Obligate basal cell component in salivary oncocytoma facilitates distinction from acinic cell carcinoma

Oncocytic Lesions of Salivary Glands: Morphological, Immunohistochemical, and Molecular Findings

The fifth edition of the World Health Organization (WHO) classification introduces new diagnostic methods based on genetic alterations, providing insight into the molecular basis of lesions. As a result, the classification system has evolved, new entities have been introduced, and existing entities have been reclassified. Oncocytic lesions of salivary glands are a group of neoplastic conditions characterized by the presence of oncocytic cells. These lesions present a diagnostic challenge due to their overlapping histological features. Therefore, a comprehensive evaluation, including morphological, immunohistochemical, and molecular analysis, is crucial for accurate diagnosis and appropriate management. Accurate classification of salivary gland pathologies is essential for selecting the appropriate treatment methods and predicting outcomes. The introduction of new therapeutic approaches, such as targeted therapies for malignant salivary gland tumors, has improved patient outcomes. However, to effectively implement these therapies in clinical practice, a clear classification of lesions is necessary.

Top Ten Differentials to Mull Over for Head and Neck Myoepithelial Neoplasms

BACKGROUND

Myoepithelial neoplasms of the salivary gland are benign or malignant neoplasms composed exclusively of neoplastic myoepithelial cells. These tumors, including the benign myoepithelioma and the malignant counterpart myoepithelial carcinoma, exhibit a wide range of cytomorphologic features and architectural patterns.

METHODS

Review.

RESULTS

Myoepithelial cells can be epithelial, plasmacytoid, clear cell, spindle cell, and/or oncocytic cell, arranging as trabeculae, solid sheets, nests, cords, and/or single cells. A stromal component is commonly but not universally present, Therefore, their differential diagnoses are quite broad, including salivary gland neoplasms especially those with a myoepithelial component, plasmacytoma, melanoma, and various mesenchymal tumors.

CONCLUSION

In this review, we summarize the characteristic histologic features, useful immunohistochemical panel, and common molecular alterations of myoepithelial tumors and their top differential diagnoses. A logical stepwise algorithmic approach and an immunohistochemical panel to include multiple myoepithelial markers are essential to establish the correct diagnosis.

Mucoepidermoid carcinoma may be devoid of squamoid cells by immunohistochemistry: expanding the histologic and immunohistochemical spectrum of MAML2- rearranged salivary gland tumours

Mucoepidermoid carcinoma (MEC) is historically defined by a mix of squamoid, intermediate, and mucous cells, but we have recently encountered several cases lacking immunoreactivity for squamous markers p40, p63, and CK5/6 despite MAML2 fusions. This study will characterise these unique tumours. Ten MEC were collected arising from the parotid gland (n = 4), submandibular gland (n = 2), nasopharynx (n = 1), base of tongue (n = 1), bronchus (n = 1), and trachea (n = 1). Six tumours were low-grade, two intermediate-grade, one high-grade, and one demonstrated low-grade areas with high-grade transformation. Four cases were oncocytic, four had clear-cell features, two had spindle cell features, and one high-grade MEC had prominent solid, cord-like, and micropapillary features. The tumours were negative for p40 (10/10), p63 (10/10), and CK5/6 (9/9). Targeted RNA sequencing demonstrated CRTC1::MAML2 in five cases, CRTC3::MAML2 in two, and a novel MAML2::CEP126 in the unusual high-grade case. In two cases with insufficient RNA, MAML2 fluorescence in situ hybridisation (FISH) showed rearrangement. Genetically-confirmed MEC may lack overt squamous differentiation by histology and immunohistochemistry. While most cases harboured canonical fusions and fit within the spectra of MEC variants with oncocytic, clear cell, and/or spindle cell features, one had a novel MAML2::CEP126 fusion and unusual morphology. In MEC without squamoid cells, the use of immunohistochemistry may hinder, rather than aid, the correct diagnosis. In such cases, MAML2 analysis is most useful. The historical definition of MEC as a carcinoma with squamoid, intermediate and mucous cells should be revisited.

Comparison of Diagnostic Reliability of p63 and Smooth Muscle Actin in Salivary Gland Neoplasms

Salivary gland neoplasms pose considerable diagnostic difficulty owing to their diverse histological features in individual lesions and the presence of a number of types and variants & similar histological features with other tumor entities. Myoepithelial and basal cells play a significant role in the pathogenesis of salivary gland neoplasm. p63 and smooth muscle actin are more reliable markers for identifying these cells and not studied much comparing their reliability in the diagnosis of salivary gland neoplasms. Hence, the aim of this study is to evaluate and compare the diagnostic reliability of immunohistochemical markers such as p63 and smooth muscle actin (SMA) in the diagnosis of various benign and malignant salivary gland neoplasms. The study comprises of 18 samples categorized into two groups: Group I comprised 9 cases, of which 4 cases were Pleomorphic adenoma, 2 cases were Myoepithelioma, 2 cases of Basal cell adenoma and 1 case was Warthin's tumor; and Group II consisted of 9cases, of which 3 was Mucoepidermoid carcinoma, 1 cases were Myoepithelial carcinoma and 5 cases were Adenoid cystic carcinoma. The selected cases were subjected to immunohistochemistry (IHC) procedure to assess the expression pattern of p63 and smooth muscle actin. The obtained data was analysed statistically by using Mann-Whitney test. In SMA, strong positivity for epithelial and connective tissue components of benign salivary neoplasm is about 22.2%respectively. In malignant salivary neoplasm, SMA was strongly positive for the epithelial and connective tissue component of about 77.7% and 88.8% cases respectively. The difference in the connective tissue components was found to be statistically significant (U = 24, P = 0.032). P63 was strongly positive for the epithelial and connective tissue component of benign salivary neoplasm of about 33.3% and 11.1% cases respectively.In malignant salivary neoplasm, p63 was strongly positive for the epithelial component of about 66.6% cases and connective tissue is completely negative. Alpha-SMA can be utilized as reliable IHC markers for salivary gland neoplasms due to its diagnostic importance in tumors with myoepithelial origin indicative of the histogenesis of salivary gland tumors and even p63 can be used as specific markers for differentiation of malignant salivary gland tumors.

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.

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.

Analysis of the Clinical Relevance of Histological Classification of Benign Epithelial Salivary Gland Tumours

INTRODUCTION

A vast increase in knowledge of numerous aspects of malignant salivary gland tumours has emerged during the last decade and, for several reasons, this has not been the case in benign epithelial salivary gland tumours. We have performed a literature review to investigate whether an accurate histological diagnosis of the 11 different types of benign epithelial salivary gland tumours is correlated to any differences in their clinical behaviour.

METHODS

A search was performed for histological classifications, recurrence rates and risks for malignant transformation, treatment modalities, and prognosis of these tumours. The search was performed primarily through PubMed, Google Scholar, and all versions of WHO classifications since 1972, as well as numerous textbooks on salivary gland tumours/head and neck/pathology/oncology. A large number of archival salivary tumours were also reviewed histologically.

RESULTS

Pleomorphic adenomas carry a considerable risk (5-15%) for malignant transformation but, albeit to a much lesser degree, so do basal cell adenomas and Warthin tumours, while the other eight types virtually never develop into malignancy. Pleomorphic adenoma has a rather high risk for recurrence while recurrence occurs only occasionally in sialadenoma papilliferum, oncocytoma, canalicular adenoma, myoepithelioma and the membranous type of basal cell adenoma. Papillomas, lymphadenoma, sebaceous adenoma, cystadenoma, basal cell adenoma (solid, trabecular and tubular subtypes) very rarely, if ever, recur.

CONCLUSIONS

A correct histopathological diagnosis of these tumours is necessary due to (1) preventing confusion with malignant salivary gland tumours; (2) only one (pleomorphic adenoma) has a considerable risk for malignant transformation, but all four histological types of basal cell adenoma can occasionally develop into malignancy, as does Warthin tumour; (3) sialadenoma papilliferum, oncocytoma, canalicular adenoma, myoepithelioma and Warthin tumour only occasionally recur; while (4) intraductal and inverted papilloma, lymphadenoma, sebaceous adenoma, cystadenoma, basal cell adenoma (apart from the membranous type) virtually never recur. No biomarker was found to be relevant for predicting recurrence or potential malignant development. Guidelines for appropriate treatment strategies are given.

Oncocytic Carcinoma of the Submandibular Gland: A Case Report

Oncocytic carcinoma (OC) of the submandibular gland is extremely rare. A 76-year-old man complained of a painless tumor of the right neck. Ultrasonography demonstrated swelling in the lymph nodes of the neck, and fine-needle aspiration cytology of a node showed metastatic carcinoma with oncocytic features. Radical surgery revealed infiltrating carcinoma of the right submandibular gland with lymph node metastases (19/23). Tumor cells showed less atypia and had abundant eosinophilic cytoplasm, which stained deep blue with phosphotungstic acid-hematoxylin stain. The cells were immunohistochemically positive for cytokeratin 7 but negative for p63 and SOX10. We diagnosed the tumor as OC. Chemoradiotherapy was performed after surgery. The patient showed no sign of recurrence until 42 months after the operation, when lymph node swelling was detected in the mediastinum by computed tomography scanning. With no further treatment, the patient is alive with lymph node swellings in the mediastinum and pulmonary hilum 80 months after surgery.

Salivary acinic cell carcinoma: reappraisal and update

Epidemiologic and clinicopathologic features, therapeutic strategies, and prognosis for acinic cell carcinoma of the major and minor salivary glands are critically reviewed. We explore histopathologic, histochemical, electron microscopic and immunohistochemical aspects and discuss histologic grading, histogenesis, animal models, and genetic events. In the context of possible diagnostic difficulties, the relationship to mammary analog secretory carcinoma is probed and a classification is suggested. Areas of controversy or uncertainty, which may benefit from further investigations, are also highlighted.

DOG1, p63, and S100 protein: a novel immunohistochemical panel in the differential diagnosis of oncocytic salivary gland neoplasms in fine-needle aspiration cell blocks

INTRODUCTION

DOG1 is a calcium-activated chloride channel protein that may have a potential role in secretory cells of salivary glands and tumors derived from them. Its role in cytologic specimens is not well documented. This study was performed to evaluate its utility in separating acinic cell carcinoma (AciCC) from other closely related differential diagnoses on cytologic samples. In addition, an immunohistochemical panel consisting of DOG1, p63, and S100 protein to assist in the subclassification of these salivary gland neoplasms with oncocytic differentiation was also investigated.

MATERIALS AND METHODS

Thirty-one fine-needle aspiration cell blocks (CBs) of oncocytic salivary gland neoplasms (16 Warthin tumors [WTs], 10 AciCCs, 3 mucoepidermoid carcinomas [MECs], and 2 oncocytomas [ONCs]), and 75 salivary gland resections (7 WTs, 27 AciCCs, 36 MECs, 2 high-grade adenocarcinomas, 2 ONCs, 1 papillary cystadenoma) were immunostained for DOG1, p63, and S100.

RESULTS

DOG1 and p63 were very useful in distinguishing AciCC from WT on CB, because 100% of WTs were DOG1-negative and 87.5% were p63-positive, whereas 70% of AciCCs were DOG1-positive and 100% were p63-negative. The resection results correlated with those on CBs: 100% of WTs were DOG1-negative and 86% were p63-positive, whereas 93% of AciCCs were DOG1-positive and 89% were p63-negative. S100 and DOG1 were negative in both WTs and ONCs, with <10% S100 positivity in AciCCs.

CONCLUSIONS

DOG1 was very helpful in separating AciCC from WT, MEC, and ONC. In summary, an immunohistochemical panel including DOG1, p63, and S100 can significantly improve the accuracy of diagnosing oncocytic salivary gland neoplasms on CBs.

P63 expression can be used in differential diagnosis of salivary gland acinic cell and mucoepidermoid carcinomas

Differentiation of salivary gland acinic cell carcinoma from mucoepidermoid carcinoma can be diagnostically challenging as both may have prominent mucin production. P63 is a p53 homologue required for limb and epidermal morphogenesis. It is expressed in basal and myoepithelial cells of normal salivary gland tissues. In this immunohistochemical study, we examined the expression of p63 in salivary gland acinic cell and mucoepidermoid carcinomas (MEC) and its use in differentiating these two entities. A search was performed and appropriate cases were selected from Lifespan Hospital System archives as well as the consult archives of one author (DRG). 31 salivary gland acinic cell carcinomas (ACC) and 24 MEC were examined for p63 expression by immunohistochemistry. The nuclear immunoreactivity was examined by both authors and was graded semi-quantitatively with negative being less than 10 % of cells staining. Positive staining was graded as follows: 10-25 % of tumor cells staining was weakly positive, 26-75 % of tumor cells staining was moderately positive, and 76-100 % of tumor cells staining was strongly positive. Negative nuclear staining of the tumor cells was seen in 30/31 (96 %) of salivary gland ACC while 1/31 (3 %) showed diffuse nuclear staining of the tumor cells. This latter case was later reclassified as mammary analogue secretory carcinoma following confirmatory molecular testing for the ETV6-NTRK3 fusion gene. Strong positive nuclear staining of the tumor cells was seen in 24 (100 %) of salivary gland MEC cases. P63 is an immunohistochemical stain that can potentially aid in differentiating unusual ACC with prominent mucin production from MEC of the salivary gland. According to this study, acinic cell carcinoma is always negative for p63 immunoreactivity while mucoepidermoid carcinoma is always positive.