Oncocytic mucoepidermoid carcinoma of the salivary glands

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.

Top Ten Oncocytic Head and Neck Lesions to Contemplate

BACKGROUND

Oncocytes are a component of many metaplastic and neoplastic lesions throughout the head and neck area, primarily originating in salivary/seromucinous glands and the thyroid gland. In addition, other lesions can contain cells that mimic oncocytes (pseudo-oncocytes); these can be of epithelial or non-epithelial origin.

METHODS

Review article.

RESULTS

Oncocytic metaplasia is common in seromucinous glands throughout the upper aerodigestive tract, most notable in the oral cavity, nasopharynx and larynx. The main oncocytic salivary gland neoplasms are Warthin tumor and oncocytoma. Infarction of Warthin tumor may lead to recognition difficulties. Oncocytic subtypes of mucoepidermoid carcinoma and intraductal carcinoma have morphologic and immunohistochemical features that allow distinction from major oncocytic entities. Oncocytic thyroid tumors include adenoma, carcinoma (follicular, papillary and medullary), along with poorly differentiated tumors. Oncocytic papillary sinonasal and middle ear tumors must be distinguished from low grade adenocarcinomas. Pseudo-oncocytic entities include paraganglioma, Langerhans cell histiocytosis, giant cell tumor, rhabdomyoma, and metastatic tumors.

CONCLUSIONS

Correct diagnosis of oncocytic head and neck lesions requires a knowledge of the spectrum of possible entities, their characteristic sites of occurrence, architecture, histomorphology, and immunohistochemistry. Oncocytic subtypes of several newly described entities are now recognized. Both epithelial and non-epithelial mimics of oncocytes exist. The molecular features of oncocytic tumors can be helpful in their diagnosis and understanding their pathogenesis.

Intraoral oncocytic mucoepidermoid carcinoma - A rare case report and review of the literature

Rationale:

Oncocytic mucoepidermoid carcinoma (OMEC) is a rare variant of mucoepidermoid carcinoma (MEC). The parotid gland is the most common site of OMEC, whereas intraoral OMEC is infrequent.

Patient Concerns:

A 55-year-old male presented with an asymptomatic mass at the palate for 20 years.

Diagnosis:

Incisional biopsy showed classic MEC.

Treatment:

The patient underwent partial maxillectomy under general anaesthesia. The excised specimen revealed sheets of oncocytes additional to the tumour cells found in the incisional biopsy. Additional special stain and immunohistochemical stain confirmed the diagnosis of OMEC.

Outcomes:

The patient was followed up for 3 years with no recurrence.

Take-away Lessons:

The diagnosis of OMEC needs to be differentiated from other salivary gland tumours containing oncocytes. Moreover, the conventional grading system applied to OMEC may not correlate with their behavior and may need further review.

Cytopathology approach to rare salivary gland lesions with oncocytic features

Salivary glands located in the head and neck area are known to have different lesions with prominent oncocytic features. Fine needle aspiration is usually the initial approach in the management of these lesions, whether they represent neoplastic or non-neoplastic processes. Owing to the limited material present upon cytopathologic examination, knowledge of variants and subtypes of various oncocytic lesions that can occur in this area is of major importance to provide the most accurate interpretation to the patients and clinicians. In this article, we selected rare lesions of the salivary glands that may exhibit oncocytic changes, and provided a brief discussion of each one of them, with emphasis on challenges in navigating the differential diagnosis that these cases may pose, from the cytopathology standpoint.

Updates in Salivary Gland Fine Needle Aspiration Biopsy: The Use of the Milan System and Ancillary Testing

Salivary gland fine needle aspiration biopsies remain common specimens seen by most cytology services. The diagnostic diversity and overlap between many of the lesions seen with these biopsies impart many challenges for the cytopathologist, rendering most specific diagnoses impossible with cytology alone. Here, the use of the Milan System for the classification of salivary gland fine needle aspiration biopsy FNAB is discussed, together with the potential use of ancillary testing in arriving at definitive diagnoses.

Oncocytes in Mucoepidermoid Carcinoma of the Palate: Diagnostic Challenges

The origin of a salivary gland tumour is attributed to cells at various levels of differentiation which present histologically as diverse tissues and cellular patterns. Mitochondria-rich, eosinophilic oncocytes are cells commonly encountered in salivary gland neoplasms. We report a case of mucoepidermoid carcinoma (MEC) in the palate of a 43-year-old female that exhibited a prominent oncocytic component. While the parotid and submandibular glands have been reported as predominant sites for oncocytic MEC (OMEC), the palate and minor salivary glands are rare sites for occurrence. Also, most of the reported cases of OMEC have been histologically of low-grade mucoepidermoid carcinoma with large cystic spaces and good prognosis. In this article, we discuss the differential diagnosis and diagnostic workup of an MEC presenting with oncocytes.

Oncocytic mucoepidermoid carcinoma of the parotid gland: A case report and review of the literature

Oncocytic metaplasia rarely has been reported in mucoepidermoid carcinomas. Most salivary gland lesions with oncocytic change are benign; therefore, it is important to distinguish mucoepidermoid carcinoma from other entities that may show prominent oncocytic change. We report a rare case of oncocytic mucoepidermoid carcinoma in a 65-year-old woman.

A Rare Case of Exclusively Oncocytic Mucoepidermoid Carcinoma with MAML2 Translocation

Mucoepidermoid carcinoma is the most common malignant tumor of the salivary gland. The oncocytic variant of mucoepidermoid carcinoma (OMEC) is rare and a small subset shows exclusive oncocytic morphology. Here we report an OMEC case of the parotid gland in a 74-year-old woman with exclusive oncocytes and rare mucocytes. The oncocytes showed diffuse nuclear positivity with p63 immunostaining. The MAML2 translocation was present, supporting the diagnosis of OMEC. Distinguishing OMEC with exclusive oncocytes from oncocytoma and oncocytic carcinoma can be very challenging for pathologists and is critical for proper clinical management. Our experience suggests that appropriate ancillary studies, especially the MAML2 translocation, may provide the essential evidence in difficult cases. Our literature review shows that the presence of mucocytes in an oncocytic neoplasm might be an important morphologic clue of OMEC.

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 gland FNA cytology: role as a triage tool and an approach to pitfalls in cytomorphology

OBJECTIVE

To highlight the importance of salivary gland fine needle aspiration (FNA) cytology as a triage tool for surgery and to determine its sensitivity and specificity. To discuss the diagnostic pitfalls and potential role of ancillary techniques in diagnosis and prognosis.

METHODS

The study included a total of 920 cases of salivary gland FNAs received in the cytopathology department of University College London Hospital during December 2004 to December 2012. The cases with known histological outcomes were analysed to determine the sensitivity and specificity.

RESULTS

Surgery was carried out on 180 (19.6%) of 920 patients. Excluding nine with inadequate/non-diagnostic cytology, the sensitivity of FNA cytology for a malignant outcome was 89% (33/37) and the specificity was 97% (130/134). Diagnostic pitfalls are discussed with respect to eight FNAs with discrepant histology. Histological outcome was not available for 740 cases (80.4%): excluding 88 non-diagnostic FNAs, 324 (49.7%) had non-neoplastic diagnoses (not indicating surgery) and 328 (50.3%) had neoplastic diagnoses, which included recurrences/metastases of known tumours. Patients with other neoplasms on FNA were lost to follow-up and may have had surgery elsewhere. Cases with clinical concerns were discussed at weekly multidisciplinary meetings.

CONCLUSION

Salivary gland FNA is crucial in the distinction of non-neoplastic from neoplastic lesions, emphasizing the fact that FNA is an excellent triage tool for surgery. Salivary gland FNA has a high sensitivity and specificity. However, it is important to interpret the cytological diagnoses in the light of clinical findings and imaging. Diagnostic pitfalls are seen in a minority of cases and could potentially be overcome with the help of recently described diagnostic and prognostic markers.

The Molecular Pathology of Salivary Gland Tumors with Translocations

Presented here are the salivary gland tumors now recognized to have significant and highly prevalent translocations. These include both common and uncommon malignancies: mucoepidermoid carcinoma, adenoid cystic carcinoma, mammary analog secretory carcinoma, and clear cell carcinoma. These mutations have potential diagnostic applications, particularly in difficult and challenging variant morphologies are unusually challenging differential diagnoses. Practical applications of the molecular pathology of these tumors is discussed. The mutational assessment may also prove to have therapeutic importance, as targeted therapies may be generated for these tumors in the future.

High-grade oncocytic mucoepidermoid carcinoma of the minor salivary gland origin: a case report with immunohistochemical study

An oncocytic mucoepidermoid carcinoma arising from the minor salivary gland origin is extremely rare. We report on a 44-year-old man with a high-grade oncocytic mucoepidermoid carcinoma originating in the minor salivary gland of the posterior mandible. All tumor cells showed the expected pattern of immunoreactivity, with positive results for the antimitochondrial antibody and p63, and negative results for the androgenic receptor antibody. Microscopically, the tumor was considered to be a high-grade carcinoma in the grading systems of the Armed Forces Institute of Pathology and Brandwein. The patient underwent a partial mandibulectomy, and the lesion was reconstructed with a right fibula osteofasciocutaneous flap under general anesthesia. The patient is currently under long-term follow-up.

Oncocytic mucoepidermoid carcinoma: clinicopathologic description in a series of 12 cases

Mucoepidermoid carcinoma (MEC) is the most common salivary gland malignancy. Oncocytic MEC (OMEC) has been rarely reported with previous cases suggesting they are largely cystic low-grade neoplasms with a favorable prognosis. The differential diagnosis of OMEC includes numerous oncocytic/"oncocytoid" neoplasms. Some are benign while others are aggressive. Recent evidence suggests that p63 is a reliable marker in the diagnosis of conventional MEC but has not been explored in OMEC. We searched the archives of various institutions for examples of OMEC to re-appraise the grade, and to evaluate p63 immunohistochemistry as a tool to separate OMEC from its potential mimics. A total of 12 cases were identified. There were 6 males and 6 females with an age range of 30 to 79 years. Most occurred in the parotid (9) with 1 each in the sublingual gland, hard palate and neck. They showed minimal cystic content and were infiltrative and solid tumors spanning all grades. All tumors had focal mucin production and were composed almost exclusively of oncocytic cells with 2 cases demonstrating conventional MEC areas. All 6 cases tested showed the majority of oncocytic cells staining with p63 in a diffuse pattern, demonstrating its utility in the diagnosis of OMEC. Of the 6 cases with follow-up information, 1 case had local recurrence 8 years after the initial surgery. Three cases showed skin or bone invasion. None had lymph node/distant metastases. In summary, OMEC behaves as a low-grade tumor, and is diffusely positive for p63, which may aid in its differential diagnosis.

Advances in salivary gland pathology

This review summarizes the new findings on salivary gland pathology under the following categories: immunohistochemistry; molecular genetics; newly recognized tumour types; known tumour entities with new findings; and progression of salivary gland tumours. In the application of immunohistochemistry, CD117 can aid in highlighting the luminal cell component of various salivary gland tumours, whereas p63 or maspin can aid in highlighting the abluminal cell component. A high Ki67 index remains the most useful marker to predict adverse outcome in salivary gland carcinoma. Specific chromosomal translocations are recognized in pleomorphic adenoma (with translocation involving PLGA1 or HMGA2 gene) and mucoepidermoid carcinoma (with MECT1-MAML2 gene fusion). Newly recognized entities include: sclerosing polycystic adenosis (with recent molecular evidence supporting its neoplastic nature), sclerosing mucoepidermoid carcinoma with eosinophilia, keratocystoma, adenoma with additional stromal component (lymphadenoma, lipoadenoma and adenofibroma), cribriform adenocarcinoma of the tongue and signet ring adenocarcinoma of minor salivary gland. Known tumour entities with new findings include: salivary duct carcinoma (with newly recognized mucinous, micropapillary and sarcomatoid variants), intraductal carcinoma (with controversies in terminology), mucoepidermoid carcinoma (with newly proposed grading parameters and oncocytic variant), epithelial-myoepithelial carcinoma (with newly recognized morphological variants), small cell carcinoma (with most cases being related to Merkel cell carcinoma), extranodal marginal zone B-cell lymphoma (with specific chromosomal translocation) and chronic sclerosing sialadenitis (being a component of IgG4-related sclerosing disease). Progression of salivary gland tumours can take the form of malignant transformation of a benign tumour, progression from low-grade to high-grade carcinoma, dedifferentiation, or stromal invasion of an in situ carcinoma.

Clear cell and eosinophilic oncocytomas of salivary gland: Cytological variants or parallels?

Oncocytomas are uncommon tumors of the salivary gland. They have an abundance of mitochondria, which is manifested as granular eosinophilic cytoplasm by light microscopy. On histological sections, presence of cytoplasmic glycogen and/or fixation artifact can impart cytoplasmic clearing, and oncocytomas with a predominance of clear cytoplasm are labeled clear cell oncocytomas. Two forms of oncocytoma, eosinophilic and clear cell, have been described in the surgical pathology literature. The purpose of this manuscript is to conduct a comparative cytological assessment to ascertain parallels and differences between the two variants.

Oncocytic mucoepidermoid carcinoma of parotid gland origin

This article reports 3 cases of oncocytic mucoepidermoid carcinoma of the parotid gland and compares them with 9 cases from the literature with emphasis on clinical behavior, treatment, and recurrence rate. The tumor occurs most often in the middle-aged to elderly, with a decided predilection for the parotid gland. All three oncocytic mucoepidermoid carcinomas from the Armed Forces Institute of Pathology series were low grade with extensive oncocytic change. Treatment modalities consisted of superficial parotidectomy, total parotidectomy, or total parotidectomy. The mean follow-up interval was 5.5 years. Only one case from the literature, a high-grade mucoepidermoid carcinoma, recurred. Results of this study indicate that the parotid gland oncocytic mucoepidermoid carcinoma behaves in a fashion similar to typical mucoepidermoid carcinoma, with prognosis dependent on clinical stage, histopathologic grade, and adequacy of treatment. Recognizing the spectrum of oncocytic differentiation in salivary gland tumors will serve to establish appropriate diagnoses and treatment.

Mucoepidermoid carcinoma: a clinicopathologic study of 80 patients with special reference to histological grading

We sought to review our experience with salivary mucoepidermoid carcinoma (MEC) over two decades to confirm the validity and reproducibility of histologic grading and to investigate MIB-1 index as a prognosticator. Diagnosis was confirmed on 80 cases, and chart review or patient contact was achieved for 48 patients, with follow-up from 5 to 240 months (median 36 months). Immunohistochemistry with citrate antigen retrieval for MIB-1 was performed on a subset of cases. Kaplan-Meier survival curves were generated for each stage, site, and grade according to our proposed grading system. To address the issue of grading reproducibility, 20 slides were circulated among five observers, without prior discussion; slides were categorized as low-, intermediate-, or high-grade according to one's "own" criteria, and then according to the AFIP criteria proposed by Goode et al.10 Weighted kappa (kappa) estimates were obtained to describe the extent of agreement between pairs of rating. The Wilcoxon signed rank test or the Friedman test as appropriate tested variation across ratings. There was no gender predominance and a wide age range (15-86 years, median 49 years). The two most common sites were parotid and palate. All grade 1 MECs presented as Stage I tumors, and no failures were seen for this category. The local disease failure rates at 75 months for grades 2 and 3 MEC were 30% and 70%, respectively. Tumor grade, stage, and negative margin status all correlated with disease-free survival (DFS) (p = 0.0091, 0.0002, and 0.048, respectively). The MIB index was not found to be predictive of grade. Regarding the reproducibility of grading, the interobserver variation for pathologists using their "own" grading, as expressed by the kappa value, ranged from good agreement (kappa = 0.79) to poor (kappa = 0.27) (average kappa = 0.49). A somewhat better interobserver reproducibility was achieved when the pathologists utilized the standardized AFIP criteria (average kappa = 0.61, range 0.38-0.77). This greater agreement was also reflected in the Friedman test (statistical testing of intraobserver equality), which indicated significant differences in using one's own grading systems (p = 0.0001) but not in applying the AFIP "standardized" grading (p = 0.33). When one's own grading was compared with the AFIP grading, there were 100 pairs of grading "events," with 46 disagreements/100 pairs. For 98% of disagreements, the AFIP grading "downgraded" tumors. This led us to reanalyze a subset of 31 patients for DFS versus grade, for our grading schema compared with the AFIP grading. Although statistical significance was not achieved for this subset, the log rank value revealed a trend for our grading (p = 0.0993) compared with the Goode schema (p = 0.2493). This clinicopathologic analysis confirms the predictive value of tumor staging and three-tiered histologic grading. Our grading exercise confirms that there is significant grading disparity for MEC, even among experienced ENT/oral pathologists. The improved reproducibility obtained when the weighted AFIP criteria were used speaks to the need for an accepted and easily reproducible system. However, these proposed criteria have a tendency to downgrade MEC. Therefore, the addition of other criteria (such as vascular invasion, pattern of tumor infiltration [i.e., small islands and individual cells vs cohesive islands]) is necessary. We propose a modified grading schema, which enhances predictability and provides much needed reproducibility.

Oncocytic mucoepidermoid carcinoma of the parotid gland: report of a case with DNA ploidy analysis and review of the literature

A 44-year-old female presented with a painful mass in the left parotid gland. Histologic examination revealed the characteristic picture of oncocytic mucoepidermoid carcinoma (OMEC) composed mainly of sheets of oncocytic cells with uniform nuclei and eosinophilic cytoplasm, focally smaller epidermoid cells surrounding poorly formed glandular spaces, and a few cystic structures lined by well-differentiated mucous cells with intracytoplasmic mucin. Immunohistochemical staining with antimitochondrial antibody showed granular cytoplasmic positivity in oncocytic cells. The resulting histogram for DNA ploidy analysis was of diploid type. OMEC of the parotid gland is a recently described rare neoplasm. Only six cases have been previously reported in the literature. For an accurate approach in the management of patients, OMEC should be considered in the differential diagnosis of oncocytic lesions of the parotid gland, most of which are benign.