MECT1-MAML2 fusion transcript defines a favorable subset of mucoepidermoid carcinoma

Molecular Alterations in Pediatric Solid Tumors

Pediatric tumors can be divided into hematologic malignancies, central nervous system tumors, and extracranial solid tumors of bone, soft tissue, or other organ systems. Molecular alterations that impact diagnosis, prognosis, treatment, and familial cancer risk have been described in many pediatric solid tumors. In addition to providing a concise summary of clinically relevant molecular alterations in extracranial pediatric solid tumors, this review discusses conventional and next-generation sequencing-based molecular techniques, relevant tumor predisposition syndromes, and the increasing integration of molecular data into the practice of diagnostic pathology for children with solid tumors.

Critical Appraisal of Histologic Grading for Mucoepidermoid Carcinoma of Salivary Gland: Is an Objective Prognostic 2-tiered Grading System Possible?

Multiple 3-tiered grading systems exist for mucoepidermoid carcinoma (MEC), leading to controversial results on the frequency and prognostic values of each grade. We aimed to identify prognostic histologic factors and to evaluate grading schemes in this retrospective study of 262 resected primary head and neck MECs. The rate of nodal metastasis was 8.4%. Large tumor size, tumor fibrosis, infiltrative border, lymphovascular invasion, perineural invasion, atypical mitosis, mitotic index (MI) ≥4/2 mm 2 (4/10 HPFs), necrosis, and pT4 stage were associated with increased risk of nodal metastasis. The 5-year recurrence-free survival (RFS) was 95%. Significant prognostic factors for RFS included infiltrative border, tumor-associated lymphoid stroma, architectural patterns (macrocystic, microcystic, and noncystic), anaplasia, atypical mitosis, MI, necrosis, lymphovascular invasion, margin, pT stage, and tumor size. Nuclear anaplasia, high mitotic rate, and ≥25% microcystic component were significant independent prognostic factors on multivariate survival analysis. There was no significant difference between low-grade (LG) and intermediate-grade (IG) MECs in terms of risk of nodal metastasis and outcomes using all 4 known grading systems. Rather, high-grade MEC was consistently associated with an increased risk of nodal metastasis at presentation and decreased RFS and distant metastasis-free survival (DMFS) compared with the LG/IG MECs. We therefore recommend simplifying MEC grading to a 2-tiered grading scheme using MI and/or tumor necrosis. Using a 2-tiered grading, high-grade histology independently predict RFS, and is associated with a 25% risk of nodal metastasis, a 5-year RFS of 76%, and a 5-year DMFS of 76%, whereas LG MEC has a nodal metastasis rate of 7.0%, 5-year RFS of 97% and 5-year DMFS of 99%.

Salivary Gland Neoplasms With a Unique Trabecular Histology and MAML2 Translocation : A Trabecular Variant of a Mucoepidermoid Carcinoma

Mucoepidermoid carcinomas (MECs) are the most common salivary gland malignancy and have a diverse histology. Many histologic variants of MEC have now been confirmed with characteristic molecular alterations involving CRTC1::MAML2 or CRTC1::MAML3 translocations. We here report a series of 7 trabecular variants of MEC which showed a predominant trabecular or nested pattern with either focal glandular differentiation or clear cell change and keloid-like fibrosis in the background. In addition, these tumors were either negative or showed only focal positivity for p63. Such features are not characteristic of known disease entities and resulted in an initial misdiagnosis of adenocarcinoma, not otherwise specified, or low-grade to intermediate-grade MEC with uncertainty. The patients' ages in our cohort ranged from 26 to 55 years with a female predominance (5/7). The tumors were located in the parotid gland (n=3), base of tongue (n=2), hard palate (n=1), and parapharyngeal space (n=1), with a median size of 1.5 cm. All 7 cases showed an MAML2 split pattern on fluorescence in situ hybridization analysis, and both RNA and whole-genome sequencing presented CRTC1::MAML2 translocation. All 7 cases showed a solid-predominant histology, and 3 cases displayed extracapsular extension. There were no other signs of high-grade histology and no recurrences or deaths occurred over a follow-up period of up to 79 months. We thus propose a unique trabecular variant of MEC that has atypical histologic and immunohistochemical features.

Pulmonary mucoepidermoid carcinoma in children: two case reports and a review of the literature

Pulmonary mucoepidermoid carcinoma (PMEC) is a rare tumor, particularly in children, and its clinical manifestations vary. When the tumor is small, it may be asymptomatic; however, with larger tumors, patients may present with symptoms such as recurring pneumonia, atelectasis, persistent cough, chest pain, and even hemoptysis. PMEC appears as an exophytic intrabronchial mass. This study aims to report on the clinical manifestations, imaging findings, treatment approaches, and prognosis of two children diagnosed with PMEC at our hospital between January 2018 and December 2022. The age of onset for both children was 9 years, and the masses were located in the right upper lobe bronchi. Following surgical treatment, both patients showed a good prognosis. In addition, we conducted a comprehensive review of the relevant literature to enhance the overall understanding of PMEC.

The Challenge of "Monomorphic" Mucoepidermoid Carcinoma-Report of a Rare Case with Pure Spindle-Clear Cell Morphology

BACKGROUND

Mucoepidermoid carcinoma is a malignant salivary gland tumor which, in most cases, is composed of variable proportions of mucous, epidermoid, and intermediate cells.

METHODS

We report a case of parapharyngeal mucoepidermoid carcinoma with highly unusual ("monomorphic") light microscopic features as well as atypical immunohistochemical properties. Molecular analysis was performed using the TruSight RNA fusion panel.

RESULTS

The tumor featured heretofore undescribed histopathological features: sheets and nests composed of monomorphic neoplastic (plump spindle to epithelioid) cells with no mucous, intermediate, glandular/columnar, or any other cell type identified. The neoplastic cells displayed variable clear cell change and only expressed cytokeratin 7. Despite this non-classical morphology, the presence of the classical CRTC1::MAML2 fusion was demonstrated.

CONCLUSIONS

Mucoepidermoid carcinoma featuring a uniform ("monomorphic") population of neoplastic cells is a novel observation. A confident diagnosis of mucoepidermoid carcinoma can be made upon detection of the CRTC1/3::MAML2 fusion. Our case increases the spectrum of histopathological appearances that mucoepidermoid carcinoma may display.

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.

Intrahepatic cholangiocarcinoma: typical features, uncommon variants, and controversial related entities

Pathologists play a central role in the diagnosis and classification of intrahepatic cholangiocarcinoma (iCCA). iCCA is currently classified into small- and large-duct types. Small-duct iCCA is characterized by a mass-forming gross appearance, mucus-poor ductule-like histology, and frequent association with chronic parenchymal liver diseases (eg, cirrhosis). Large-duct iCCA is an infiltrative duct-forming adenocarcinoma with a fibrotic stroma, similar to perihilar cholangiocarcinoma. Chronic cholangiopathies (eg, primary sclerosing cholangitis, liver flukes) are associated with an increased risk of large-duct iCCA. Alterations in IDH1/2, BAP1, or FGFR2 are characteristic molecular features of small-duct iCCA, whereas mutations in KRAS and SMAD4 and the amplification of MDM2 are mainly observed in large-duct iCCA. C-reactive protein and N-cadherin are commonly expressed in small-duct iCCA, and S100P is a good marker for large-duct iCCA. In addition to well-known subtypes (eg, cholangiolocellular carcinoma), uncommon variants are recognized. A tubulocystic variant is often misinterpreted as a benign neoplasm. Mucoepidermoid and enteroblastic variants are under-recognized and pose a diagnostic challenge. Cholangioblastic cholangiocarcinoma characterized by inhibin-A expression was recently found to have an NIPBL-NACC1 gene fusion. Despite significant advances in hepatobiliary pathology, there are still controversial premalignant entities that require large comprehensive studies. There are morphological overlaps between biliary adenofibroma and the tubulocystic variant of iCCA. Type 2 intraductal papillary neoplasm of the bile duct (IPNB) is typically associated with invasive malignancy at the initial presentation and lacks unique molecular features. Therefore, some pathologists prefer the term "papillary cholangiocarcinoma" over type 2 IPNB.

Establishment of Mucoepidermoid Carcinoma Cell Lines from Surgical and Recurrence Biopsy Specimens

Patients with advanced/recurrent mucoepidermoid carcinoma (MEC) have a poor prognosis. This study aimed to establish and characterize human mucoepidermoid carcinoma cell lines from the initial surgical specimen and biopsy specimen upon recurrence from the same patient to provide a resource for MEC research. MEC specimens from the initial surgical procedure and biopsy upon recurrence were used to establish cell lines. The established cell lines were cytogenetically characterized using multi-color fluorescence in situ hybridization and detection, and the sequence of the CRTC1-MAML2 chimeric gene was determined. Furthermore, the susceptibility of head and neck mucoepidermoid carcinoma to standard treatment drugs such as cisplatin, 5-fluorouracil, and cetuximab was investigated. We successfully established unique MEC cell lines, AMU-MEC1, from an initial surgical specimen and AMU-MEC1-R1 and AMU-MEC1-R2 from the recurrent biopsy specimen in the same patient. These cell lines exhibited epithelial morphology and developed in vitro-like cobblestones. They shared eight chromosomal abnormalities, including der(19)ins(19;11)(p13;?), which resulted in a chimeric CRTC1-MAML2 gene, indicating the same origin of the cell lines. The susceptibility of all cell lines to cisplatin and 5-fluorouracil was low. Interestingly, EGFR dependency for cell growth decreased in AMU-MEC-R1 and AMU-MEC-R2 but was retained in AMU-MEC1. These cytogenetic and biochemical findings suggest that the established cell lines can be used to investigate the disease progression mechanisms and develop novel therapeutics for MEC.

Thymic Mucoepidermoid Carcinoma: A Clinicopathologic and Molecular Study

Thymic mucoepidermoid carcinoma (MEC) is a rare tumor, and its characteristics remain to be clarified. Here we investigated 20 cases of thymic MEC to systematically characterize its clinical, histopathologic, and molecular features. The median age of the patients was 56 years (range, 19 to 80 y), there was a slight male predilection (3:2), and 44% of the patients were asymptomatic at diagnosis. The median tumor size was 6.8 cm in diameter, 55% were pT1 tumors, and 50% were TNM stage I tumors. When 4 tumor grading systems for salivary MEC (Armed Forces Institutes of Pathology, Brandwein, modified Healey, and the Memorial Sloan-Kettering) were employed, low-grade, intermediate-grade, and high-grade tumors accounted for 35% to 70%, 5% to 25%, and 25% to 50%, respectively. Many histologic variants were noted, and 70% of the cases were classified as nonclassic variants. MAML2 rearrangement was detected in 56% of cases, and the fusion partner was CRTC1 in all cases. CRTC1-MAML2 fusion was associated with lower pT classification and lower TNM stage. The overall survival rate of all patients was 69% and 43% at 5 and 10 years, respectively. Worse overall survival was associated with higher pT stage, higher TNM stage, residual tumors, greater tumor size, high-grade tumor histology (Armed Forces Institutes of Pathology and Memorial Sloan-Kettering, but not the other 2), and with the absence of CRTC1-MAML2 fusion. Of note, none of the patients with CRTC1-MAML2 fusion-positive tumors died during the follow-up. In conclusion, the clinicopathologic and molecular findings of thymic MEC presented here are expected to contribute to the management of this rare tumor.

A retrospective study of parotid gland tumors at a single institution

The aim of the present study was to analyze the clinical characteristics, surgical treatments and clinical outcome of patients with parotid gland tumors and to compare the results with those cited in the literature. A retrospective study was conducted in 140 patients (male, n=77; female, n=63) with parotid gland tumors who underwent parotidectomy at Hokuto Hospital Department of Otolaryngology-Head and Neck Surgery (Obihiro, Japan) between April 2007 and December 2021. Of the 140 patients enrolled, 118 (84.3%) patients had benign tumors, including 63 (45%) patients with pleomorphic adenomas and 43 (30.7%) patients with Warthin tumors, and 22 patients (15.7%) had parotid carcinoma. Comparison of the three groups of patients with parotid gland tumors indicated that pack years as an indicator of smoking status were significantly higher in patients with Warthin tumors than in those with parotid carcinomas (P=0.011) or pleomorphic adenoma (P<0.001). Fine-needle aspiration cytology (FNAC) was non-diagnostic for only 6 (4.3%) of 140 patients. The sensitivity, specificity, positive predictive value, negative predictive value and accuracy of FNAC by both conventional smear and liquid-based cytology (LBC) for parotid carcinomas were 70, 99, 93.3, 94.4 and 82.9%, respectively. Among the 22 patients with parotid carcinoma, extended total/total and superficial parotidectomy were performed in 10 (45%) and 11 (50%) cases, respectively. Total and selective neck dissection of the area from level II to I, II and III were performed in 6 (24%) and 7 (32%) patients, respectively. Postoperative radiotherapy (50 Gy) was performed in 15 (68%) patients. The overall survival (OS) and disease-free survival (DFS) rates at 5 years were 51.5 and 76.4%, respectively. Univariate analysis revealed that age >65 years was significantly associated with poorer 5-year OS (P<0.001) and DFS (P<0.001). Multivariate analysis revealed that an age of more than 65 years combined with high-grade histologic malignancy was associated with worse DFS (P=0.02; hazard ratio, 3.628; 95% confidence interval, 1.283-9.514). In conclusion, the clinical characteristics and treatment outcomes of parotid gland tumors were consistent with the results of previous reports. Smoking may be closely related to the pathogenesis of Warthin tumors. LBC potentially provides improved accuracy in FNAC.

Primary Mucoepidermoid Carcinoma of the Lacrimal Apparatus

PURPOSE

In this study, we evaluated the clinicopathologic and molecular characteristics of lacrimal apparatus mucoepidermoid carcinoma (MEC) to define its typical diagnostic features.

DESIGN

Retrospective observational case series.

METHODS

Institutional pathology records between 2011 and 2021 were searched for all cases of lacrimal apparatus MEC.

RESULTS

A total of 2 male and 6 female patients ranging in age from 18 to 83 years (median 56, mean 54) were included. Six lacrimal apparatus MECs were found in the lacrimal gland, and 2 cases occurred in the lacrimal sac and nasolacrimal duct. Histologically, there were 6 cases of conventional MEC, 1 clear-cell variant of MEC, and 1 oncocytic variant of MEC for a total of 8 cases. There were 3 low-grade cases and 5 high-grade cases. All 8 cases were evaluated via immunohistochemistry, and the results were positive (scores 1-4) for pankeratin, 34betaE12, p63, p40, CK7, CK8, and CK19, with a relatively higher expression of p63 observed in high-grade MEC. The presence of human papillomavirus (HPV) type 6 DNA was found in 4 patients. MAML2 fluorescence in situ hybridization was positive for MAML2 rearrangement in 3 lacrimal gland tumors (2 low-grade and 1 high-grade). Six tumors were managed with radical resection, and 2 patients underwent orbital exenteration. Postoperative radiation therapy was delivered to 6 patients, and chemotherapy was administered to 1 patient.

CONCLUSIONS

MECs of the lacrimal apparatus are rare tumors, and the rate of MAML2 translocations is lower than that in salivary MECs. Lacrimal gland and lacrimal sac MECs may not be of the same subtypes intrinsically because of the difference in MAML2 translocation, anatomy, and clinical course. The etiologic function of HPV type 6 infection should be explored in lacrimal apparatus MECs. Radical surgery is the treatment of choice. The description of these unique findings may assist in the definitive diagnosis of and improve our understanding of lacrimal apparatus MEC.

Salivary gland organoid culture maintains distinct glandular properties of murine and human major salivary glands

Salivary glands that produce and secrete saliva, which is essential for lubrication, digestion, immunity, and oral homeostasis, consist of diverse cells. The long-term maintenance of diverse salivary gland cells in organoids remains problematic. Here, we establish long-term murine and human salivary gland organoid cultures. Murine and human salivary gland organoids express gland-specific genes and proteins of acinar, myoepithelial, and duct cells, and exhibit gland functions when stimulated with neurotransmitters. Furthermore, human salivary gland organoids are established from isolated basal or luminal cells, retaining their characteristics. Single-cell RNA sequencing also indicates that human salivary gland organoids contain heterogeneous cell types and replicate glandular diversity. Our protocol also enables the generation of tumoroid cultures from benign and malignant salivary gland tumor types, in which tumor-specific gene signatures are well-conserved. In this study, we provide an experimental platform for the exploration of precision medicine in the era of tissue regeneration and anticancer treatment.

MAML2-Rearranged Mucoepidermoid Carcinoma of the Parotid Gland: A Report in a 20-Month-Old Toddler

Malignancies of salivary gland origin are rare in children. Mucoepidermoid carcinoma (MEC) is the most common histologic type of salivary gland neoplasm in pediatrics. We report a rare case of parotid MEC in a 20-month-old female patient. The tumor was composed of nests of epidermoid cells with nuclei appearing vesicular, pleomorphic, and hyperchromatic with an admixture of mucous cells and cystic spaces within a prominent connective tissue stroma. Immunohistochemically, the epidermoid cells showed cytokeratin 7 and P63 positivity, and mucous cells were positive for mucicarmine. Molecularly, this case was positive for MAML2 rearrangement by FISH. To our knowledge, this is one of the youngest cases of MEC of the parotid gland reported in the English literature.

Primary mucoepidermoid carcinoma of the breast arising in adenomyoepithelioma

Mucoepidermoid carcinoma (MEC) and adenomyoepithelioma (AME) are uncommon neoplasms of the breast that are more commonly noted in the salivary glands. AMEs are benign tumours that are known to undergo malignant transformation. This report describes the first case of a MEC arising in AME in a woman in her 50s.

miR-22 and miR-205 Drive Tumor Aggressiveness of Mucoepidermoid Carcinomas of Salivary Glands

Objectives

To integrate mRNA and miRNA expression profiles of mucoepidermoid carcinomas (MECs) and normal salivary gland (NSGs) tissue samples and identify potential drivers.

Material and Methods

Gene and miRNA expression arrays were performed in 35 MECs and six NSGs.

Results

We found 46 differentially expressed (DE) miRNAs and 3,162 DE mRNAs. Supervised hierarchical clustering analysis of the DE transcripts revealed two clusters in both miRNA and mRNA profiles, which distinguished MEC from NSG samples. The integrative miRNA-mRNA analysis revealed a network comprising 696 negatively correlated interactions (44 miRNAs and 444 mRNAs) involving cell signaling, cell cycle, and cancer-related pathways. Increased expression levels of miR-205-5p and miR-224-5p and decreased expression levels of miR-139-3p, miR-145-3p, miR-148a-3p, miR-186-5p, miR-338-3p, miR-363-3p, and miR-4324 were significantly related to worse overall survival in MEC patients. Two overexpressed miRNAs in MEC (miR-22 and miR-205) were selected for inhibition by the CRISPR-Cas9 method. Cell viability, migration, and invasion assays were performed using an intermediate grade MEC cell line. Knockout of miR-205 reduced cell viability and enhanced ZEB2 expression, while miR-22 knockout reduced cell migration and invasion and enhanced ESR1 expression. Our results indicate a distinct transcriptomic profile of MEC compared to NSG, and the integrative analysis highlighted miRNA-mRNA interactions involving cancer-related pathways, including PTEN and PI3K/AKT.

Conclusion

The in vitro functional studies revealed that miR-22 and miR-205 deficiencies reduced the viability, migration, and invasion of the MEC cells suggesting they are potential oncogenic drivers in MEC.

Establishment of a patient‑derived mucoepidermoid carcinoma cell line with the CRTC1‑MAML2 fusion gene

Mucoepidermoid carcinoma (MEC) is the most common malignant tumor of the major and minor salivary glands. Surgical resection is the only curative treatment and there is no effective post-operative therapy for MEC. The present study reports an Institutional Review Board-approved case of a 45-year-old Japanese female diagnosed with low-grade MEC in the hard palate. Radical resection, supraomohyoid neck dissection and antero-lateral thigh flap reconstruction was performed. A MEC cell line was then established from the resected tumor tissue. Short tandem repeat profiling confirmed the origin and authenticity of the cell line, that harbors a CRTC1-MAML2 translocation, which is frequently observed in MEC. Amphiregulin (AREG), identified as one of the targets of the CRTC1-MAML2 fusion gene, was expressed in the cell line. The AREG receptor, epidermal growth factor receptor (EGFR) was also highly phosphorylated. The results predicted that AREG-EGFR signaling, which is required for tumor growth and survival, might be activated in the cell line in a cell-autonomous manner. As AREG expression is associated with EGFR-targeted drug resistance, this cell line might assist with the identification of novel strategies for MEC treatment.

Primary mucoepidermoid carcinoma of the intrahepatic bile duct: A case report

Mucoepidermoid carcinoma (MEC) is the most common salivary gland carcinoma; however, hepatobiliary MEC is extremely rare. A 74-year-old patient was diagnosed with hepatobiliary MEC after hepatectomy. We considered its origin could be the peribiliary glands. Its genome profile was similar to salivary MEC rather than standard biliary tract carcinoma.

KMT2A-MAML2 rearrangement emerged and regressed during neuroblastoma therapy without leukemia after 12.8-year follow-up

Twelvepatients without therapy-related leukemia were studied after completing TOP2 poison chemotherapy in a high-risk neuroblastoma regimen. One patient harbored an inv(11) that was a KMT2A rearrangement. The KMT2A-MAML2 transcript was expressed at low level. The patient was prospectively followed. The inv(11) was undetectable in ensuing samples. Leukemia never developed after a 12.8-year follow-up period. Enriched etoposide-induced TOP2A cleavage in the relevant MAML2 genomic region supports a TOP2A DNA damage mechanism. After completing TOP2 poison chemotherapies, covert KMT2A-R clones may occur in a small minority of patients; however, not all KMT2A rearrangements herald a therapy-related leukemia diagnosis.

Salivary mucoepidermoid carcinoma: Histological variants, grading systems, CRTC1/3-MAML2 fusions, and clinicopathological features

AIM

To investigate the histological diversity of salivary mucoepidermoid carcinoma (MEC), its clinicopathological features, and its associations with CRTC1/3-MAML2 fusions.

METHODS

Salivary MEC cases (n=177) were examined for CRTC1/3-MAML2, histological variants were classified, and tumors were graded according to four different grading systems. Adverse histological features considered unusual in MEC were also investigated.

RESULTS

Of the 177 MEC cases, 110 were positive for CRTC1/3-MAML2. The classical variant was most frequent in the fusion-positive, fusion-negative, and all case groups. Clear/oncocytic variant was the second most frequent in the fusion-positive and total case groups. Oncocytic, Warthin-like, and spindle variants were recognized in the fusion-positive group only. Clear cell, sclerosing, mucinous, and central variants were recorded in both fusion-positive and fusion-negative groups. No case was classified as a ciliated variant, as a mucoacinar variant, or as a high-grade transformation. Compared with the classical variant, non-classical variants were characterized by frequent CRTC1/3-MAML2 fusions and a lower clinical stage in all cases. Of four histological features considered unusual in MEC, marked nuclear atypia, frequent mitoses (>10/10HPFs), and extensive necrosis were found independently of the fusion status, and accounted for 3-5% of all cases. However, none of the cases showed overt keratinization. On comparison, the AFIP and modified Healey grading systems downgraded tumors, the Brandwein system upgraded tumors, and the Memorial Sloan Kettering system provided a moderate means of assessment.

CONCLUSION

Recognition of the histological diversity of MEC, its clinicopathological features, and its associations with CRTC1/3-MAML2 fusions is helpful for an accurate diagnosis of this carcinoma.

Mucoepidermoid carcinoma of the head and neck: CRTC1/3 MAML 2 translocation and its prognosticators

PURPOSE

Mucoepidermoid carcinoma (MEC) of the head and neck is a prevalent malignant salivary gland tumour with a reported good outcome. The aim of this study was to report the outcome in our centre.

METHODS

A retrospective chart analysis with survival analyses was performed combined with fluorescence in situ hybridization (FISH) analysis to assess CRTC1/3 MAML 2 fusion gene presence.

RESULTS

Sixty-four cases of MEC were identified. Median age at presentation was 51.4 years with a predominance for parotid gland involvement. Five, 10- and 20- year disease-free survival was 98%, 90% and 68%, respectively. Overall survival was 94%, 90% and 64%, respectively. Local recurrence was seen up to 14 years after primary diagnosis; distant metastases were diagnosed up to 17 years later. The overall recurrence rate was less than 20 per cent. CRTC1/3 MAML 2 fusion gene presence showed no survival benefit.

CONCLUSION

MEC of the head and neck has a favorable outcome with the exception of high-grade MEC. PNI and nodal involvement are not rare. CRTC1/3 MAML 2 fusion gene presence showed no survival benefit. The tendency for late onset of loco-regional and distant recurrence should not be underestimated.

Molecular Alterations in Pediatric Solid Tumors

Pediatric tumors can be divided into hematologic malignancies, central nervous system tumors, and extracranial solid tumors of bone, soft tissue, or other organ systems. Molecular alterations that impact diagnosis, prognosis, treatment, and familial cancer risk have been described in many pediatric solid tumors. In addition to providing a concise summary of clinically relevant molecular alterations in extracranial pediatric solid tumors, this review discusses conventional and next-generation sequencing-based molecular techniques, relevant tumor predisposition syndromes, and the increasing integration of molecular data into the practice of diagnostic pathology for children with solid tumors.

Targeted RNA sequencing in the routine clinical detection of fusion genes in salivary gland tumors

Salivary gland tumors represent a diverse group of neoplasms that occasionally pose a diagnostic challenge for pathologists, particularly with limited sampling. Gene fusions, which may reflect genetic drivers, are increasingly recognized in a subset of these neoplasms, and can be leveraged for diagnostic purposes. We performed a retrospective analysis on a cohort of 80 benign and malignant salivary gland tumors, enriched for subtypes known to harbor recurrent fusion events, to validate the diagnostic use of a targeted RNA sequencing assay to detect fusion transcripts. Testing identified fusion genes in 71% (24/34) of pleomorphic adenoma and carcinoma-ex-pleomorphic adenoma, with 56% of cases showing rearrangement of PLAG1 and 15% HMGA2. In addition to confirming known partners for these genes, novel PLAG1 fusion partners were identified, including DSTN, NTF3, and MEG3; CNOT2 was identified as a novel fusion partner for HMGA2. In adenoid cystic carcinoma, 95% of cases (19/20) were positive for a fusion event. MYB was rearranged in 60% (12/20), MYBL1 in 30% (6/20), and NFIB in 5% (1/20); two tumors exhibited novel fusion products, including NFIB-TBPL1 and MYBL1-VCPIP1. Fusion genes were identified in 64% (9/14) of cases of mucoepidermoid carcinoma; MAML2 was confirmed to partner with either CRTC1 (43%) or CRTC3 (21%). One salivary duct carcinoma was found to harbor a novel RAPGEF6-ACSL6 fusion gene. Finally, as anticipated, gene fusions were not detected in any of the five acinic cell carcinomas included in the cohort. In summary, targeted RNA sequencing represents a diagnostically useful ancillary technique for identifying a variety of existing, and novel, fusion transcripts in the classification of salivary gland neoplasms.

Mucoepidermoid carcinoma of the salivary glands revisited with special reference to histologic grading and CRTC1/3-MAML2 genotyping

Mucoepidermoid carcinoma (MEC) is the most common carcinoma of the salivary glands. Here, we have used two large patient cohorts with MECs comprising 551 tumors to study clinical, histological, and molecular predictors of survival. One cohort (n = 167), with known CRCT1/3-MAML2 fusion status, was derived from the Hamburg Reference Centre (HRC; graded with the AFIP and Brandwein systems) and the other (n = 384) was derived from the population-based Cancer Registry of North Rhine-Westphalia (LKR-NRW; graded with the AFIP system). The reliability of both the AFIP and Brandwein grading systems was excellent (n = 155). The weighted kappa for inter-rater agreement was 0.81 (95% CI 0.65-0.97) and 0.83 (95% CI 0.71-0.96) for the AFIP and Brandwein systems, respectively. The 5-year relative survival was 79.7% (95% CI 73.2-86.2%). Although the Brandwein system resulted in a higher rate of G3-MECs, survival in G3-tumors (AFIP or Brandwein grading) was markedly worse than in G1/G2-tumors. Survival in > T2 tumors was markedly worse than in those with lower T-stage. Also, fusion-negative MECs had a worse 5-year progression-free survival. The frequency of fusion-positive MECs in the HRC cohort was 78.4%, of which the majority (86.7%) was G1/G2-tumors. In conclusion, the AFIP and Brandwein systems are useful in estimating prognosis and to guide therapy for G3-MECs. However, their significance regarding young age (≤ 30 years) and location-dependent heterogeneity of in particular G2-tumors is more questionable. We conclude that CRTC1/3-MAML2 testing is a useful adjunct to histologic scoring of MECs and for pinpointing tumors with poor prognosis with higher precision, thus avoiding overtreatment.

Mucoepidermoid carcinoma of the parotid gland: Twenty-year experience in treatment and outcomes

BACKGROUND

Parotid gland mucoepidermoid carcinoma (MEC) has published five-year cancer-specific survival (CSS) rates of 77%-97%, with variance related to grade.

METHODS

Patients receiving primary surgery for parotid gland MEC from 1995 to 2014 at a tertiary medical center underwent clinical review, histopathologic review, and cytogenetic analysis. Survival outcomes were evaluated.

RESULTS

Among 58 patients, T/N/M classification was as follows: T1 in 35 patients, T2 in 14, T4a in 9, N0 in 53, N1 in 2, N2b in 3. Histologic grade was low in 27, intermediate in 17, and high in 12 patients with 98% MAML2 positivity. All patients underwent parotidectomy, and seven patients received adjuvant radiation therapy. CSS was 100% at 5 years and 94.1% at 10 and 15 years. Two patients experienced locoregional recurrence.

CONCLUSIONS

Treatment with adequate surgical resection and adjuvant radiation therapy for high-grade or advanced-stage tumors yields excellent survival, independent of clinical stage or pathologic grade.

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.

Molecular Profiling of Salivary Oncocytic Mucoepidermoid Carcinomas Helps to Resolve Differential Diagnostic Dilemma With Low-grade Oncocytic Lesions

Oncocytic mucoepidermoid carcinoma (OMEC) is a rare but diagnostically challenging variant of mucoepidermoid carcinoma (MEC). OMEC is notable for differential diagnostic considerations that are raised as a result of overlap with other benign and low-grade oncocytic salivary gland tumors. Diffuse and strong immunoreactivity of p63 protein may be useful in distinguishing OMEC from its mimics. However, focal p63 staining can be present in benign oncytomas. Presence of mucin-containing cells, mucinous cystic formation, and foci of extravasated mucin are considered a hallmark of MEC. True mucocytes may be, however, very few and hardly discernable in OMECs. Recent evidence has shown that most MECs harbor gene fusions involving MAML2. A retrospective review of archived pathology files and the authors' own files was conducted to search for "low-grade/uncertain oncocytic tumor," "oncocytoma," and "oncocytic carcinoma" in the period from 1996 to 2019. The tumors with IHC positivity for p63 and/or p40, and S100 negativity, irrespective of mucicarmine staining, were tested by next-generation sequencing using fusion-detecting panels to detect MAML2 gene rearrangements. Two index cases from consultation practice (A.S. and A.A.) of purely oncocytic low-grade neoplasms without discernible mucinous cells showed a CRTC1-MAML2 fusion using next-generation sequencing, and were reclassified as OMEC. In total, 22 cases of oncocytic tumors, retrieved from the authors' files, and from the Salivary Gland Tumor Registry, harbored the MAML2 gene rearrangements. Presence of mucocytes, the patterns of p63 and SOX10 immunopositivity, and mucicarmine staining were inconsistent findings. Distinguishing OMEC devoid of true mucinous cells from oncocytoma can be very challenging, but it is critical for proper clinical management. Diffuse and strong positivity for p63 and visualization of hidden mucocytes by mucicarmine staining may be misleading and does not always suffice for correct diagnosis. Our experience suggests that ancillary studies for the detection of MAML2 rearrangement may provide useful evidence in difficult cases.

Prognostic impact of CRTC1/3-MAML2 fusions in salivary gland mucoepidermoid carcinoma: A multiinstitutional retrospective study

Mucoepidermoid carcinoma (MEC) is rare, but the most common primary malignancy of the salivary gland and not infrequent in young individuals. CRTC1/3-MAML2 fusions are frequently detected in MEC and are useful as a diagnostic biomarker. However, there has been debate as to whether the fusions have prognostic significance. In this study, we retrospectively collected 153 salivary gland MEC cases from 11 tertiary hospitals in Japan. As inclusion criteria, the MEC patients in this study had curative surgery as the initial treatment, received no preoperative treatment, and had no distant metastasis at the time of the initial surgery. The MEC diagnosis was validated by a central pathology review by five expert salivary gland pathologists. The CRTC1/3-MAML2 fusions were detected using FISH and RT-PCR. In 153 MEC cases, 90 (58.8%) were positive for CRTC1/3-MAML2 fusions. During the follow-up period, 28 (18.3%) patients showed tumor recurrence and 12 (7.8%) patients died. The presence of the fusions was associated with favorable tumor features. Of note, none of the fusion-positive patients died during the follow-up period. Statistical analysis showed that the presence of the fusions was a prognostic indicator of a better overall survival in the total and advanced-stage MEC cohorts, but not in the early-stage MEC cohort. In conclusion, CRTC1/3-MAML2 fusions are an excellent biomarker for favorable overall survival of patients with salivary gland MEC.

Conjunctival 'mucoepidermoid carcinoma' revisited: a revision of terminology, based on morphologic, immunohistochemical and molecular findings of 14 cases, and the 2018 WHO Classification of Tumours of the Eye

In 2018, the consensus meeting for the WHO Classification of Tumours of the Eye decided that conjunctival mucoepidermoid carcinoma should be reclassified as adenosquamous carcinoma, as this represented a better morphological fit. To examine the applicability of this terminology, we studied the clinical, histopathological, immunohistochemical and molecular pathology of 14 cases that were originally diagnosed as conjunctival mucoepidermoid carcinoma. There were 7 (50%) females and 7 (50%) males. The median age was 64 years. The left eye was affected in 8 and the right eye in 6 patients. In-situ carcinoma was present in 11/14 (79%) cases and comprised in-situ squamous cell carcinoma (SCC) and conjunctival intraepithelial neoplasia with mucinous differentiation (CIN-Muc). Invasive carcinoma was present in 11/14 (79%) cases. Group 1 (1/11 cases, 9%) comprised invasive SCC only. Group 2 (6/11 cases, 55%) comprised SCC with mucinous differentiation, manifesting as scattered intracellular mucin, occasionally together with intercellular mucin, with no evidence of true glandular differentiation. Group 3 (3/11 cases. 27%) comprised true adenosquamous carcinoma. Group 4 (1/11 cases, 9%) comprised pure adenocarcinoma. Thirteen of 14 cases (93%) underwent FISH for MAML2 translocation and none were rearranged. Two cases harboured high-risk HPV (type 16 and 18). The combined findings confirm that all lesions in our study were not mucoepidermoid carcinoma, but represented predominantly SCC with mucinous differentiation and adenosquamous carcinoma. We, therefore, recommend future revision of the WHO classification to include SCC with mucinous differentiation alongside adenosquamous carcinoma.

FGFR4 Gly388Arg Polymorphism Affects the Progression of Gastric Cancer by Activating STAT3 Pathway to Induce Epithelial to Mesenchymal Transition

Purpose

Fibroblast growth factor receptor 4 (FGFR4) plays a critical role in cancer progression involving in tumor proliferation, invasion, and metastasis. This study clarified the role of FGFR4-Arg388 variant in gastric cancer (GC), and more importantly highlighted the possibility of this single nucleotide polymorphism (SNP) as potential therapeutic targets.

Materials and Methods

FGFR4 polymorphism was characterized in advanced GC patients to perform statistical analysis. FGFR4-dependent signal pathways involving cell proliferation, invasion, migration, and resistance to oxaliplatin (OXA) in accordance with the SNP were also assessed in transfected GC cell lines.

Results

Among 102 GC patients, the FGFR4-Arg388 patients showed significantly higher tumor stage (p=0.047) and worse overall survival (p=0.033) than the Gly388 patients. Immunohistochemical results showed that FGFR4-Arg388 patients were more likely to have higher vimentin (p=0.025) and p-STAT3 (p=0.009) expression compared with FGFR4-Gly388 patients. In transfected GC cells, the overexpression of FGFR4-Arg388 variant increased proliferation and invasion of GC cells, increasing resistance of GC cells to OXA compared with cells overexpressing the Gly388 allele.

Conclusion

The exploration mechanism may be through FGFR4-Arg388/STAT3/epithelial to mesenchymal transition axis regulating pivotal oncogenic properties of GC cells. The FGFR4-Arg388 variant may be a biomarker and a candidate target for adjuvant treatment of GC.

Clinicopathological significance of EGFR pathway gene mutations and CRTC1/3-MAML2 fusions in salivary gland mucoepidermoid carcinoma

AIMS

Mucoepidermoid carcinoma (MEC) is one of the most common salivary gland carcinomas. Epidermal growth factor receptor (EGFR) signalling pathway gene mutations are important in predicting a patient's prognosis, selecting molecularly targeted drugs and estimating the efficacy of a molecular therapy. However, their significance in MEC have been poorly clarified. CRTC1/3-MAML2 fusions are specific to MEC and may be associated with favourable characteristics in these patients.

METHODS AND RESULTS

We looked for CRTC1/3-MAML2 fusions and gene alterations in the EGFR, RAS family (KRAS, HRAS and NRAS), PIK3CA, BRAF and AKT1 in 101 MEC cases. We also examined mutations in TP53. CRTC1/3-MAML2 fusions were found in 62.4% of the cases. KRAS, HRAS and PIK3CA mutations were detected in 6.9%, 2.0% and 6.9%, respectively, but other EGFR pathway genes were not mutated. In total, gene mutations (RAS/PIK3CA) in the EGFR pathway were detected in 14.9% of the cases. TP53 mutations were found in 20.8%. CRTC1/3-MAML2 fusions were associated with a better prognosis and RAS/PIK3CA mutations a worse prognosis of the patients, respectively, and both were selected as independent prognostic factors for the overall survival of the patients. TP53 mutations had no prognostic impact. CRTC1/3-MAML2 fusion-positive rates were inversely associated with the patients' age and the fusions were found in 82% of patients aged < 30 years.

CONCLUSIONS

RAS/PIK3CA mutations were frequently detected, and may be a biomarker for a poorer prognosis in MEC patients. CTRC1/3-MAML2 fusions were positive in most of the young MEC patients.

Intra-Cystic (In Situ) Mucoepidermoid Carcinoma: A Clinico-Pathological Study of 14 Cases

AIMS

To report on the clinico-pathological features of a series of 14 intra-oral mucoepidermoid carcinomas showing exclusive intra-cystic growth.

Materials and methods

All mucoepidermoid carcinomas diagnosed in the period 1990–2012 were retrieved; the original histological preparations were reviewed to confirm the diagnosis and from selected cases, showing exclusive intra-cystic neoplastic components, additional sections were cut at three subsequent 200 m intervals and stained with Hematoxylin–Eosin, PAS, Mucicarmine and Alcian Blue, to possibly identify tumor invasion of the adjacent tissues, which could have been overlooked in the original histological preparations. Additionally, pertinent findings collected from the clinical charts and follow-up data were analyzed.

Results

We identified 14 intraoral mucoepidermoid carcinomas treated by conservative surgery and with a minimum follow up of five years. The neoplasms were located in the hard palate (nine cases), the soft palate (two), the cheek (two) and the retromolar trigone (one). In all instances, histological examination revealed the presence of a single cystic space, containing clusters of columnar, intermediate, epidermoid, clear and mucous-producing cells, the latter exhibiting distinct intra-cytoplasmic mucin production, as confirmed by PAS, Mucicarmine and Alcian Blue stains. The cysts were entirely circumscribed by fibrous connective tissue, and no solid areas or infiltrating tumor cell clusters were detected. Conservative surgical resection was performed in all cases, and no recurrences or nodal metastases were observed during follow up.

Conclusions

Mucoepidermoid carcinomas showing prominent (>20%) intra-cystic proliferation currently are considered low-grade tumors. In addition, we also unveil the possibility that mucoepidermoid carcinomas, at least in their early growth phase, may display an exclusive intra-cystic component and might be considered as in situ carcinomas, unable to infiltrate adjacent tissues and metastasize.

MAML2 rearrangement as a useful diagnostic marker discriminating between Warthin tumour and Warthin-like mucoepidermoid carcinoma

Warthin tumour is the second most common benign neoplasm of salivary glands. Despite its relatively characteristic histology, it may sometimes mimic other lesions. Here, we report two female non-smoker patients diagnosed with low-grade mucoepidermoid carcinoma with oncocytic epithelium and prominent lymphoid (Warthin-like) stroma and with molecularly confirmed MAML2 rearrangement. In addition, we screened a consecutive series of 114 Warthin tumour cases by means of MAML2 break apart fluorescence in situ hybridization to assess its value in differential diagnosis. MAML2 rearrangement was detected in both mucoepidermoid carcinoma cases, while all Warthin tumours were negative. Taking into account the literature data, Warthin-like mucoepidermoid carcinomas are more frequently observed in women, while a slight male predominance and smoking history are typical for Warthin tumour. In addition, the patients with Warthin-like mucoepidermoid carcinoma were significantly younger than those with Warthin tumour. To conclude, Warthin-like mucoepidermoid carcinoma may usually be suspected based on histology, while the diagnosis can be confirmed by means of molecular assays such as FISH. The investigation of MAML2 status is particularly advised when Warthin tumour is considered in a young, non-smoking, female patient.

The significance of mucinous metaplasia in Warthin tumor: a frequent occurrence and potential pitfall

Mucinous metaplasia in Warthin tumor (WT) is a recognized phenomenon. Nevertheless, its presence can create a diagnostic challenge in the distinction from the newly proposed variant of mucoepidermoid carcinoma (MEC), Warthin-like MEC. In this study, we evaluated the significance and diagnostic relevance of mucinous metaplasia in WTs. A total of 30 WTs diagnosed based on resection specimens formed the basis of this retrospective study. Mucicarmine staining was performed to identify mucinous metaplasia, and fluorescence in situ hybridization (FISH) analysis was used to detect MAML2 gene rearrangement. After review, one MAML2 rearranged case was reclassified as Warthin-like MEC as the classic bilayered epithelium in WT was not identified. The diagnosis of WT was confirmed in the remaining 29 cases. Mucinous metaplasia was encountered in 24 WTs (83%), with 14% (4/29) having an abundant amount. We found that mucinous metaplasia correlated with tumor size (p < 0.05). Age and sex distribution were similar in WT cases with or without mucinous metaplasia. In addition, neither the presence of squamous metaplasia nor the time interval between fine-needle aspiration and surgery was related to mucinous metaplasia (p > 0.05). The MAML2 FISH analyses performed in 18 WTs with variable amounts of mucinous metaplasia were negative for rearrangement. In conclusion, mucinous metaplasia is fairly common in WTs and shows a significant correlation with tumor size. Therefore, caution should be taken to avoid overinterpretation of WT with mucinous metaplasia as MEC in cases showing the classic bilayered oncocytic lining epithelium.

Mucoepidermoid Carcinoma: A Comparison of Histologic Grading Systems and Relationship to MAML2 Rearrangement and Prognosis

Mucoepidermoid carcinoma (MEC) is the most common salivary gland malignancy, but categorization is complicated by variability in grading systems and uncertain prognostic significance of MAML2 rearrangement. The aims of this study were to determine the prognostic significance of MEC grading systems and MAML2 rearrangement status. Fifty-three carcinomas originally diagnosed as MEC (45 primary; 8 recurrent) of major and minor salivary glands were graded according to modified Healey, Brandwein, AFIP, and Katabi systems. Fluorescence in situ hybridization for MAML2 rearrangement was performed. Clinical features and outcomes were recorded. Twenty-five (47%) carcinomas scored the same in all grading systems. The most common histologic feature leading to a diagnosis of intermediate grade was isolated solid growth. Brandwein assigned the highest percentage of high grade (29%) and AFIP the highest percentage of low grade (80%). MAML2 was rearranged in 37/46 (80%) cases. Forty-three (81%) were morphologically compatible with MEC, and these were more likely to be low-intermediate grade and MAML2-rearranged. Of primary carcinomas, 6 (13%) recurred. Statistically significant univariate risk factors for recurrence included non-MEC morphology, stage T4, and high Brandwein grade. Margin status, MAML2 rearrangement, and isolated solid growth were not predictive of recurrence. A binary grading system (Brandwein high vs. low-plus-intermediate) could be considered to better reflect biological behavior in MEC. Our study confirms that MAML2 wildtype tumors more likely represent high grade non-MECs, and prior studies demonstrating worse prognosis in MAML2-nonrearranged MECs may be diluted by high-grade non-MECs.

Pathologic grading of mucoepidermoid carcinomas of the salivary gland and its effect on clinicopathologic follow-up: an institutional experience

Mucoepidermoid carcinoma (MEC) is the most common malignant salivary gland tumor. Differences inprognosis can be noted owing to the tumor grade determined using multiple grading schemes (2-tier: low- and high-grade vs. 3-tier: low-, intermediate-, and high-grade). We studied clinicopathologic features of MEC using a 3-tier grading system and retrospectively categorized cytologic diagnoses as per the Milan System for Reporting Salivary Gland Cytopathology (MSRSGC).A total of 69 cases of MEC were identified, and most were seen in the parotid gland. Aggressive clinical behavior was seen in high-grade MEC compared with intermediate- and low-grade MEC. By fluorescence in situ hybridization (FISH) analysis, MAML2 rearrangements were seen in 78% of cases.The MSRSGC subcategorized the majority (63.8%) of MEC as salivary gland neoplasm of uncertain malignant potential, suspicious for malignancy, or malignant. Clustering intermediate- with low-grade cases did not significantly impact the clinical behavior. Both high-grade and oncocytic MEC can be MAML2 FISH negative.

Prognostic value of CRTC1-MAML2 translocation in salivary mucoepidermoid carcinoma: Systematic review and meta-analysis

The presence of the CRTC1-MAML2 translocation has been described in mucoepidermoid carcinoma (MEC) as a predictor of better survival rates. However, the real prognostic value of the translocation has been debated due to recent controversial findings. The aim of this study was to perform a systematic review to understand the prognostic potential of the CRTC1-MAML2 translocation in MEC. An electronic search was carried out using the MEDLINE/PubMed, EMBASE and Scopus databases. Articles that assessed the association between the CRTC1-MAML2 translocation and survival of MEC patients were selected for the systematic review. Ten published articles were included in the qualitative synthesis. The prevalence of the translocation varied from 33.7% to 69.7%. Seven studies observed a significant association between the presence of the CRTC1-MAML2 translocation and a favourable clinical outcome, which could improve disease-free, disease-specific or overall survival. Five studies were included in the quantitative synthesis. Fixed-effects model confirmed that translocation-positive patients have a decreased risk of death (combined odds ratio 0.08, 95% confidence interval - 0.03-0.23, P < .00001). The detection of the CRTC1-MAML2 translocation appears to be useful as a prognostic factor in MEC. However, the level of evidence is not as high as it could be once important limitations were found in the published studies.

Assessing the prognostic significance of MUC4β in mucoepidermoid carcinoma of the salivary glands: An immunohistochemical study

Objectives

– Routine histopathological grading for salivary gland mucoepidermoid carcinoma (MEC) have failed to prognosticate these tumors, resulting in poor post-surgical outcomes. In developing countries, the lack of technologically advanced infrastructure curtails, efficient treatment modalities. This study aimed at determining if MUC4β can characterize salivary gland MEC and serve as a practical and inexpensive method to prognosticate salivary gland MEC.

Materials and methods

– Fifteen cases of archived paraffin embedded tissue blocks of mucoepidermoid carcinomas were reassessed for histopathological grading using Healey's system, modified by Batsakis and Luna and immunohistochemically evaluated for expression of MUC4β. Statistical analysis (Kappa statistics and Spearman's rho correlation coefficient) was performed to assess inter-observer reproducibility and to correlate the expression of MUC4β with the histopathological grade of the tumor.

Results

MUC4β expression is related to tumor differentiation in an inverse relationship. Two cases of high grade MEC were the exception to this rule.

Conclusion

Our study revealed that MUC4β alone cannot serve as a reliable prognostic marker due to its divergent tumor suppressor and oncogenic pathway. The role of MUC4β needs further evaluation and research so as to potentiate therapeutics depending upon its context dependent function, as a cancer marker or an oncogenic factor.

"Pancreatic Mucoepidermoid Carcinoma" Is not a Pancreatic Counterpart of CRTC1/3-MAML2 Fusion Gene-related Mucoepidermoid Carcinoma of the Salivary Gland, and May More Appropriately be Termed Pancreatic Adenosquamous Carcinoma With Mucoepidermoid Carcinoma-like Features

"Mucoepidermoid carcinoma (MEC)" has been accepted as a synonym for pancreatic adenosquamous carcinoma (ASC). Pancreatic ASC can show salivary gland-type MEC-like morphology. CRTC1/3-MAML2 fusion gene is a characteristic molecular feature of MEC of the salivary gland. We conducted this study to clarify whether the pancreatic ASC with salivary gland-type MEC-like morphology (Pan-MEC) is a pancreatic counterpart of salivary gland-type MEC (Sal-MEC). We retrospectively analyzed 37 pancreatic ASCs including 16 Pan-MECs and 21 tumors without MEC-like features (ASC-NOS [not otherwise specified]), and we investigated (1) clinicopathologic features, (2) the presence of CRTC1/3-MAML2 fusion gene by reverse transcription polymerase chain reaction, (3) the presence of rearrangement of MAML2 gene by fluorescence in situ hybridization, and (4) mucin core proteins by immunohistochemistry. We also compared 16 Pan-MECs with 20 Sal-MECs by immunohistochemistry for mucin core protein. There were no significant differences of any clinicopathologic characteristics and survival analysis between the Pan-MECs and ASCs-NOS. Of note, the pancreatic ASCs (including Pan-MEC and ASC-NOS) were significantly more aggressive than conventional pancreatic ductal adenocarcinoma. In addition, all Pan-MECs were histologically high-grade. CRTC1/3-MAML2 fusion gene and MAML2 gene rearrangement were not detected in any ASCs including Pan-MECs. There were significant differences of MUC5AC and MUC6 between the Pan-MECs and Sal-MECs, but no significant differences of mucin core protein between the Pan-MECs and pancreatic ASCs-NOS. Pan-MEC is histologically and biologically high-grade and unrelated to CRTC1/3-MAML2 fusion gene, unlike Sal-MEC which is related to CRTC1/3-MAML2 fusion gene. Pan-MEC is not a pancreatic counterpart of CRTC1/3-MAML2 fusion gene-related Sal-MEC.

Mucoepidermoid carcinoma of the oropharynx: a tumor type with a propensity for regional metastasis unrelated to histologic grade

The designation "mucoepidermoid tumor" is a historic one used in reference to a form of mucoepidermoid carcinoma (MEC) that was believed to be benign. This bygone notion was based on the observation that the vast majority of MECs arising from the intraoral minor salivary glands behave in a benign fashion, particularly when they do not exhibit high grade features. There has been a recent move to partition the oral vault into the oral cavity proper and the oropharynx based on awareness that these compartments are distinct, and that similar tumor types arising from these compartments may behave in dramatically different ways (e.g, oral cavity squamous cell carcinoma vs oropharyngeal squamous cell carcinoma). The pathology databases from 3 large academic medical centers were searched for cases of MECs arising in the oropharynx. Relevant clinical and pathological information was collected from the medical records. Twenty-five cases were identified. They were from 18 females (72%) and 7 males (28%), ranging in age from 31 to 88 years (median, 61). Twenty-two (88%) were classified as low (n = 12) or intermediate (n = 10) grade, and 3 (12%) as high grade. Most arose from the base of tongue (n = 24), but one arose from the lateral pharyngeal wall. The median tumor size was 2.0 cm. Nineteen patients underwent neck node dissections. Of these, 13 (68%) had histologically documented lymph node metastases. MECs that lacked high grade features were almost as likely to metastasize as those with high grade features (50% vs 66%, Fisher exact = 1). Of 3 metastases tested, 2 harbored the MAML2 gene fusion. MECs arising from the base of tongue are associated with an alarmingly high rate of nodal metastases. This behavior cannot be predicted by histologic grading or MAML2 status. The propensity to metastasize may to some degree reflect the unique microenvironment of the oropharynx.

Primary mucoepidermoid carcinoma of the liver with CRTC1-MAML2 fusion: a case report

Background

CRTC1-MAML2 fusion is often detected in low- or intermediate-grade salivary mucoepidermoid carcinoma (MEC), and it is associated with a favorable clinical course. Primary MEC of the liver is an extremely rare, aggressive tumor, and no study has investigated CRTC1-MAML2 fusion.

Case presentation

A 79-year-old Japanese female presented with an approx. 5-cm hepatic mass lesion. We surgically resected the lesion under the clinical diagnosis of intrahepatic cholangiocarcinoma. The histological and immunohistochemical findings were consistent with high-grade MEC, consisting of squamoid, mucin-producing, and intermediate tumor cells. Our RT-PCR analysis revealed the presence of CRTC1-MAML2 fusion. This fusion gene was further confirmed by direct sequencing. The patient is still alive almost 10 years after the surgery.

Conclusion

This is the first case report of primary MEC of the liver with CRTC1-MAML2 fusion, with long survival. The present case has significant implications for the entity of primary MEC of the liver which should be distinguished from adenosquamous carcinoma.

The Role of Ancillary Techniques in Salivary Gland Cytopathology Specimens

Salivary gland tumor aspiration cytology is a useful preoperative test to guide the most appropriate clinical and surgical management for these patients. Although salivary gland cytology is often useful to distinguish between non-neoplastic lesions, benign neoplasms and malignant neoplasms, there remain many challenges in this area. Specifically, these tumors are uncommon and may have considerable morphologic overlap, especially in the setting of a malignant tumor. This article reviews some of the immunohistochemical and molecular characteristics of more common salivary gland neoplasms that pathologists and cytotechnologists may encounter. When used in combination with morphologic features, such ancillary testing can be useful to further refine the differential diagnosis, more strongly favor a particular entity, or in some instances confidently provide a specific diagnosis.

Immunohistochemical Assessment of BAP1 Protein in Mucoepidermoid Carcinomas

Mucoepidermoid carcinomas are common malignant salivary gland tumors. Despite recent advances in diagnosis and treatment, there has not been much improvement in outcome of these patients, necessitating identification of novel targeted therapeutic agents. Genomic profiling of mucoepidermoid carcinomas has recently revealed aberrations in BAP1 gene. Therefore, we conducted this study to identify BAP1 loss by immunohistochemistry in these tumors. Mucoepidermoid carcinoma cases were retrieved; hematoxylin-and-eosin stained sections were reviewed. Immunohistochemistry for BAP1 was performed. Forty cases were assessed, including 25 salivary gland and 15 pulmonary mucoepidermoid carcinomas. There were 19 cases in the parotid (76%), two in submandibular gland (8%), and remaining 16% from minor salivary gland locations. Ten (40%) were low grade, nine (36%) were intermediate grade, and six (24%) were high grade mucoepidermoid carcinomas. Thirteen (86.7%) pulmonary mucoepidermoid carcinomas were tracheobronchial, while two (13.3%) were intraparenchymal; all were low grade mucoepidermoid carcinomas. On immunohistochemistry, BAP1 nuclear staining was retained in all cases (100%), irrespective of tumor location or grade. Therapeutic connotations necessitate the identification of readily applicable techniques to detect BAP1 loss in mucoepidermoid carcinomas. Using immunohistochemistry, loss of BAP1 staining was not seen in any of our cases, suggesting insensitivity of BAP1 IHC to detect aberrations at genomic level in these tumors. Analysis of BAP1 alterations by targeted sequencing may therefore be performed prior to excluding the possibility of response to BAP1-targeted therapeutics based on immunohistochemistry alone.

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.

Postoperative radiotherapy for T1/2N0M0 mucoepidermoid carcinoma positive for CRTC1/3-MAML2 fusions

BACKGROUND

The National Comprehensive Cancer Network (NCCN) guidelines recommend considering postoperative radiotherapy (PORT) for completely resected T1/2N0M0 salivary mucoepidermoid carcinomas when they show tumor spillage, perineural invasion, or intermediate/high-grade histology. CRTC1/3-MAML2 fusions have been associated with a favorable clinical outcome.

METHODS

Forty-seven T1/2N0M0 mucoepidermoid carcinoma cases positive for CRTC1/3-MAML2 fusions were completely resected and were not treated with PORT.

RESULTS

Pathologically, none of the cases showed tumor spillage or perineural invasion. Cases with intermediate/high-grade histology numbered 9 (19%) to 26 (55%) with the currently used 3 different grading systems. During the follow-up (median 60 months), locoregional tumor recurrence occurred in 4 cases, which were treated with surgery alone. At the last follow-up (median 60 months; 7-160), all patients were alive with no evidence of disease.

CONCLUSION

An excellent prognosis may be achieved without PORT in T1/2N0M0 mucoepidermoid carcinoma patients positive for CRTC1/3-MAML2 fusions when the tumors are completely resected without tumor spillage.

MAML2 Rearrangements in Variant Forms of Mucoepidermoid Carcinoma: Ancillary Diagnostic Testing for the Ciliated and Warthin-like Variants

Mucoepidermoid carcinoma (MEC) is the most common salivary gland malignancy. Recent studies have shown that most MECs harbor gene fusions involving MAML2-an alteration that appears to be specific for MEC, a finding that could be diagnostically useful. While most cases of MEC are histologically straightforward, uncommon variants can cause considerable diagnostic difficulty. We present 2 variants of MEC for which MAML2 studies were crucial in establishing a diagnosis: a previously undescribed ciliated variant, and the recently described Warthin-like variant. All cases of ciliated and Warthin-like MEC were retrieved from the archives of The Johns Hopkins Hospital. Break-apart fluorescence in situ hybridization for MAML2 was performed on all cases. One ciliated MEC and 6 Warthin-like MECs were identified. The ciliated MEC presented as a 4.6 cm cystic lymph node metastasis originating from the tongue base in a 47-year-old woman. The Warthin-like MECs presented as parotid masses ranging in size from 1.2 to 3.3 (mean, 2.7 cm) in 4 women and 2 men. The ciliated MEC consisted of macrocystic spaces punctuated by tubulopapillary proliferations of squamoid cells and ciliated columnar cells. The Warthin-like MECs were comprised of cystic spaces lined by multilayered oncocytic to squamoid cells surrounded by a circumscribed cuff of lymphoid tissue with germinal centers. In these cases, the Warthin-like areas dominated the histologic picture. Conventional MEC, when present, represented a minor tumor component. MAML2 rearrangements were identified in all cases. Warthin-like MEC, and now a ciliated form of MEC, are newly described variants of a common salivary gland carcinoma. Unfamiliarity with these novel forms, unanticipated cellular features (eg, cilia), and morphologic overlap with mundane benign processes (eg, developmental ciliated cysts, Warthin tumor) or other carcinomas (eg, ciliated human papillomavirus-related carcinoma) may render these variants susceptible to misdiagnosis. These unusual variants appear to consistently harbor MAML2 fusions-a finding that establishes a clear link to conventional MEC and provides a valuable adjunct in establishing the diagnosis.

Central mucoepidermoid carcinoma arising from glandular odontogenic cyst confirmed by analysis of MAML2 rearrangement: A case report

Central mucoepidermoid carcinoma (MEC) poses a diagnostic challenge because of its rarity and histological overlap with glandular odontogenic cyst (GOC). In MEC of both salivary glands and jaws, MAML2 arrangement has been well known as the specific gene alteration. We report a case of central MEC arising from GOC diagnosed by MAML2 fusion gene. A 57-year-old male presented a multilocular cystic lesion in left molar region of the mandible. Histopathologically, multiple cysts lined by thin cuboidal or non-keratinized squamous epithelium with small duct-like structures, mucous cells and ciliated cells were present. It was diagnosed as GOC. The recurrent lesion after nine years showed the proliferation of many cystic and solid nests composed of epidermoid, mucous and intermediated cells. Nested PCR revealed CRTC3-MAML2 fusion gene in the recurrent lesion, but not in the primary one. Similarly, MAML-2 rearrangement by FISH analysis was positive in the recurrent lesion, while negative for the primary one, thus confirming the diagnosis of central MEC arising from GOC. Analysis of MAML2 rearrangement can be used as a supportive evidence to distinguish central MEC from GOC.

Prognostic factors in head and neck mucoepidermoid carcinoma: experience at a single institution based on 64 consecutive patients over a 28-year period

Mucoepidermoid carcinoma (MEC) is the most common malignancy of the salivary glands. The clinical behaviour of MEC is largely unpredictable, ranging from indolent tumour growth to highly aggressive metastatic spread. The objective of this study was to determine the clinicopathological predictors of recurrence and survival in patients with head and neck MEC. The medical records of 64 patients who underwent surgical treatment for head and neck MEC between 1982 and 2010 were reviewed. The main outcome measures were disease-free survival (DFS) and overall survival (OS). Clinicopathological parameters evaluated were age, sex, anatomical subsite, histological grade, tumour stage, tumour size, adjuvant therapy, and nodal and margin status. For the entire cohort, the 5-year DFS was 82.8% and the 5-year OS was 67.2%. Histological grade and tumour subsite were statistically significant predictors of OS. Furthermore, tumour stage and nodal status were statistically significant predictors with respect to OS. Advanced tumour stage, high histological grade, submandibular/sublingual localization, and positive nodal status were independent predictors of the prognosis in patients with head and neck MEC. Further studies into the molecular biology of MEC are needed in order to provide new therapeutic strategies for patients with locally aggressive and highly metastatic carcinomas.

Primary paranasal sinus hyalinizing clear cell carcinoma: a case report

Background

Hyalinizing clear cell carcinoma (HCCC) is a rare low-grade tumour of salivary glands that was first described as a distinct entity in 1994 by Milchgrub et al. EWSR1-ATF1 fusion was found to be specific for this tumour. The majority of the reported cases of HCCC arise from minor salivary glands within the oral cavity. Primary HCCC of the paranasal sinus is extremely uncommon. To our knowledge, only three cases have been reported in the English literature. Herein, we present a case of HCCC of the posterior ethmoid/maxillary sinus.

Case presentation

A 63-year-old lady who presented with a long history of epistaxis. CT scan revealed a destructive mass in the left ethmoid/posterior maxillary sinus extending to the nasal cavity. Surgical excision was done and microscopic evaluation showed a tumour composed mainly of nests of clear epithelial cells separated by fibrocellular and hyalinized septa with extensive bone destruction. The tumour cells expressed CK5/6, EMA and p63 immunohistochemically but were negative for S100 protein, PAX-8, RCC and CK7. Sinonasal renal cell–like adenocarcinomas, myoepithelial carcinoma and metastatic renal cell carcinoma were excluded by radiological and immunohistochemical studies. Fluorescence in situ hybridization analysis revealed an EWSR1 gene rearrangement. Postoperative radiation was administrated and the patient did not show recurrence or distant metastasis 4 months after the surgery.

Conclusion

Head and neck region have many tumours that demonstrate clear cell changes on histology. Thus, the differential diagnosis for HCCC is wide. Awareness of this rare entity and the possibility of it is arising in unusual location is necessary. EWSR1-AFT1 fusion, a consistent finding in HCCC, can be used to confirm the diagnosis.

IL-6/STAT3/TWIST inhibition reverses ionizing radiation-induced EMT and radioresistance in esophageal squamous carcinoma

The acquisition of radioresistance by esophageal squamous carcinoma (ESC) cells during radiotherapy may lead to cancer recurrence and poor survival. Previous studies have demonstrated that ionizing radiation (IR) induces epithelial–mesenchymal transition (EMT) of ESC cells accompanied by increased migration, invasion, and radioresistance. However, the underlying molecular mechanisms of IR-induced EMT and radioresistance are not well established, hampering the development of potential solutions. To address this issue, we investigated the role of the IL-6/STAT3/TWIST signaling pathway in IR-induced EMT. We found not only the pathway was activated during IR-induced EMT but also STAT3 inhibition or Twist depletion reversed the EMT process and attenuated radioresistance. These results improve our understanding of the underlying mechanisms involved in IR-induced EMT and suggest potential interventions to prevent EMT-induced acquisition of radioresistance.