POU5F1 , encoding a key regulator of stem cell pluripotency, is fused to EWSR1 in hidradenoma of the skin and mucoepidermoid carcinoma of the salivary glands

[Fusion genes in salivary gland tumors]

Salivary gland tumors represent a diagnostic challenge for pathologists due to their rarity, their very wide histopathological and immuno-phenotypic spectrum, and the recent identification of new entities. This article presents the main molecular characteristics of these tumors in order to allow any pathologist to perceive the diagnostic tracks of these ENT tumors and to better guide the molecular approach to establish the diagnosis and guide therapy.

Molecular pathology in diagnosis and prognostication of head and neck tumors

Classification of head and neck tumors has evolved in recent decades including a widespread application of molecular testing in tumors of the salivary glands, sinonasal tract, oropharynx, nasopharynx, and soft tissue. Availability of new molecular techniques allowed for the definition of multiple novel tumor types unique to head and neck sites. Moreover, the expanding spectrum of immunohistochemical markers facilitates a rapid identification of diagnostic molecular abnormalities. As such, it is currently possible for head and neck pathologists to benefit from a molecularly defined classifications, while making diagnoses that are still based largely on histopathology and immunohistochemistry. This review highlights some principal molecular alterations in head and neck neoplasms presently available to assist pathologists in the practice of diagnosis, prognostication and prediction of response to treatment.

Detection of salivary gland and sinonasal fusions by a next-generation sequencing based, ligation-dependent, multiplex RT-PCR assay

AIMS

The discovery of tumour type-specific gene fusion oncogenes in benign and malignant salivary gland and sinonasal (SGSN) tumours has significantly increased our knowledge about their molecular pathology and classification.

METHODS AND RESULTS

We developed a new targeted multiplexed next-generation sequencing (NGS)-based method that utilizes ligation dependent reverse-transcriptase polymerase chain reaction (LD-RT-PCR) to detect oncogenic fusion transcripts involving 116 genes, leading to 96 gene fusions known to be recurrently rearranged in these tumours. In all, 180 SGSN tumours (formalin-fixed, paraffin-embedded samples, 141 specimens and 39 core needle biopsies) from the REFCORpath (French network for rare head and neck cancers) with previously identified fusion genes by fluorescent in situ hybridisation (FISH), RT-PCR, or molecular immunohistochemistry were selected to test its specificity and sensitivity and validate its diagnostic use. Tested tumours encompassed 14 major tumours types, including secretory carcinoma, mucoepidermoid carcinoma, adenoid cystic carcinoma, salivary gland intraductal carcinoma, clear cell carcinoma, pleomorphic adenoma, adamantinoma-like Ewing Sarcoma, EWSR1::COLCA2 sinonasal sarcoma, DEK::AFF2 sinonasal carcinoma, and biphenotypic sinonasal sarcoma. In-frame fusion transcripts were detected in 97.8% of cases (176/180). Gene fusion assay results correlated with conventional techniques (immunohistochemistry [IHC], FISH, and RT-PCR) in 176/180 tumours (97.8%).

CONCLUSION

This targeted multiplexed NGS-based LD-RT-PCR method is a robust, highly sensitive method for the detection of recurrent gene fusions from routine clinical SGSN tumours. It can be easily customized to cover new fusions. These results are promising for implementing an integrated NGS system to rapidly detect genetic aberrations, facilitating accurate, genomics-based diagnoses, and accelerate time to precision therapies in SGSN tumours.

Molecular testing of cytology specimens: overview of assay selection with focus on lung, salivary gland, and thyroid testing

Ancillary and molecular testing of cytopathology specimens has emerged as a reliable and useful tool to provide diagnostic information and treatment-related biomarker status for the management of cancer patients. The cytology specimens obtained through minimally invasive means have proven suitable testing substrates for a variety of ancillary tests, including immunohistochemistry, fluorescence in situ hybridization, as well as polymerase chain reaction and next generation sequencing molecular techniques. By focusing specifically on the cytology specimen, this review provides an overview of basic testing considerations and assay selection in addition to updates on the ancillary testing of cytologic tumor specimens from the lung, salivary gland, and thyroid.

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.

Metastatic mucoepidermoid carcinoma to the pleura: a case report

BACKGROUND

Mucoepidermoid carcinoma is the most common malignant neoplasm arising from the salivary glands (Ali et al. in J Ayub Med Coll Abbottabad 20(2): 141-2, 2008, Xi et al. in World J Surg Oncol 10: 232, 2012). When arising from anatomic sites other than the salivary glands it can be a diagnostic challenge. Primary and metastatic mucoepidermoid carcinoma from and to the pleura are extremely rare entities that are frequently misdiagnosed as adenocarcinoma, adenosquamous carcinoma, or squamous cell carcinoma (Xi et al. in World J Surg Oncol 10: 232, 2012).

CASE PRESENTATION

We describe an unusual case of a 64-year-old Caucasian female patient with metastatic high-grade mucoepidermoid carcinoma to the pleura, morphologically resembling squamous cell carcinoma. Molecular studies of both the parotid gland and pleural tumors helped prove the metastatic nature of the pleural lesion.

CONCLUSIONS

 Metastatic mucoepidermoid carcinoma to the pleura is a rare entity, frequently misdiagnosed as squamous cell carcinoma. Differentiating between a lung primary and a metastatic disease has treatment implications and prognostic significance for the patient. When morphologic and immunophenotypic overlap exists, molecular testing can help distinguish mucoepidermoid carcinoma from other neoplasms.

Recent Advances on Immunohistochemistry and Molecular Biology for the Diagnosis of Adnexal Sweat Gland Tumors

Simple Summary

Cutaneous sweat gland tumors form an extremely diverse and heterogeneous group of neoplasms that show histological differentiation to the sweat apparatus. Due to their rarity, wide diagnostic range, and significant morphological overlap between entities, their accurate diagnosis remains challenging for pathologists. Until recently, little was known about the molecular pathogenesis of adnexal tumors. Recent findings have revealed a wide range of gene fusions and other oncogenic factors that can be used for diagnostic purposes and, for some, can be detected by immunohistochemistry. Among other organs containing exocrine glands, such as salivary glands, breasts, and bronchi, most of these biomarkers have been reported in homologous neoplasms that share morphological features with their cutaneous counterparts. This review aims to describe these recent molecular and immunohistochemical biomarkers in the field of sweat gland tumors.

Abstract

Cutaneous sweat gland tumors are a subset of adnexal neoplasms that derive or differentiate into the sweat apparatus. Their great diversity, rarity, and complex terminology make their pathological diagnosis challenging. Recent findings have revealed a wide spectrum of oncogenic drivers, several of which are of diagnostic interest for pathologists. Most of these molecular alterations are represented by gene fusions, which are shared with other homologous neoplasms occurring in organs containing exocrine glands, such as salivary and breast glands, which show similarities to the sweat apparatus. This review aims to provide a synthesis of the most recent immunohistochemical and molecular markers used for the diagnosis of sweat gland tumors and to highlight their relationship with similar tumors in other organs. It will cover adenoid cystic carcinoma (NFIB, MYB, and MYBL1 fusion), cutaneous mixed tumor (PLAG1 fusion), cylindroma and spiradenoma and their carcinomas thereof (NF-κB activation through CYLD inactivation or ALKP1 hotspot mutation), hidradenoma and hidradenocarcinoma (MAML2 fusion), myoepithelioma (EWSR1 and FUS fusion), poroma and porocarcinoma (YAP1, MAML2, and NUTM1 fusion), secretory carcinoma (ETV6, NTRK3 fusion), tubular adenoma and syringo-cystadenoma papilliferum (HRAS and BRAF activating mutations). Sweat gland tumors for which there are no known molecular abnormalities will also be briefly discussed, as well as potential future developments.

Molecular pathology of skin adnexal tumours

AIMS

Tumours of the cutaneous adnexa arise from, or differentiate towards, structures in normal skin such as hair follicles, sweat ducts/glands, sebaceous glands or a combination of these elements. This class of neoplasms includes benign tumours and highly aggressive carcinomas. Adnexal tumours often present as solitary sporadic lesions, but can herald the presence of an inherited tumour syndrome such as Muir-Torre syndrome, Cowden syndrome or CYLD cutaneous syndrome. In contrast to squamous cell carcinoma and basal cell carcinoma, molecular changes in adnexal neoplasia have been poorly characterised and there are few published reviews on the current state of knowledge.

METHODS AND RESULTS

We reviewed findings in peer-reviewed literature on molecular investigations of cutaneous adnexal tumours published to June 2021.

CONCLUSIONS

Recent discoveries have revealed diverse oncogenic drivers and tumour suppressor alterations in this class of tumours, implicating pathways including Ras/MAPK, PI3K, YAP/TAZ, beta-catenin and nuclear factor kappa B (NF-κB). These observations have identified novel markers, such as NUT for poroma and porocarcinoma and PLAG1 for mixed tumours. Here, we provide a comprehensive overview and update of the molecular findings associated with adnexal tumours of the skin.

Fusion-Positive Salivary Gland Carcinomas

Salivary gland tumors are a rare, heterogeneous group of neoplasms that pose significant diagnostic challenges for the histopathologist. Histopathological diagnosis relies primarily on morphological assessment, with ancillary special stains and immunohistochemistry. In recent years, new defining genomic alterations have been characterized in these 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. These discoveries also help in refining tumor classification. Furthermore, such genetic alterations may have prognostic as well as potentially therapeutic implications in the era of personalized medicine. This review aims at providing a summary of the most recent updates in this field.

Pluripotency Stemness and Cancer: More Questions than Answers

Embryonic stem cells and induced pluripotent stem cells provided us with fascinating new knowledge in recent years. Mechanistic insight into intricate regulatory circuitry governing pluripotency stemness and disclosing parallels between pluripotency stemness and cancer instigated numerous studies focusing on roles of pluripotency transcription factors, including Oct4, Sox2, Klf4, Nanog, Sall4 and Tfcp2L1, in cancer. Although generally well substantiated as tumour-promoting factors, oncogenic roles of pluripotency transcription factors and their clinical impacts are revealing themselves as increasingly complex. In certain tumours, both Oct4 and Sox2 behave as genuine oncogenes, and reporter genes driven by composite regulatory elements jointly recognized by both the factors can identify stem-like cells in a proportion of tumours. On the other hand, cancer stem cells seem to be biologically very heterogeneous both among different tumour types and among and even within individual tumours. Pluripotency transcription factors are certainly implicated in cancer stemness, but do not seem to encompass its entire spectrum. Certain cancer stem cells maintain their stemness by biological mechanisms completely different from pluripotency stemness, sometimes even by engaging signalling pathways that promote differentiation of pluripotent stem cells. Moreover, while these signalling pathways may well be antithetical to stemness in pluripotent stem cells, they may cooperate with pluripotency factors in cancer stem cells - a paradigmatic example is provided by the MAPK-AP-1 pathway. Unexpectedly, forced expression of pluripotency transcription factors in cancer cells frequently results in loss of their tumour-initiating ability, their phenotypic reversion and partial epigenetic normalization. Besides the very different signalling contexts operating in pluripotent and cancer stem cells, respectively, the pronounced dose dependency of reprogramming pluripotency factors may also contribute to the frequent loss of tumorigenicity observed in induced pluripotent cancer cells. Finally, contradictory cell-autonomous and non-cell-autonomous effects of various signalling molecules operate during pluripotency (cancer) reprogramming. The effects of pluripotency transcription factors in cancer are thus best explained within the concept of cancer stem cell heterogeneity.

Update on Molecular Genetic Alterations of Cutaneous Adnexal Neoplasms

Cutaneous adnexal tumors recapitulate follicular, sweat gland, and/or sebaceous epithelia, and range from benign tumors to aggressive carcinomas. Adnexal tumors can be hallmarks for inherited tumor syndromes. Oncogenic drivers of adnexal neoplasms modulate intracellular pathways including mitogen-activated protein kinase, phosphoinositide-3-kinase, Wnt/β-catenin, Hedgehog, nuclear factor κB, and Hippo intracellular signaling pathways, representing potential therapeutic targets. Malignant progression can be associated with tumor suppressor loss, especially TP53. Molecular alterations drive expression of specific diagnostic markers, such as CDX2 and LEF1 in pilomatricomas/pilomatrical carcinomas, and NUT in poromas/porocarcinomas. In these ways, improved understanding of molecular alterations promises to advance diagnostic, prognostic, and therapeutic possibilities for adnexal tumors.

Genomic Analysis of Salivary Gland Cancer and Treatment of Salivary Gland Cancers

Salivary gland cancer is a heterogenous group of tumors that presents challenges with both diagnosis and therapy. Recent advances in the classification of salivary gland cancers have led to distinct histologic and genomic criteria that successfully differentiate between cancers with similar clinical behavior and appearance. Genomic abnormalities have led to the emergence of targeted therapies being used in their therapy with drastic improvements in outcomes as well as reductions in treatment-related toxicity. Dramatic results seen with molecular targets, such as HER2, TRK, and others, indicate that this approach has the potential to yield even better treatments for the future.

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

Salivary gland neoplasms are an uncommon and widely heterogeneous group of tumors. In recent years, there has been considerable progress in efforts to reveal the molecular landscape of these tumors, although it is still limited and appears to be only the tip of the iceberg. Genomic aberrations, especially specific chromosomal rearrangements including CRTC1-MAML2 and CRTC3-MAML2 in mucoepidermoid carcinoma, MYB-NFIB and MYBL1-NFIB fusions in adenoid cystic carcinoma, PLAG1 and HMGA2 alterations in pleomorphic adenoma and carcinoma ex pleomorphic adenoma, ETV6-NTRK3 and ETV6-RET in secretory carcinoma, EWSR1-ATF1 and EWSR1-CREM in clear cell carcinoma, provide new insights into the molecular pathogenesis of various salivary gland neoplasms and help to better classify them. These genetic aberrations primarily serve as diagnostic tools in salivary gland tumor diagnosis; however, some also have promise as prognostic or predictive biomarkers. This review summarizes the latest developments in molecular pathology of salivary gland tumors with a focus on distinctive molecular characteristics.

DNA methyltransferase expression is associated with cell proliferation in salivary mucoepidermoid carcinoma

OBJECTIVES

The present study investigated the correlation between the expression of DNA methyltransferase (DNMT)1, DNMT3A, and DNMT3B and the proliferation of mucoepidermoid carcinomas (MECs) using the molecular markers Ki-67 and cyclin D1. This study also demonstrates the effects of 5-aza-2-deoxycytidine (5AC) on the MEC tumor cell lines in relation to DNMT1 and DNMT3A expression, and cell-cycle arrest.

MATERIALS AND METHODS

The immunohistochemistry of DNMT1, DNMT3A, DNMT3B, Ki-67, and cyclin D1 was analyzed in 40 samples of MEC and 15 samples of healthy minor salivary glands. The effects of 5AC on DNMT1 and DNMT3B expression in MEC cell lines were analyzed by Western blot, and the effects of 5AC on the cell cycle were analyzed using flow cytometry.

RESULTS

The expression of DNMT1 and DNMT3B was more intense in MECs than in healthy salivary glands. A strong correlation was found between the expression of the DNMTs and the proliferation markers. This correlation was validated In Vitro, where treatment with 5AC reduced the expression of the DNMTs and the percentage of cells at the G2/M phase of the cell cycle.

CONCLUSION

The expression of DNMT1, DNMT3A, DNMT3B is correlated significantly with the expression of Ki-67 and cyclin D1. The treatment with 5AC reduces DNMT expression and decreases the percentage of cells at the G2/M phase of the cell cycle, while increasing the cells at the G0/G1 phase.

Undifferentiated round cell sarcomas with novel SS18-POU5F1 fusions

Despite significant recent advances in characterizing the molecular pathogenesis of undifferentiated round cell neoplasms, rare cases remain unclassified. Here, we report two distinctive undifferentiated round cell tumors occurring in young adults. One tumor presented intrabdominally and the other arose within the abdominal wall. One patient died of disease following local and distance recurrence, despite aggressive chemotherapy and radiotherapy. Morphologically, both tumors were similarly composed of primitive round to epithelioid cells arranged in nests, sheets, and trabecular patterns. The cytoplasm was scant and amphophilic, while the nuclei were round and uniform with brisk mitotic activity. Focal necrosis was present. Immunohistochemically, both tumors were variably positive for S100 and EMA, and one case focally expressed cytokeratin and TLE1. Targeted RNA sequencing revealed in both an identical SS18-POU5F1 fusion gene. Fluorescence in situ hybridization was performed which confirmed SS18 and POU5F1 gene rearrangements. Expression data, relative to over 200 other mesenchymal neoplasms that had undergone targeted RNA sequencing on the same platform, suggested the SS18-POU5F1 tumors cluster with EWSR1/FUS-POU5F1-positive myoepithelial tumors. In view of our limited sample size, additional studies are needed to characterize the breadth of clinical and pathologic findings in these neoplasms. In addition, further investigation is necessary to determine whether this entity represents a clinically aggressive and phenotypically undifferentiated variant of myoepithelial tumors, or perhaps an altogether novel category of undifferentiated round cell sarcoma.

Prognostic value of OCT4A and SPP1C transcript variant co-expression in early-stage lung adenocarcinoma

BACKGROUND

Octamer-binding transcription factor 4A (OCT4A) is essential for cell pluripotency and reprogramming both in humans and mice. To date, however, the function of human OCT4 in somatic and/or tumour tissues is largely unknown.

METHODS

RT-PCR was used to identify full-length splice forms of OCT4 transcripts in normal and cancer cells. A FLAG-tagged OCT4 genomic transgene was used to identify OCT4-positive cancer cells. A potential role for OCT4 in somatic cancer cells was examined by cell ablation of OCT4-positive cells using promoter-driven diphtheria toxin A. OCT4 and secreted phosphoprotein 1 (SPP1) transcripts in early-stage lung adenocarcinoma tumours were analysed and compared with pathohistological features.

RESULTS

The results show that, unlike in murine cells, OCT4A and OCT4B variants are transcribed in both human cancer cells and in adult tissues such as lung, kidney, uterus, breast, and eye. We found that OCT4A and SPP1C are co-expressed in highly aggressive human breast, endometrial, and lung adenocarcinoma cell lines, but not in mesothelial tumour cell lines. Ablation of OCT4-positive cells in lung adenocarcinoma cells significantly decreased cell migration and SPP1C mRNA levels. The OCT4A/SPP1C axis was found in primary, early-stage, lung adenocarcinoma tumours.

CONCLUSIONS

Co-expression of OCT4 and SPP1 may correlate with cancer aggressiveness, and the OCT4A/SPP1C axis may help identify early-stage high-risk patients with lung adenocarcinoma. Contrary to the case in mice, our data strongly suggest a critical role for OCT4A and SPP1C in the development and progression of human epithelial cancers.

Salivary Gland Cancer in the Era of Routine Next-Generation Sequencing

Next-Generation Sequencing (NGS) is being utilized with increasing frequency in the characterization of salivary gland tumours. The potential scenarios which may be encountered by using this technique in routine practice will be outlined in further text by drawing from our own clinical experience. These include oncocytic mucoepidermoid carcinomas with unusual variant morphology (and negative MAML2 fluorescent in-situ hybridization results), a diagnosis of ameloblastoma changed to adenoid cystic carcinoma (due to MYBL1 fusion presence), a salivary duct carcinoma with an ETV6-NTRK3 fusion (otherwise seen in secretory carcinomas) and novel fusion partners such as EWSR1-BEND2 (otherwise seen in pancreatic neuroendocrine carcinomas). As NGS continues to develop and more widespread clinical implementation increases, we must be cognisant of the need for proper interpretation and in some cases verification using a secondary technique, the limitations of this technique, and the ethical dilemmas one faces when encountering a novel fusion.

Ewing's sarcoma in the spinal canal of T12-L3: A case report and review of the literature

Primary Ewing's sarcoma (ES) is rare, especially when it occurs in the spinal canal during middle or old age. The rarity of Ewing's sarcoma breakpoint region 1 fusion-negative ES has been reported in the literature. The present case report describes a 60-year-old Chinese patient who was diagnosed with ES originating from the spinal canal in 2016. The patient was hospitalized with pain resembling electric shock in the waist and buttocks, which occurred intermittently for 1 month, and incontinence for 1 week. Magnetic resonance imaging demonstrated multiple inhomogeneous, oval-shaped nodules in the intradural and cauda equina spaces of T12-L3. The largest nodule was ~23×11×10 mm. The patient underwent right adrenal tumour resection. A histopathologic examination of the focal area revealed that the tumour consisted of small, circular haematoxylin stained cells that formed typical Homer-Wright rosettes. Immunohistochemical analysis confirmed that the patient suffered from ES due to positive staining for membranous cluster of differentiation 99 (CD99), cytokeratin (CK) and nuclear foetal-liver infusion 1 (FLI-1). In conclusion, the histopathological presence of Homer-Wright rosettes and immunohistochemical markers such as CD99, FLI-1 and CK are valuable factors for the diagnosis of ES, although cytogenetic analysis is considered the gold standard. Complete surgery is the most effective treatment option for ES treatment. Adjuvant radiotherapy and combination chemotherapy can also improve the survival rate of patients postoperatively.

Prostatic carcinoma with neuroendocrine differentiation harboring the EWSR1-FEV fusion transcript in a man with the WRN G327X germline mutation: A new variant of prostatic carcinoma or a member of the Ewing sarcoma family of tumors?

Since the discovery of the TMPRSS2-ERG fusion transcript in prostatic carcinoma (PCa) more than ten years ago, a long list of recurrent genomic rearrangements involving other transcription factors of the ETS family has been described. Fusions of ETS with the EWSR1 partner gene define many members of the Ewing family of tumors, including primitive neuroectodermal tumor (PNET). Although the expression of EWSR1 appears to be necessary for the oncogenic effects of ETS factors, the EWSR1-ETS rearrangement has never been reported in PCa. Herein, we discuss the pathologic diagnosis of a prostatic tumor in a 44 year-old man, recently treated with finasteride, with the EWSR1-FEV fusion (exon 7: exon 2, join in-frame) discovered by RNA-sequencing and fluorescence in situ hybridization. The tumor was morphologically and immunophenotypically equivocal for a Ewing sarcoma/PNET, and most consistent with a PCa with neuroendocrine differentiation. The patient's family history of PCa led to germline mutation testing by next-generation sequencing showing heterozygosity for the WRN^G327X mutation. The WRN protein along with ATM, BRCA1, BRCA2, and RAD51 among others, comprise a DNA repair system by homologous recombination, and its alterations are associated with forms of hereditary PCa. We dispute whether the detection of EWSR1-FEV mandates one to diagnose the patient's tumor as a member of the Ewing sarcoma family.

High Grade Transformation in Mucoepidermoid Carcinoma of the Minor Salivary Gland with Polyploidy of the Rearranged MAML2 Gene

Mucoepidermoid carcinoma (MEC) is the most common malignant tumor of the salivary gland. However, reports of high grade transformation in MEC are extremely rare, and only two cases have so far been described. Recent development of salivary gland pathology revealed recurrent gene rearrangements in many kinds of tumors, including MAML2 fusion of MEC. To date, the MAML2 status of high grade transformed MEC has not been studied. Here we report the first case of minor salivary gland origin high grade transformation in MEC with a MAML2 break apart FISH study. A 73-year-old woman presented with a 1-month history of left mandibular area swelling, and computed tomography and magnetic resonance imaging revealed a mass in the hard palate with various-sized lymphadenopathy of the neck. The resected tumor histologically consisted of two carcinomatous components. Approximately 30% of the tumor showed a conventional MEC feature, while 70% was comprised of a high grade transformed component. In the conventional MEC component, FISH revealed MAML2 rearrangement. High grade transformed cells showed multiple split signals, and the results were interpreted as rearrangement and polyploidy after comparison with 1p/19q FISH as validation. The patient received adjuvant radiation therapy after wide resection with neck dissection and retropharyngeal dissection. Nevertheless, as the remaining tumor grew up rapidly and metastatic lymph nodes were newly revealed, the patient expired 7 months after the diagnosis. We first report regarding a high grade transformation in MEC with polyploidy of the rearranged MAML2 gene and aggressive biological behavior.

EWSR1, a multifunctional protein, regulates cellular function and aging via genetic and epigenetic pathways

Ewing's sarcoma (EWS) is a bone cancer arising predominantly in young children. EWSR1 (Ewing Sarcoma breakpoint region 1/EWS RNA binding protein 1) gene is ubiquitously expressed in most cell types, indicating it has diverse roles in various cellular processes and organ development. Recently, several studies have shown that missense mutations of EWSR1 genes are known to be associated with central nervous system disorders such as amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Otherwise, EWSR1 plays epigenetic roles in gene expression, RNA processing, and cellular signal transduction. Interestingly, EWSR1 controls micro RNA (miRNA) levels via Drosha, leading to autophagy dysfunction and impaired dermal development. Ewsr1 deficiency also leads to premature senescence of blood cells and gamete cells with a high rate of apoptosis due to the abnormal meiosis. Despite these roles of EWSR1 in various cellular functions, the exact mechanisms are not yet understood. In this context, the current review overviews a large body of evidence and discusses on what EWSR1 genetic mutations are associated with brain diseases and on how EWSR1 modulates cellular function via the epigenetic pathway. This will provide a better understanding of bona fide roles of EWSR1 in aging and its association with brain disorders.

Mesenchymal Tumors with EWSR1 Gene Rearrangements

Among the various genes that can be rearranged in soft tissue neoplasms associated with nonrandom chromosomal translocations, EWSR1 is the most frequent one to partner with other genes to generate recurrent fusion genes. This leads to a spectrum of clinically and pathologically diverse mesenchymal and nonmesenchymal neoplasms, variably manifesting as small round cell, spindle cell, clear cell or adipocytic tumors, or tumors with distinctive myxoid stroma. This review summarizes the growing list of mesenchymal neoplasms that are associated with EWSR1 gene rearrangements.

Expanding primary cells from mucoepidermoid and other salivary gland neoplasms for genetic and chemosensitivity testing

Restricted availability of cell and animal models is a rate-limiting step for investigation of salivary gland neoplasm pathophysiology and therapeutic response. Conditionally reprogrammed cell (CRC) technology enables establishment of primary epithelial cell cultures from patient material. This study tested a translational workflow for acquisition, expansion and testing of CRC-derived primary cultures of salivary gland neoplasms from patients presenting to an academic surgical practice. Results showed that cultured cells were sufficient for epithelial cell-specific transcriptome characterization to detect candidate therapeutic pathways and fusion genes, and for screening for cancer risk-associated single nucleotide polymorphisms (SNPs) and driver gene mutations through exome sequencing. Focused study of primary cultures of a low-grade mucoepidermoid carcinoma demonstrated amphiregulin-mechanistic target of rapamycin-protein kinase B (AKT; AKT1) pathway activation, identified through bioinformatics and subsequently confirmed as present in primary tissue and preserved through different secondary 2D and 3D culture media and xenografts. Candidate therapeutic testing showed that the allosteric AKT inhibitor MK2206 reproducibly inhibited cell survival across different culture formats. By contrast, the cells appeared resistant to the adenosine triphosphate competitive AKT inhibitor GSK690693. Procedures employed here illustrate an approach for reproducibly obtaining material for pathophysiological studies of salivary gland neoplasms, and other less common epithelial cancer types, that can be executed without compromising pathological examination of patient specimens. The approach permits combined genetic and cell-based physiological and therapeutic investigations in addition to more traditional pathologic studies, and can be used to build sustainable bio-banks for future inquiries.This article has an associated First Person interview with the first author of the paper.

Applications of molecular testing in surgical pathology of the head and neck

Molecular testing in routine surgical pathology is becoming an important component of the workup of many different types of tumors. In fact, in some organ systems, guidelines now suggest that the standard of care is to obtain specific molecular panels for tumor classification and/or therapeutic planning. In the head and neck, clinically applicable molecular tests are not as abundant as in other organ systems. Most current head and neck biomarkers are utilized for diagnosis rather than as companion diagnostic tests to predict therapeutic response. As the number of potential molecular biomarker assays increases and cost pressures escalate, the pathologist must be able to navigate the molecular testing pathways. This review explores scenarios in which molecular testing might be beneficial and cost-effective in head and neck pathology.

Papillary adnexal neoplasm (aggressive digital papillary adenocarcinoma) on the ankle of a 15-year-old girl: case report and review of literature from a pediatric perspective

Digital papillary adenocarcinoma is a rare malignant tumor of the sweat glands, most commonly encountered in adult males. Only few pediatric cases have been reported, with an apparent predominance of females and none on the ankle. We report a case of a 15-year-old girl with a slowly growing, non-tender mass on the right ankle presenting with difficulty in walking; clinically believed to be a keloid. Excision of the mass revealed a glandular neoplasm with largely eccrine and focally apocrine differentiation. Histologic features do not reliably predict biologic behavior. Because of the existing confusion over the nomenclature, we propose that such tumors be called 'papillary adnexal neoplasms of distal extremities'.

Molecular Pathology and Biomarkers

The field of salivary gland tumor biology is quite broad, given the numerous subtypes of both benign and malignant tumors originating from the major and minor salivary glands. Knowledge about the molecular pathology of these lesions is still limited, and there are few clinically useful diagnostic and prognostic biomarkers. However, recent discoveries of certain key genomic alterations, such as chromosome translocations, copy number alterations, and mutations, provide new insights into the molecular pathogenesis of these lesions and may help to better define them. It is also hoped that this new knowledge can help to guide therapy, but this translation has been somewhat slow to develop, perhaps due to the rarity of these tumors and the lack of large, randomized studies. However, because of the limitations inherent in what surgery and radiation can provide, there is an urgent need for understanding of the mechanisms of carcinogenesis in these tumors individually, so that chemotherapy and/or targeted therapy can be rationally selected.

The landscape of gene fusions and somatic mutations in salivary gland neoplasms - Implications for diagnosis and therapy

Recent studies of the genomic landscape of salivary gland tumors have provided important insights into the molecular pathogenesis of these tumors. The most consistent alterations identified include a translocation-generated gene fusion network involving transcription factors, transcriptional coactivators, tyrosine kinase receptors, and other kinases. In addition, next-generation sequencing studies of a few subtypes of salivary neoplasms have revealed hotspot mutations in individual genes and mutations clustering to specific pathways frequently altered in cancer. Although limited, these studies have opened up new avenues for improved classification and targeted therapies of salivary gland cancers. In this review, we summarize the latest developments in this field, focusing on tumor types for which clinically important molecular data are available.

Landscape of gene fusions in epithelial cancers: seq and ye shall find

Enabled by high-throughput sequencing approaches, epithelial cancers across a range of tissue types are seen to harbor gene fusions as integral to their landscape of somatic aberrations. Although many gene fusions are found at high frequency in several rare solid cancers, apart from fusions involving the ETS family of transcription factors which have been seen in approximately 50% of prostate cancers, several other common solid cancers have been shown to harbor recurrent gene fusions at low frequencies. On the other hand, many gene fusions involving oncogenes, such as those encoding ALK, RAF or FGFR kinase families, have been detected across multiple different epithelial carcinomas. Tumor-specific gene fusions can serve as diagnostic biomarkers or help define molecular subtypes of tumors; for example, gene fusions involving oncogenes such as ERG, ETV1, TFE3, NUT, POU5F1, NFIB, PLAG1, and PAX8 are diagnostically useful. Tumors with fusions involving therapeutically targetable genes such as ALK, RET, BRAF, RAF1, FGFR1-4, and NOTCH1-3 have immediate implications for precision medicine across tissue types. Thus, ongoing cancer genomic and transcriptomic analyses for clinical sequencing need to delineate the landscape of gene fusions. Prioritization of potential oncogenic "drivers" from "passenger" fusions, and functional characterization of potentially actionable gene fusions across diverse tissue types, will help translate these findings into clinical applications. Here, we review recent advances in gene fusion discovery and the prospects for medicine.

Fusion of the genes EWSR1 and PBX3 in retroperitoneal leiomyoma with t(9;22)(q33;q12)

Retroperitoneal leiomyoma is a rare benign smooth muscle tumor almost exclusively found in women and with histopathological features similar to uterine leiomyomas. The pathogenesis of retroperitoneal leiomyoma is unclear and next to nothing is known about the cytogenetics and molecular genetics of the tumor. We present here a retroperitoneal leiomyoma with a t(9;22)(q33;q12) as the sole karyotypic aberration. The translocation resulted in an EWSR1-PBX3 fusion gene in which exon 9 of EWSR1 (nucleotide 1320 accession number NM_013986 version 3) was in-frame fused to exon 5 of PBX3 (nucleotide 824 accession number NM_006195 version 5). The EWSR1-PBX3 fusion transcript codes for a 529 amino acids long chimeric EWSR1-PBX3 protein which contains the N-terminal transactivation part of EWSR1 and the homeodomain of PBX3. The present study, together with our previous finding of a retroperitoneal leiomyoma with t(10;17)(q22;q21) as the sole karyotypic aberration and a KAT6B-KANSL1 fusion gene, indicates that retroperitoneal leiomyomas may be characterized by fusion genes coding for chimeric proteins. However, cytogenetic and molecular heterogeneity exists in these tumors and it is too early to tell how many and which different pathways lead to retroperitoneal leiomyomagenesis.

Malignant round cell tumor of bone with EWSR1-NFATC2 gene fusion

Gene rearrangements involving the Ewing sarcoma breakpoint region 1 (EWSR1) gene are seen in a broad range of sarcomas and some nonmesenchymal neoplasms. Ewing sarcoma is molecularly defined by a fusion of the EWSR1 gene (or rarely the related FUS gene) to a member of the E26 transformation-specific (ETS) family of transcription factors, frequently the EWSR1-FLI1 fusion. More recently, EWSR1 gene fusion to non-ETS family members, including the nuclear factor of activated T cells, cytoplasmic, calcineurin-dependent 2 (NFATC2) gene, has been reported in a histological variant of Ewing sarcoma. Here, we report a malignant round cell tumor of bone with an EWSR1-NFATC2 fusion gene. This report builds upon the unusual morphological and clinical presentation of bone neoplasms containing an EWSR1-NFATC2 fusion gene.

Mammary analogue secretory carcinoma: update on a new diagnosis of salivary gland malignancy

OBJECTIVES/HYPOTHESIS

To review the known histopathologic findings and clinical behavior of mammary analogue secretory carcinoma (MASC).

DATA SOURCES

PubMed.

REVIEW METHODS

Literature search using the terms "Mammary analogue secretory carcinoma," "Mammary analog secretory carcinoma," and "MASC" to identify all relevant publications.

RESULTS

MASC is an unusual and rare malignant salivary gland tumor first described in 2010. It shares histologic, immunohistochemical, and genetic features with secretory carcinoma of the breast. The clinical behavior of MASC ranges from slowly growing tumors that infrequently recur after surgical resection to aggressive tumors that cause widespread metastasis and death. Many cases of MASC were discovered in archived cases previously classified as acinic cell carcinoma, mucoepidermoid carcinoma, and adenocarcinoma not otherwise specified.

CONCLUSION

MASC is a newly recognized variant of salivary gland malignancy. Further research is needed to better delineate its overall prevalence and to define an appropriate treatment algorithm for this new clinical entity.

Fusion oncogenes in salivary gland tumors: molecular and clinical consequences

Salivary gland tumors constitute a heterogeneous group of uncommon diseases that pose significant diagnostic and therapeutic challenges. However, the recent discovery of a translocation-generated gene fusion network in salivary gland carcinomas as well in benign salivary gland tumors opens up new avenues for improved diagnosis, prognostication, and development of specific targeted therapies. The gene fusions encode novel fusion oncoproteins or ectopically expressed normal or truncated oncoproteins. The major targets of the translocations are transcriptional coactivators, tyrosine kinase receptors, and transcription factors involved in growth factor signaling and cell cycle regulation. Notably, several of these targets or pathways activated by these targets are druggable. Examples of clinically significant gene fusions in salivary gland cancers are the MYB-NFIB fusion specific for adenoid cystic carcinoma, the CRTC1-MAML2 fusion typical of low/intermediate-grade mucoepidermoid carcinoma, and the recently identified ETV6-NTRK3 fusion in mammary analogue secretory carcinoma. Similarly, gene fusions involving the PLAG1 and HMGA2 oncogenes are specific for benign pleomorphic adenomas. Continued studies of the molecular consequences of these fusion oncoproteins and their down-stream targets will ultimately lead to the identification of novel driver genes in salivary gland neoplasms and will also form the basis for the development of new therapeutic strategies for salivary gland cancers and, perhaps, other neoplasms.

Mammary analogue secretory carcinoma of salivary gland origin: an update and expanded morphologic and immunohistochemical spectrum of recently described entity

Mammary analogue secretory carcinoma of salivary gland origin (MASC) is a recently described tumor with ETV6 translocation. Akin to secretory breast cancer, MASC expresses S-100 protein, mammaglobin, vimentin, and harbors a t(12;15) (p13;q25) translocation which leads to ETV6-NTRK3 fusion product. Histologically, MASC displays a lobulated growth pattern and is often composed of microcystic, tubular, and solid structures with abundant eosinophilic homogeneous or bubbly secretions. Colloid-like secretory material stains positive for periodic acid-Schiff (PAS) with and without diastase and for Alcian blue. The cells of MASC are devoid of PAS-positive secretory zymogen granules. These features help to exclude the most important differential diagnostic considerations, namely acinic cell carcinoma, low-grade cribriform cystadenocarcinoma, cystadenocarcinoma (not otherwise specified), and low-grade mucoepidermoid carcinoma. To date the presence of the ETV6-NTRK3 fusion gene has not been demonstrated in any other salivary gland tumor than MASC. It is likely that MASC is more common than currently recognized and with further studies, the clinical need for molecular studies of the ETV6-NTRK3 fusion may diminish. However, molecular testing is recommended at this time to arrive at the diagnosis of MASC.

Carcinoma of the thyroid with ewing family tumor elements and favorable prognosis: report of a second case

The rare reports of primary, nonneuroendocrine small cell carcinomas of the thyroid have not provided enough evidence to support the recognition of these tumors as an entity or to understand their etiopathogenesis. We report the second case of a primary, nonneuroendocrine small cell carcinoma of the thyroid displaying diffuse expression of cytokeratins, CD99, and p63, in the absence of vimentin expression, in a 24-year-old male who is alive without any signs of disease 13 years after total thyroidectomy and radioactive iodine. The tumor disclosed the EWSR1-FLI1 rearrangement, and we propose to designate it as a carcinoma of the thyroid with Ewing family tumor elements.

Unusual myoid, perivascular, and postradiation lesions, with emphasis on atypical vascular lesion, postradiation cutaneous angiosarcoma, myoepithelial tumors, myopericytoma, and perivascular epithelioid cell tumor

In recent years, a number of new soft tissue tumor entities have been described that occur in the skin only, or that also occur in other sites but form clinically and pathologically distinct subsets when arising in the skin and subcutaneous tissue. These include a variety of mesenchymal lineages and have variable malignant potential, although superficial malignant soft tissue tumors generally have a more favorable outcome than their more deeply located counterparts. This article reviews the clinical and pathologic features and differential diagnoses of atypical vascular lesion, postradiation cutaneous angiosarcoma, myoepithelioma, myopericytoma, and perivascular epithelioid cell tumor.

What the EWSR1-ATF1 fusion has taught us about hyalinizing clear cell carcinoma

Hyalinizing clear cell carcinoma (HCCC) is a unique low-grade tumor composed of cords and nests of clear cells in a hyalinized stroma that was first reported by Milchgrub et al. It was recognized as a separate entity from clear cell variants of epithelial-myoepithelial carcinoma, myoepithelial carcinoma and mucoepidermoid carcinoma. HCCC is included in a long list of clear cell-containing tumors of salivary gland, as well as odontogenic tumors and metastases (renal cell carcinoma). Up until now, it has been considered a diagnosis of exclusion, despite its very distinctive appearance, and labeled as "not otherwise specified" by the World Health Organization. The emergence of molecular data in salivary gland tumors, including HCCC now allow for a more rigorous appraisal of its spectrum. The EWSR1-ATF1 fusion has proven the concept of a "mucinous HCCC" and removes mucin as an exclusion criterion for this tumor. It has also proven a genetic link between clear cell odontogenic carcinoma and HCCC. Molecularly-proven cases have also highlighted variant morphologies and shown that cases with overt squamous differentiation are true HCCC. This gives further weight to the classification of this tumor as squamous or adenosquamous in differentiation and as a specific entity rather than an "NOS" tumor.

Genomic profiles and CRTC1-MAML2 fusion distinguish different subtypes of mucoepidermoid carcinoma

Mucoepidermoid carcinoma is the most common salivary gland malignancy, and includes a spectrum of lesions ranging from non-aggressive low-grade tumors to aggressive high-grade tumors. To further characterize this heterogeneous group of tumors we have performed a comprehensive analysis of copy number alterations and CRTC1-MAML2 fusion status in a series of 28 mucoepidermoid carcinomas. The CRTC1-MAML2 fusion was detected by RT-PCR or fluorescence in situ hybridization in 18 of 28 mucoepidermoid carcinomas (64%). All 15 low-grade tumors were fusion-positive whereas only 3 of 13 high-grade tumors were fusion-positive. High-resolution array-based comparative genomic hybridization revealed that fusion-positive tumors had significantly fewer copy number alterations/tumor compared with fusion-negative tumors (1.5 vs 9.5; P=0.002). Twelve of 18 fusion-positive tumors had normal genomic profiles whereas only 1 out of 10 fusion-negative tumors lacked copy number alterations. The profiles of fusion-positive and fusion-negative tumors were very similar to those of low- and high-grade tumors. Thus, low-grade mucoepidermoid carcinomas had significantly fewer copy number alterations/tumor compared with high-grade mucoepidermoid carcinomas (0.7 vs 8.6; P<0.0001). The most frequent copy number alterations detected were losses of 18q12.2-qter (including the tumor suppressor genes DCC, SMAD4, and GALR1), 9p21.3 (including the tumor suppressor genes CDKN2A/B), 6q22.1-q23.1, and 8pter-p12.1, and gains of 8q24.3 (including the oncogene MAFA), 11q12.3-q13.2, 3q26.1-q28, 19p13.2-p13.11, and 8q11.1-q12.2 (including the oncogenes LYN, MOS, and PLAG1). On the basis of these results we propose that mucoepidermoid carcinoma may be subdivided in (i) low-grade, fusion-positive mucoepidermoid carcinomas with no or few genomic imbalances and favorable prognosis, (ii) high-grade, fusion-positive mucoepidermoid carcinomas with multiple genomic imbalances and unfavorable prognosis, and (iii) a heterogeneous group of high-grade, fusion-negative adenocarcinomas with multiple genomic imbalances and unfavorable outcome. Taken together, our studies indicate that molecular genetic analysis can be a useful adjunct to histologic scoring of mucoepidermoid carcinoma and may lead to development of new clinical guidelines for management of these patients.

Tumors with EWSR1-CREB1 and EWSR1-ATF1 fusions: the current status

EWSR1-CREB1 and EWSR1-ATF1 are gene fusions of which one or both have now been consistently described in 5 histopathologically and behaviorally diverse neoplasms: angiomatoid fibrous histiocytoma, conventional clear cell sarcoma (of tendons and aponeuroses), clear cell sarcoma-like tumor of the gastrointestinal tract, hyalinizing clear cell carcinoma of the salivary gland, and primary pulmonary myxoid sarcoma. Some of the tumors in this group have been described only recently, and others have been the subject of recent genetic insights contributing to their characterization. These neoplasms are all rare; yet, the increasing frequency with which EWSR1-CREB1 and EWSR1-ATF1 fusions are being described in separate entities is noteworthy. The additional molecular mechanisms by which tumors with such variable morphologic, immunohistochemical, and clinical phenotypes are generated are yet to be understood. We review the clinicopathologic and molecular features of this group of neoplasms unified by the presence of EWSR1-CREB1 and EWSR1-ATF1 genetic fusions.