-risk human papillomavirus was not detected by in situ hybridization. Immunohistochemical loss of SMARCB1 (INI1) expression was confirmed for all 39 tumors. Investigation of other proteins in the SWI/SNF complex revealed co-loss of SMARCA2 in 4 cases, but none were SMARCA4 deficient or ARID1A deficient. Of 27 tumors with SMARCB1 fluorescence in situ hybridization analysis, 14 showed homozygous (biallelic) deletions and 7 showed heterozygous (monoallelic) deletions. SMARCB1-deficient sinonasal carcinoma represents an emerging poorly differentiated/undifferentiated sinonasal carcinoma that (1) cannot be better classified as another specific tumor type, (2) has consistent histopathologic findings (albeit with some variability) with varying proportions of plasmacytoid/rhabdoid cells, and (3) demonstrates an aggressive clinical course. This entity should be considered in any difficult-to-classify sinonasal carcinoma, as correct diagnosis will be mandatory for optimizing therapy and for further delineation of this likely underdiagnosed disease.

Mammary Analogue Secretory Carcinoma of Salivary Glands: Molecular Analysis of 25 ETV6 Gene Rearranged Tumors With Lack of Detection of Classical ETV6-NTRK3 Fusion Transcript by Standard RT-PCR: Report of 4 Cases Harboring ETV6-X Gene Fusion.

ETV6 gene abnormalities are well described in tumor pathology. Many fusion partners of ETV6 have been reported in a variety of epithelial and hematological malignancies. In salivary gland tumor pathology, however, the ETV6-NTRK3 translocation is specific for mammary analogue secretory carcinoma (MASC), and has not been documented in any other salivary tumor type. The present study comprised a clinical and molecular analysis of 25 cases morphologically and immunohistochemically typical of MASC. They all also displayed the ETV6 rearrangement as visualized by fluorescent in situ hybridization but lacked the classical ETV6-NTRK3 fusion transcript by standard reverse-transcriptase-polymerase chain reaction. In 4 cases, the classical fusion transcript was found by more sensitive, nested reverse-transcription-polymerase chain reaction. Five other cases harbored atypical fusion transcripts as detected by both standard and nested reverse-transcription-polymerase chain reaction. In addition, fluorescent in situ hybridization with an NTRK3 break-apart probe was also performed; rearrangement of NTRK3 gene was detected in 16 of 25 cases. In 3 other cases, the tissue was not analyzable, and in 2 further cases analysis could not be performed because of a lack of appropriate tissue material. Finally, in the 4 remaining cases whose profile was NTRK3 split-negative and ETV6 split-positive, unknown (non-NTRK) genes appeared to fuse with ETV6 (ETV6-X fusion). In looking for possible fusion partners, analysis of rearrangement of other kinase genes known to fuse with ETV6 was also performed, but without positive results. Although numbers were small, correlating the clinico-pathologic features of the 4 ETV6-X fusion tumors and 5 MASC cases with atypical fusion transcripts raises the possibility of that they may behave more aggressively.

Clear cell myoepithelial carcinoma of salivary glands showing EWSR1 rearrangement: molecular analysis of 94 salivary gland carcinomas with prominent clear cell component.

This study examines the presence of the EWSR1 rearrangement in a variety of clear cell salivary gland carcinomas with myoepithelial differentiation. A total of 94 salivary gland carcinomas with a prominent clear cell component included 51 cases of clear cell myoepithelial carcinomas de novo (CCMC), 21 cases of CCMCs ex pleomorphic adenoma (CCMCexPA), 11 cases of epithelial-myoepithelial carcinoma (EMC), 6 cases of EMC with solid clear cell overgrowth, and 5 cases of hyalinizing clear cell carcinoma of minor salivary glands. In addition, 10 cases of myoepithelial carcinomas devoid of clear cell change and 12 cases of benign myoepithelioma were included as well. All the tumors in this spectrum were reviewed, reclassified, and tested by fluorescence in situ hybridization (FISH) for the EWSR1 rearrangement using the Probe Vysis EWSR1 Break Apart FISH Probe Kit. The EWSR1 rearrangement was detected in 20 of 51 (39%) cases of CCMC, in 5 of 21 (24%) cases of CCMCexPA, in 1 of 11 (9%) cases of EMC, and in 4 of 5 (80%) cases of hyalinizing clear cell carcinoma. The 25 EWSR1-rearranged CCMCs and CCMCexPAs shared similar histomorphology. They were arranged in nodules composed of compact nests of large polyhedral cells with abundant clear cytoplasm. Necrosis, areas of squamous metaplasia, and hyalinization were frequent features. Immunohistochemically, the tumors expressed p63 (96%), cytokeratin CK14 (96%), and S100 protein (88%). MIB1 index varied from 10% to 100%, with most cases in the 20% to 40% range. Clinical follow-up information was available in 21 cases (84%) and ranged from 3 months to 15 years (mean 5.2 y); 4 patients were lost to follow-up. Ten patients are alive with no evidence of recurrent or metastatic disease in the follow-up period from 3 months to 15 years (mean 5 y), 3 patients are alive with recurrent and metastatic disease, and 8 died of disseminated cancer 9 months to 16 years after diagnosis (mean 6 y). Lymph node metastasis appeared in 5 patients within 5 months to 4 years after diagnosis (mean 22 mo), distant metastases were noted in 7 patients with invasion of orbit (2 cases), and in 1 case each metastasis to the neck soft tissues, liver, lungs, mediastinum, and thoracic vertebra was noted. We describe for the first time EWSR1 gene rearrangement in a subset of myoepithelial carcinomas arising in minor and major salivary glands. The EWSR1-rearranged CCMC represents a distinctive aggressive variant composed predominantly of clear cells with frequent necrosis. Most EWSR1-rearranged CCMCs of salivary glands are characterized by poor clinical outcomes.

Recent advances in the diagnostic pathology of salivary carcinomas.

This review concentrates on the most important developments since the WHO classification of 2005. In particular, the identification of specific translocations is revolutionising the way salivary tumours are considered and will have a major impact on future diagnostic practice. This is true so far in four malignancies: mammary analogue secretory, mucoepidermoid, adenoid cystic and hyalinising clear cell carcinomas. In each, the gene rearrangement is found in 80 % or more of cases. Two 2014 publications have added further possible candidates with molecular abnormalities to the list (cribriform adenocarcinoma of the tongue and minor salivary glands and epithelial-myoepithelial carcinoma), but these findings have yet to be confirmed by other investigators. The advances in molecular pathology have also allowed re-evaluation of the morphology; for example, it is now realised that the histological spectrum of hyalinising clear cell carcinoma includes intracellular mucin in over half of cases, as well as tumours with only scanty clear cells. In a separate development, it is now proposed that salivary duct carcinoma can be subdivided along molecular lines, in ways analogous to breast cancer, suggesting new therapeutic prospects in an otherwise highly aggressive malignancy.

Mammary analogue secretory carcinoma of salivary glands with high-grade transformation: report of 3 cases with the ETV6-NTRK3 gene fusion and analysis of TP53, ß-catenin, EGFR, and CCND1 genes.

Mammary analogue secretory carcinoma of salivary gland origin (MASC) is a recently described tumor resembling secretory carcinoma of the breast characterized by strong S-100 protein, mammaglobin, and vimentin immunoexpression and which harbors a t(12;15) (p13;q25) translocation resulting in ETV6-NTRK3 fusion product. Histologically, conventional MASC displays bland histomorphology and a lobulated growth pattern and is often composed of microcystic, tubular, and solid structures with abundant eosinophilic homogenous or bubbly secretions. Colloid-like secretory material stains positively for periodic acid-Schiff with and without diastase as well as for Alcian Blue. We present for the first time, 3 patients with MASC of the parotid gland in which high-grade (HG) transformation developed in each case characterized by an accelerated clinical course and poor outcome. The HG component revealed strong membrane staining for EGFR and ß-catenin, cytoplasmic/nuclear staining for S-100 protein, and nuclear staining for cyclin-D1, whereas HER-2/neu was absent. Analysis for the presence of the ETV6-NTRK3 fusion transcript revealed positivity in both HG and low-grade component of MASC in 2 of the 3 studied cases. The tumor in case 2 was negative in both its elements for the t(12;15) translocation, but ETV6 gene rearrangement was detected in both components in all 3 cases. Analysis of TP53 and CTNNB1 gene mutations in the HG component of MASCs as well as detection of copy number aberration of EGFR and CCND1 gene did not harbor any abnormalities. All 3 patients with HG-transformed MASC died of disseminated disease within 2 to 6 years after diagnosis. Recognizing HG-transformed MASC and testing for ETV6 rearrangement may be of potential value in patient treatment, because the presence of the ETV6-NTRK3 translocation may represent a therapeutic target in MASC.

CRTC1-MAML2 and CRTC3-MAML2 fusions were not detected in metaplastic Warthin tumor and metaplastic pleomorphic adenoma of salivary glands.

The recurrent translocations t(11;19) and t(11;15) resulting in CRTC1-MAML2 or CRTC3-MAML2 fusion oncogenes, respectively, are identified in a large proportion of mucoepidermoid carcinomas (MECs) of the salivary gland and have impact on prognosis. However, there are conflicting data on the specificity of this translocation, in particular, on its putative occurrence in Warthin tumor (WT) of the parotid gland as reported in few previous cases. It was speculated that extensive squamous metaplasia could explain the presence of t(11;19) translocation in a subset of WTs. We evaluated 76 salivary gland tumors, including 16 cases of metaplastic WT and 8 cases of pleomorphic adenoma (PA) with squamous and/or mucinous metaplasia, extensive enough morphologically to mimic MEC. Detection of CRTC1-MAML2 and CRTC3-MAML2 fusion transcripts and MAML2 gene break was performed using nested reverse transcription-polymerase chain reaction and fluorescence in situ hybridization (FISH), respectively. None of 16 analyzed metaplastic WTs showed positivity for fusion transcripts CRTC1-MAML2 or CRTC3-MAML2, and none showed rearrangement of the MAML2 gene by FISH. Similarly, we did not detect these transcripts or break of MAML2 gene in any case of PA with extensive squamous/mucinous metaplasia. For comparison, 40 cases of low-grade MEC were also evaluated. CRTC1-MAML2 and CRTC3-MAML2 fusion transcripts were detected in 17 and 5 cases, respectively. The FISH method using break-apart probe demonstrated the MAML2 gene rearrangement in 25 cases of low-grade MEC. In contrast to low-grade MEC, neither metaplastic WTs nor metaplastic PAs harbored translocations t(11;19) and anticipated t(11;15) resulting in CRTC1-MAML2 and CRTC3-MAML2 fusion transcripts, respectively, and/or MAML2 gene rearrangement.

Salivary duct carcinoma: new developments--morphological variants including pure in situ high grade lesions; proposed molecular classification.

Salivary duct carcinoma (SDC) is an aggressive primary salivary malignancy which microscopically resembles high-grade ductal carcinoma of the breast, with both in situ and invasive patterns. It is typically found in older men, most often in the parotid. It can arise de novo or as the malignant component of carcinoma ex pleomorphic adenoma. SDC is generally a hematoxylin and eosin stain-based diagnosis, with special stains and immunohistochemistry acting mainly in a confirmatory role. Other than epithelial markers, SDC expresses androgen receptors in most cases, with true HER2 positivity seen in about 15 %. Based on these data and analogous to similar schemes in the breast, it is suggested that SDCs can be classified into three main groups: luminal androgen receptor positive, HER2+ and basal phenotype. This may form the basis for prognostic information and new therapeutic possibilities. In addition to the usual type of SDC, a few less common morphological variants have been reported: papillary, micropapillary, mucin-rich, sarcomatoid and oncocytic, as well as pure in situ cases.

Pleomorphic adenoma of the salivary glands with intravascular tumor deposits: a diagnostic pitfall.

The diagnosis of pleomorphic adenoma (PA) of salivary glands is usually straightforward posing few diagnostic problems for the general surgical histopathologist. The purpose of our investigation was to present a series of 22 cases of PA of major salivary glands, each of which contained small foci of tumor within vascular spaces. This feature has previously been described very rarely in PA and may represent a significant diagnostic pitfall. The patients included 12 women and 10 men, ranging in age at diagnosis from 17 to 82 years. Histopathologically, all 22 tumors displayed the features of PA with mixed epithelial and myoepithelial growth patterns and chondromyxoid areas. None of these neoplasms showed any cytologic evidence of malignancy. In all cases, there were multiple dilated thin-walled and/or muscular thick-walled blood vessels containing small intraluminal collections of neoplastic cells with or without myxoid stromal components. The intravascular tumor cells expressed cytokeratins, and in some cases they were also immunoreactive for S-100 protein, GFAP, D2-40, and p63 protein. The intravascular location of the neoplastic cells was confirmed by CD31, CD34, and factor VIII-related antigen immunostains. Reaction for D2-40 was negative in the endothelium of the involved vessel in all cases, confirming that they were vascular rather than lymphatic channels. Seven patients (36%) underwent fine-needle aspiration biopsy 25 days to several years before excision of the tumor. Follow-up of the patients in our series revealed no cases of recurrence or metastasis (range, 6 mo to 9.5 y; mean 3.8 y; median 3.5 y). The biological significance of intravascular tumor in PA is not clear, but there is growing evidence that it is an innocuous phenomenon that might be related to artifactual spillage caused by tumor injury presumably by either fine-needle aspiration or intraoperative trauma.