Central mucoepidermoid carcinoma, a case report with molecular analysis of the TORC1/MAML2 gene fusion

Fusions in salivary gland neoplasms: a review of practical diagnostic applications

There is an ongoing explosion of new information regarding the underlying molecular alterations driving a variety of salivary gland neoplasms. The volume of this emerging data makes it difficult to keep up with and may cause pathologists to believe that salivary gland neoplasms cannot be diagnosed without genetic analysis. This review focuses on the practical diagnostic applications of molecular tools in surgical pathology specimens.

Diagnostic Reliability of CRTC1/3::MAML2 Gene Fusion Transcripts in Discriminating Histologically Similar Intraosseous Mucoepidermoid Carcinoma from Glandular Odontogenic Cyst: A Systematic Review and Meta-analysis

BACKGROUND

Intraosseous mucoepidermoid carcinoma (IMEC) and Glandular odontogenic cyst (GOC) are those two pathological entities causing diagnostic dilemma due to the histopathological similarity. An accurate distinction between the two entities is difficult as both presents with a common radiological and histological similarities. The aim of our systematic review was to establish the diagnostic reliability of CRTC1/3::MAML2 gene fusion for the distinction between IMEC and GOC.

METHODS

A complete electronic literature search was made in MEDLINE by PubMed, Google Scholar, and EMBASE databases. Articles with keywords using molecular genetic findings of CRTC1/3::MAML2 gene fusion transcripts, IMEC and GOC were assessed and included for the systematic review.

RESULTS

Twelve subgroups having both qualitative and quantitative analysis revealed CRTC1/3::MAML2 sensitivity of 100% and specificity of 70.59% in differentiating GOC and IMEC. Fixed-effects model confirmed translocation-negative cases to have a decreased risk of association with IMEC (combined odds ratio 8.770, 95% confidence interval - 2.45 to 31.45, p < 0.002).

CONCLUSIONS

The current evidence supports that in all cases with positive gene fusion transcript of the CRTC1/3::MAML2 was specific for IMEC and was significantly differentiating it from GOC. Whereas cases of IMEC with negative gene fusion transcript pose diagnostic difficulty in differentiating from a GOC which is negative for CRTC1/3::MAML2 expression.

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.

Conjunctival Adenosquamous Carcinoma Lacks MAML2 Translocation: A Variant of Squamous Cell Carcinoma With Mucoepidermoid Differentiation and Aggressive Behavior?

Conjunctival adenosquamous carcinoma, also known as mucoepidermoid carcinoma (MEC), is a rare tumor that preferentially affects the perilimbal area of the conjunctiva with aggressive local invasion. Consisting of infiltrative proliferation of squamous cells and mucous cells, its morphologic features are reminiscent of the salivary gland-type MEC except for the absence of intermediate cells and frequent keratin production. We reported 2 cases of conjunctival adenosquamous carcinoma and, for the first time, studied the MAML2 translocation status of this rare entity. The 2 patients were women, aged 45 and 42 years, presenting with an erythematous lesion in the left lower palpebral conjunctiva and a pigmented nodule over the left nasal conjunctiva, respectively. One tumor recurred 6 months after the initial biopsy. Excision with lid reconstruction and postoperative radiotherapy was performed for margin involvement and perineural invasion. This patient was disease free at 3-year follow-up. The other patient was lost to follow-up after tumor excision. Fluorescence in situ hybridization and reverse transcription polymerase chain reaction failed to demonstrate MAML2 translocation and CRCT1-MAML2 transcripts in both tumors. The absence of this characteristic translocation and reappraisal of the cellular composition, morphologic features, and precursor lesion suggest that conjunctival MEC may represent a variant of conjunctival squamous cell carcinoma but not related to the salivary gland-type MEC.

Mucoepidermoid Carcinoma in the Skull of an Orange-winged Amazon Parrot (Amazona amazonica)

A 33-year-old female intact orange-winged Amazon parrot (Amazona amazonica) presented for a slowly growing mass over the right eye. A computed tomography scan performed with and without intravenous contrast revealed a heterogeneous mixed soft tissue and mineral-dense mass with a small area of non-contrast-enhancing fluid density located between the orbits at the caudal aspect of the nasal passages, with associated lysis of the right caudal nasal passage and the right frontal bone. Following euthanasia, the mass was found to consist of soft tissue between the right eye and nostril over the right frontal bone. Lysis of the underlying bone resulted in a bony defect leading into the infraorbital sinus along the dorsorostral aspect of the right eye. Histopathology revealed an unencapsulated, poorly demarcated, highly cellular neoplasm composed of islands and trabeculae of neoplastic cells embedded in abundant loose fibrovascular stroma which completely obliterated the cortical bone and sinuses of the rostral skull and infiltrated the surrounding muscle and soft tissue. Histologically, the tumor was consistent with a high-grade mucoepidermoid carcinoma, characterized by the presence of epidermoid, intermediate, and mucous-producing cell types. No evidence of metastasis was identified. The tissue of origin was suspected to be salivary or nasal mucous glands, but was difficult to confirm due to distortion of normal tissue architecture as a result of the tumor. Although mucoepidermoid carcinomas are a common salivary gland tumor in human medicine, they are not well recognized in avian species, and no specific case reports exist describing this pathology in an Amazon parrot. Despite the lack of distinct salivary glands in most avian species, mucoepidermoid carcinomas can occur, can cause significant clinical disease, and should be included as a differential diagnosis for avian patients presenting with similar lesions.

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.

The reliability of MAML2 gene rearrangement in discriminating between histologically similar glandular odontogenic cysts and intraosseous mucoepidermoid carcinomas

OBJECTIVE

MAML2 expression is proven in the majority of mucoepidermoid carcinomas (MECs) arising in salivary glands. MEC can also occur intraosseously (IMEC). Glandular odontogenic cyst (GOC) is an odontogenic cyst with histologic overlap with IMEC. This study aimed to determine the reliability of MAML2 in distinguishing IMEC cases from GOC cases.

STUDY DESIGN

An institutional review board-approved retrospective search of IMEC, GOC, and IMEC with prior history of GOC was performed within the archives of the University of Florida and the University of Alberta Oral Pathology Biopsy Services. Nine cases from 5 patients were selected. Break-apart fluorescent in situ hybridization analysis was performed on 7 cases for the presence of MAML2 rearrangement.

RESULTS

Four cases had negative MAML2 gene rearrangement, and 3 cases had positive MAML2 gene rearrangement.

CONCLUSIONS

Although it can be concluded that the 3 cases with positive translocation for MAML2 were IMECs, the same conclusion could not be drawn for the 4 cases with negative translocation. Whether the cases that were negative for translocation were GOCs with MEC-like islands or were MAML2-negative IMECs could not be ascertained. Therefore, MAML2 rearrangement is not always reliable in differentiating IMECs from GOCs with overlapping histology.

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.

Intraosseous mucoepidermoid carcinoma: Outcome review

OBJECTIVE

Identify the effect of patient characteristics, disease traits, and treatment modality on patient outcomes in the rare disease process of intraosseous mucoepidermoid carcinoma.

STUDY DESIGN

Retrospective review of institutional case records and literature.

METHODS

This study includes one case report, a literature review of the MEDLINE database from 1950 through June 2017 using keywords "intraosseous" and "mucoepidermoid," and a query of the University of California, Los Angeles, Department of Pathology database for all documented cases of intraosseous mucoepidermoid carcinoma of the head and neck.

RESULTS

Indicators of poorer prognosis were male gender (P = 0.0071) and higher histological grade (P = 0.0095). Lesion site, size, association with odontogenic cyst, and treatment type did not have a statistically significant correlation with patient outcomes. There also was no statistically significant correlation observed between treatment modality and recurrent or progressive disease when stratified by histological grade of the cancer.

CONCLUSION

This study identified male gender and high histological tumor grade as poor prognostic indicators; however, it did not reveal a statistically significant relationship between treatment modality and patient outcomes. Data regarding patient outcomes following treatment was limited due to loss to follow-up, suggesting that further investigation is required. Based on this review, decisions regarding treatment should be clinically guided and individually tailored to the patient's baseline health, disease severity, and the patient's treatment goals. A multi-disciplinary conference, as was utilized in the presented case report, may be the best approach to treatment planning for these patients at this time.

LEVEL OF EVIDENCE

4. Laryngoscope, 128:1083-1092, 2018.

New Developments in Salivary Gland Pathology: Clinically Useful Ancillary Testing and New Potentially Targetable Molecular Alterations

Accurate diagnosis of salivary gland tumors can be challenging because of the many diagnostic entities, the sometimes extensive morphologic overlap, and the rarity of most tumor types. Ancillary testing is beginning to ameliorate some of these challenges through access to newer immunohistochemical stains and fluorescence in situ hybridization probes, which can limit differential diagnostic considerations in some cases. These ancillary testing strategies are especially useful in small biopsy samples, including aspiration cytology. Molecular techniques are also expanding our understanding of salivary gland tumor pathology and are helping to identify potential targets that may improve treatment for some of these tumors. Here, we summarize the clinical use of new immunohistochemical markers in our practice and review the current understanding of chromosomal rearrangements in salivary gland tumor pathology, emphasizing the prospects for exploiting molecular alterations in salivary gland tumors for diagnosis and targeted therapy. We find that immunohistochemistry and fluorescence in situ hybridization are powerful tools toward the diagnosis of salivary gland tumors, especially when used in a systematic manner based on morphologic differential-diagnostic considerations. As new targeted therapies emerge, it will become increasingly vital to incorporate appropriate molecular testing into the pathologic evaluation of salivary gland cancers.

A case of central mucoepidermoid carcinoma associated with dentigerous cyst

Mucoepidermoid carcinoma (MEC) is the most common malignant salivary gland neoplasm. Central MEC (CMEC) is a rare primary intraosseous bony lesion with an incidence of 2%–4.3% of all MECs reported. In this article, we present a rare case of a CMEC in the anterior region of maxilla at a 43-year-old female patient that was arising from a dentigerous cyst. CMECs are extremely rare tumor. They are usually low-grade lesions with favorable prognosis. Odontogenic cysts are one of the origins of this lesion. Treatment of impacted tooth is necessary in the early stage for prevention of this neoplasm.

Intraosseous mucoepidermoid carcinoma: report of two cases

Intraosseous mucoepidermoid carcinoma is a rare tumor which affects women more than men and is more common in the mandible. The radiological examination reveals a well-defined unilocular or multilocular radiolucent lesion. This tumor may resemble a glandular odontogenic cyst, particularly in incisional biopsies. The accurate diagnosis of these lesions is imperative because the subsequent treatment of each lesion would be different. The purpose of this study is to report two cases of intraosseous mucoepidermoid carcinoma and explicate the differentiating criteria of this lesion from the glandular odontogenic cyst.

Glandular odontogenic cysts (GOCs) lack MAML2 rearrangements: a finding to discredit the putative nature of GOC as a precursor to central mucoepidermoid carcinoma

Glandular odontogenic cyst (GOC) is a cyst of the gnathic bones that is characterized by squamous and glandular differentiation. The histopathologic features of GOC overlap considerably with central mucoepidermoid carcinoma (MEC), suggesting that GOC could be a precursor lesion to, or even a low-grade form of, central MEC. Differentiating the two lesions may be difficult or impossible on a limited biopsy. MAML2 rearrangements have been recently found to be specific for MEC, even those arising in the jaws. An analysis of MAML2 in GOCs could help clarify its relationship with central MEC. Tissue blocks from 21 GOCs and 5 central MECs were retrieved from the surgical pathology archives of The Johns Hopkins Hospital. Each MEC exhibited solid areas and clear-cut stromal invasion. In addition, 4 of the MECs demonstrated cystic areas that were histologically similar to GOC. Break-apart fluorescence in situ hybridization for MAML2 was performed. For the MECs, analysis was performed on both the solid components and the cystic areas that resembled GOC. MAML2 rearrangements were identified in all 5 of the MECs, but in none of the 21 GOCs (100 vs. 0 %; p < 0.0001, Fisher's Exact). In the MECs, the rearrangement was present in both the solid and GOC-like cystic areas. While central MECs consistently harbor the MAML2 rearrangement, even in low-grade cystic areas that resemble a pre-existing GOC, true GOCs do not. Accordingly, GOC does not appear to represent an early or low-grade form of central MEC, but rather an unrelated lesion. The high sensitivity and specificity of MAML2 rearrangement for MECs points to its utility as a diagnostic adjunct in separating mucinous cystic lesions of the gnathic bones.

Predominantly cystic central mucoepidermoid carcinoma developing from a previously diagnosed dentigerous cyst: case report and review of the literature

Primary intraosseous mucoepidermoid carcinoma of the jawbones is an extremely rare malignant salivary gland tumour constituting 2-4.3% of all the reported mucoepidermoid carcinomas. We report a case of intraosseous mucoepidermoid carcinoma of the mandible in an 80-year old female patient developing from a previously diagnosed dentigerous cyst. An excisional biopsy was performed and the histopathological features confirmed low grade-cystic intraosseous mucoepidermoid carcinoma. The origin of central mucoepidermoid carcinoma could be suggested to be from the epithelial lining of previously diagnosed dentigerous cyst. Thus, emphasizing the need for careful examination of the entire excision specimen to rule out such neoplastic transformation of epithelial lining of odontogenic cyst and provide appropriate and effective treatment.

Intraosseous carcinoma of the jaws--a clinicopathologic review. Part I: Metastatic and salivary-type carcinomas

This is the first part of a 3-part comprehensive review of intraosseous carcinoma of the jaws. We have outlined 4 groups of intraosseous carcinoma of the jaws (metastatic, salivary-type, odontogenic, and primary intraosseous carcinoma), emphasizing the need for accurate diagnosis and the problems associated with changing classification systems, standardization of diagnostic criteria and nomenclature, and the accuracy of existing literature. In this first part, the features of metastatic and the very rare salivary-type carcinomas of the jaws are examined with particular emphasis on histologic and immunohistochemical characteristics, diagnostic difficulties, and uncertainties.

Clear cell carcinoma and clear cell odontogenic carcinoma: a comparative clinicopathologic and immunohistochemical study

Clear cell carcinoma or hyalinizing clear cell carcinoma (CCC) and clear cell odontogenic carcinoma (CCOC) are rare, low-grade and typically indolent malignancies that can be diagnostically challenging. In this study the clinicopathologic, histologic, and immunohistochemical features of 17 CCCs and 12 CCOCs are examined. The differential diagnosis of clear cell malignancies in the head and neck is discussed. The relationship of CCCs and CCOCs to other clear cell tumors on the basis of their immunohistochemical staining patterns is postulated.