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

Parotid Gland Tumors: Molecular Diagnostic Approaches

Parotid gland pathology represents a web of differential diagnoses. There are many complex cases that require extensive diagnostic tests for a complete and correct final pathology diagnosis. Currently the official classification of parotid gland tumors extends over more than 40 subtypes. We performed a query of the PubMed database regarding the use of molecular biology tests in performing a better characterization of the tumors in specific cases. By using fluorescence in situ hybridization (FISH), reverse transcription polymerase chain reaction (RT-PCR) or next-generation sequencing, the team managing complex cases can offer a personalized therapeutic solution. We review the molecular differential diagnosis according to published articles in the last 5 years for many types of parotid gland tumors ranging from benign to borderline malign tumors to malign aggressive tumors. Mucoepidermoid carcinoma is a distinct subtype of parotid malignancy that was the subject of a consistent number of articles. However, the molecular biology diagnosis techniques helped more in excluding the diagnosis of mucoepidermoid carcinoma, and probably retrospectively limiting the number of cases with this final diagnosis. In Romania, the molecular biology diagnosis is available only in limited research facilities and should receive more consistent funding that will make it available on a larger scale. The novelty of this scoping review is that we propose an algorithm for molecular differential diagnosis of the tumors that could be encountered in the parotid gland.

Expanding the cytological and architectural spectrum of mucoepidermoid carcinoma: The key to solving diagnostic problems in morphological variants

Mucoepidermoid carcinoma (MEC) is the most common malignant salivary gland tumor. Varying sized cysts and sheets composed of three cell types (epidermoid, intermediate, and mucous cells) with varying degrees of atypia form the characteristic histological appearance of MEC. MEC frequently contains a wide variety of modified tumor cells and can be entirely cystic or completely solid. Under these circumstances, MEC requires critical differentiation from many mimickers, ranging from simple cysts and benign tumors to high-grade carcinomas. Tumor-associated lymphoid proliferation and sclerotic changes in the stroma also contribute to diagnostic difficulties. Several well-known diagnostically challenging variants (oncocytic, clear cell, spindle cell, and sclerosing) exist in MEC. With the advent of studies on specific CRTC1/3::MAML2 fusion genes in MEC, newly proposed subtypes have emerged, including Warthin-like and non-sebaceous lymphadenoma-like MECs. In addition to the recently defined mucoacinar variant with a serous cell phenotype, MEC devoid of squamous differentiation has also been reported, implying the need to reconsider this basic concept. In this article, we outline the general clinical features and MAML2 status of conventional MEC and review the cytoarchitectural subtypes, with an emphasis on a pitfall in the interpretation of this histologically diverse single entity.

MAML2 gene rearrangement occurs in all Warthin-like mucoepidermoid carcinoma: A reappraisal in a series of 29 cases

Background

Warthin-like Mucoepidermoid carcinoma (MEC) is a new and rare morphological variant of MEC, with only a few case reports in the literature. The clinicopathological, molecular features and bio-behaviors of Warthin-like MEC has not been studied extensively. We reappraisal all Warthin-like MEC patients diagnosed and treated at our hospital.

Methods

Patient characteristics including clinicopathological features, genetic aberrations, treatment, and prognostic information were assessed and evaluated.

Results

Twenty-nine Warthin-like MEC patients were identified, 19 patients were female (65.5 %), and 10 were male (34.5 %). The patients' age varied widely from 8 to 68 years (mean 42.3 years). Genetic aberrations of MAML2 rearrangement were detected in all Warthin-like MEC patients, which suggesting this genetic event is the unique feature of Warthin-like MEC. Twenty-five patients (86.2 %) were assessed as having a low-stage disease (I/II), and four (13.8 %) as having high-clinical stage disease (III/IV). More than half of the patients (16/29) underwent only partial sialoadenectomy; 2 patients underwent extended sialoadenectomy, and 11 patients underwent extended sialoadenectomy with cervical lymph node dissection. After a median follow-up time of 73 months (5-128 months), Twenty-eight patients were alive without recurrence at the end of the follow-up period, one patient died 1 year after surgery due to lung metastasis.

Conclusion

Our data suggested that most Warthin-like MEC exhibited mild clinicopathological course and less aggressive bio-behavior, and an aggressive bio-behavior seemed to be very rare. In addition, in the salivary gland, MAML2 rearrangement seems to be a unique molecular feature of salivary Warthin-like MEC.

Histologic grading of salivary gland mucoepidermoid carcinoma: A comparison of four grading systems and correlation with survival

BACKGROUND

Mucoepidermoid carcinoma (MEC) is the most common malignant lesion of salivary glands. A number of histologic grading systems are in use for MEC with variable agreement between them.

METHODS

This study was aimed at comparison of four grading systems for MEC: two qualitative (modified Healy and MSKCC grading) and two quantitative (AFIP and Brandwein grading). A retrospective search for diagnosed cases of MEC over eight years yielded 11 cases with adequate clinical details and histologic slides available for review. All cases were reviewed and graded as per the four grading systems. An inter-system agreement was assessed, and Kaplan-Meier analysis was performed to correlate the grading with clinical outcomes.

RESULTS

A general agreement between all four grading systems was seen in 72.7% of cases. Brandwein grading assigned the highest percentage of high grades (18.2%), whereas Memorial Sloan-Kettering Cancer Center (MSKCC) assigned the highest percentage of low-grade MEC (72.7%). The agreement between MSKCC and modified Healy was highest at 90% of cases. There was generally a poor agreement between MSKCC and Brandwein grading systems. The MSKCC grading system showed a significant correlation with disease-free survival in MEC patients.

CONCLUSION

Hence, the MSKCC grading system might serve as a better histologic grading system with a predictive value for the biologic behavior of the tumor. Further larger studies are required to validate these findings and implement the uniform use of MSKCC grading for MEC of salivary glands.

Updated Salivary Gland Immunohistochemistry: A Review

CONTEXT.—

Salivary gland neoplasms are rare lesions in the head and neck (H&N) pathology realm. There are more than 20 malignant and 15 benign salivary gland neoplasms in the 5th edition of the World Health Organization classification of H&N tumors. These neoplasms consist of heterogeneous groups of uncommon diseases that make diagnosis and treatment challenging for the clinical team. Using an algorithmic immunohistochemical approach-defined tumor origin and type has proven to be effective and advantageous. Immunohistochemistry may be used as sort of a "diagnostic looking glass," not as a positive or negative type tool, but as an indispensable complement to a hematoxylin-eosin morphologic pattern-based approach. Furthermore, the understanding of the novel discoveries of the salivary gland gene fusions and the molecular aspects of these tumors makes the process easier and improve the diagnosis as well as treatment aspects. This review reflects our experience with more recent diagnostic antibodies, which include MYB RNA, Pan-TRK, PLAG1, LEF1, and NR4A3. Each of these is linked with a specific type of neoplasm; for example, gene fusions involving the PLAG1 and HMGA2 oncogenes are specific for benign pleomorphic adenomas, and MYB is associated with adenoid cystic carcinoma.

OBJECTIVE.—

To review these more recent antibodies, which highly enhance salivary gland neoplasm diagnosis.

DATA SOURCES.—

The study sources involved literature PubMed searches, including multiple review articles, case reports, selected book chapters, and Geisinger Medical Center cases.

CONCLUSIONS.—

Salivary gland tumors are a rare, varied group of lesions in H&N pathology. We need to have continuous readings and revisions of the molecular consequences of these fusion oncoproteins and their subsequent targets, which will eventually lead to the identification of novel driver genes in salivary gland neoplasms.

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%.

Genetic and Immunohistochemical Profiling of Mammary Hidradenoma and Comparison to Mucoepidermoid Carcinoma

Mucoepidermoid carcinoma (MEC) is exceedingly rare in the breast, with <45 cases reported in the literature. Although estrogen receptor/progesterone receptor/human epidermal growth factor 2 triple-negative, MEC is characterized as a special subtype of breast carcinoma with significantly better prognosis than conventional basal-type tumors. Cutaneous hidradenoma (HA) is considered a benign adnexal neoplasm showing histomorphologic overlap with MEC. Rare cases of HA have also been reported in the breast, but these are relatively uncharacterized. In this study, we examined the clinicopathologic, immunohistochemical (IHC), and genetic features of 8 breast HAs, in comparison to 3 mammary MECs. All cases were positive for MAML2 break-apart fluorescence in situ hybridization. Eight cases demonstrated a CRTC1::MAML2 fusion, and one MEC harbored a CRTC3::MAML2 fusion; the latter is a novel finding in the breast. Mutational burden was very low, with only one HA exhibiting a MAP3K1 pathogenic alteration. By IHC, both MEC and HA demonstrated cell type-dependent expression of high- and low-molecular-weight keratins and p63, as well as negative to low-positive estrogen receptor and androgen receptor. Smooth muscle myosin and calponin highlighted an in situ component in the 3 cases of MEC; expression of these myoepithelial markers was negative in HAs. Additional distinguishing characteristics included the growth pattern and tumor architecture, the presence of glandular/luminal cells in HA, and overall higher IHC expression of SOX10, S100 protein, MUC4, and mammaglobin in MEC. Morphologic findings were also compared to a series of 27 cutaneous nonmammary HAs. Mucinous and glandular/luminal cells were identified in significantly more mammary HAs than nonmammary lesions. The findings provide insight into the pathogenesis of MAML2-rearranged neoplasms of the breast, underscore the overlapping genetic features of MEC and HA, and highlight similarities to their extramammary counterparts.

Cervical Gastric-type Adenosquamous Carcinoma: Case Report of a Rare Neoplasm Associated With a BRCA1 Pathogenic Variant

Gastric-type adenocarcinoma is the commonest human papillomavirus (HPV)-independent adenocarcinoma of the cervix. We report a rare case of a primary cervical gastric-type adenocarcinoma with malignant squamous elements (gastric-type adenosquamous carcinoma) in a 64-yr-old female. This is only the third report of a cervical gastric-type adenosquamous carcinoma. The tumor was p16 negative and molecular studies for HPV were negative. Next-generation sequencing showed pathogenic variants in BRCA1 and KRAS , as well as variants of unknown significance in CDK12 and ATM and homozygous deletion of CDKN2A/CDKN2B . Pathologists should be aware that not all cervical adenosquamous carcinomas are HPV-associated and the term gastric-type adenosquamous carcinoma is recommended when malignant squamous elements are present within a gastric-type adenocarcinoma. In reporting this case, we discuss the differential and the possible therapeutic options raised by the presence of pathogenic variants in BRCA1 .

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.

Warthin-like mucoepidermoid carcinoma of the parotid gland: Clinicopathological observation and literature review

Warthin tumor (WT)-like mucoepidermoid carcinoma resembles the histologic pattern of WT and pathologists unaware of this possibility may misdiagnose it as WT with squamous and mucous epithelium metaplasia or WT malignant transfer into mucoepidermoid carcinoma. The present study reported a case of a 41-year-old Chinese female with a solitary mass in the left parotid gland. In this case, microscopic observation revealed prominent lymph node stroma and multiple cystic structures similar to those seen in WT. However, it lacked the two layers of oncocytic epithelial tissue characteristic of WT. Furthermore, fluorescence in situ hybridization detected MAML2 rearrangement in the case. Considering the histological findings, this case was diagnosed as WT-like mucoepidermoid carcinoma. The present case report provides pathological and clinical features to differentiate it from WT malignant transition into mucoepidermoid carcinoma, WT with squamous and mucous epithelium metaplasia and non-sebaceous lymphadenoma-like mucoepidermoid carcinoma. In conclusion, WT-like mucoepidermoid carcinoma as a special subtype of mucoepidermoid carcinoma has special histological characteristics, which required further observations and more case reports to clearly define this variant.

Clinicopathological practice in the differential diagnosis of mucoepidermoid carcinoma from neoplasms with mucinous component

Background

The differential diagnosis of mucoepidermoid carcinoma (MEC) from neoplasm undergoing mucinous features brings more pitfalls to pathologists. Combining specific MAML2 gene rearrangement and histological characteristics may be the solution.

Methods

Twenty-five tumors with mucinous components were selected for differential diagnosis of MEC. All the cases were detected for MAML2 gene rearrangement. The cases diagnosed as MEC were classified into four variants: classic, oncocytic, Warthin-like, and nonclassified, and they were graded using the Brandwein system. The histological characteristics of non-MECs were summarized for differential diagnosis. Univariate survival analysis was performed on MECs.

Results

There were 16 MECs; 62.5% were MAML2 rearranged. For the low-, intermediate-, and high-grade MECs, the rate of rearrangement was 83.3%, 100%, and 28.6%, respectively. Both the oncocytic and Warthin-like MECs were MAML2 rearranged. For the classic and nonclassified MECs without MAML2 rearrangement, non-keratinized squamoid cells and distinctive mucinous cells were essential diagnostic criteria. On survival analysis, all the disease progression occurred in high-grade MECs (p = 0.038). Nine cases were diagnosed as non-MECs: pleomorphic adenoma with mucinous metaplasia showed no ex-capsular involvement; metaplastic Warthin tumor appeared with overt keratinization and residual oncocytic bilayered epithelium; mix squamous cell and glandular papilloma showed an endobronchial papillary growing pattern; adenosquamous carcinoma was accompanied by squamous carcinoma in situ of the overlying mucosa. All the non-MECs were negative for MAML2 rearrangement.

Conclusion

The application of combining MAML2 rearrangement and histological characteristics is helpful in the differential diagnosis between MEC and other tumors with mucinous components.

MAML2-Rearranged Primary Central Mucoepidermoid Carcinoma of the Mandible as an Incidental Finding: A Case Report and Review of the Literature of Molecularly Confirmed Cases

This report presents an extremely rare case of MAML2-rearranged primary central mucoepidermoid carcinoma (MEC) of the mandible that was discovered as an incidental finding. Our review of the literature identified 36 cases of MAML2-rearranged intraosseous lesions of the jaw (30 central MECs, 5 odontogenic cysts with mucous prosoplasia, and 1 glandular odontogenic cyst). Given the therapeutic indications for a diagnosis of MEC (a malignant neoplasm), MAML2 rearrangement should be confirmed in suspected cases of central MEC.

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.

Tight junction gene expression in salivary gland tumors

Salivary gland neoplasms comprise a heterogeneous group of lesions with multiple histological subtypes, each with distinct growth patterns, resulting in a spectrum of tumor-specific prognoses; pleomorphic adenoma (PA) and mucoepidermoid carcinoma (MEC) are the most common representatives of these neoplasms. Many studies have associated specific profiles of membrane and adhesion molecules in salivary gland tissues; these profiles appear to be relevant in tumor biology as well as be interpreted as fingerprints for tumor classification, diagnostic prognostic and therapeutic targets. One of these membrane molecule complexes are the tight junctions, composed by various proteins, in which claudins are protagonists. The aim of this study was to evaluate the expressions of genes that encode tight junction proteins (CLDN-1, -3, -4, -5, -7, and -11, occludin [OCLN], zonula occludens [TJP1, TJP2, and TJP3] and junctional adhesion molecule A [F11R]) in MEC and PA using real time RT-PCR. We observed high expression of CLDN-1 and -7 and low expression of CLDN-3, -11 and TJP2 in MEC compared to PA. PA samples demonstrated high OCLN expression when compared to MEC. CRTC1::MAML2 fusion was detected in 12 of 20 (60.0%) MEC samples and was associated with CLDN7 expression, while the absence of fusion was associated with high histological grade. Increased CLDN5 expression was associated with submandibular gland tumors. This study demonstrated differential expressions of genes encoding tight junction constituent proteins and their associations with tumor characteristics, suggesting their potential future role as diagnostic and prognostic markers.

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.

Development of head and neck pathology in Europe

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

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.