Molecular assessment of allelic loss in Warthin tumors

Pathogenesis of Warthin's Tumor: Neoplastic or Non-Neoplastic?

Warthin's tumor is the second most frequent neoplasm next to pleomorphic adenoma in the salivary gland, mostly in the parotid gland. The epithelial cells constituting a tumor are characterized by the presence of mitochondria that undergo structural and functional changes, resulting in the development of oncocytes. In addition to containing epithelial cells, Warthin's tumors contain abundant lymphocytes with lymph follicles (germinal centers) that are surrounded by epithelial cells. The pathogenesis of Warthin's tumor is not fully understood, and several hypotheses have been proposed. The risk factors for the development of Warthin's tumor, which predominantly occurs in males, include aging, smoking, and radiation exposure. Recently, it has been reported that chronic inflammation and aging cells promote the growth of Warthin's tumor. Several reports regarding the origin of the tumor have suggested that (1) Warthin's tumor is an IgG4-related disease, (2) epithelial cells that compose Warthin's tumor accumulate mitochondria, and (3) Warthin's tumor is a metaplastic lesion in the lymph nodes. It is possible that the pathogenesis of Warthin's tumor includes mitochondrial metabolic abnormalities, accumulation of aged cells, chronic inflammation, and senescence-associated secretory phenotype (SASP). In this short review, we propose that DNA damage, metabolic dysfunction of mitochondria, senescent cells, SASP, human papillomavirus, and IgG4 may be involved in the development of Warthin's tumor.

Expression of FOXI1 and POU2F3 varies among different salivary gland neoplasms and is higher in Warthin tumor

PURPOSE

Salivary gland tumors are histologically diverse. Ionocytes and tuft cells, rare epithelial cells found in normal salivary glands, might be associated with salivary tumors. Here, we explored the expression of FOXI1 and POU2F3, master regulators of ionocytes and tuft cells, respectively, for common salivary neoplasms using immunohistochemistry.

METHODS

We analyzed normal salivary tissues and nine salivary gland tumors; Warthin tumors (WT), pleomorphic adenomas (PA), basal cell adenomas, and oncocytomas were benign, whereas mucoepidermoid, adenoid cystic, acinic cell, salivary duct carcinomas, and polymorphous adenocarcinomas were malignant.

RESULTS

Normal salivary glands contained a few FOXI1- and POU2F3-positive cells in the ducts instead of the acini, consistent with ionocytes and tuft cells, respectively. Among the benign tumors, only WTs and PAs consistently expressed FOXI1 (10/10 and 9/10, respectively). The median H-score of WTs was significantly higher than that of PAs (17.5 vs. 4, P = 0.01). While WTs and PAs harbored POU2F3-positive cells (10/10 and 9/10, respectively), the median H-score was higher in WTs than in PAs (10.5 vs 4, respectively). Furthermore, WTs exhibited a unique staining pattern of FOXI1- and POU2F3-positive cells, which were present in luminal and abluminal locations, respectively. Whereas none of the malignant tumors expressed FOXI1, only adenoid cystic carcinoma consistently expressed POU2F3 (5/5), with a median H-score of 4.

CONCLUSION

The expression patterns of the characteristic transcription factors found in ionocytes and tuft cells vary among salivary gland tumor types and are higher in WT, which might be relevant for understanding and diagnosing salivary gland neoplasms.

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.

KRAS codon 12 mutations characterize a subset of de novo proliferating "metaplastic" Warthin tumors

Warthin tumor (WT; synonym: cystadenolymphoma) represents one of the most frequent salivary gland tumors with a frequency equaling or even outnumbering that of pleomorphic adenomas in some series. Histologically, the tumor displays tall columnar oncocytic cells, arranged into two cell-thick layers lining variably cystic glands within an organoid lymphoid stroma. Tumors with exuberant squamous metaplasia in response to FNA-induced or other types of tissue injury/infarction have been referred to as "metaplastic WTs." However, the same terminology was used for tumors with variable mucinous cell and solid or stratified epidermoid proliferations (occasionally mimicking mucoepidermoid carcinoma), although the "metaplasia concept" has never been proven for the latter. We herein investigated 22 WTs showing prominent mucoepidermoid-like or solid oncocytoma-like proliferations without prior FNA or histological evidence of infarction/ trauma using the TruSight Tumor 15 gene panel and KRAS pyrosequencing. As a control, we tested 11 conventional WTs. No statistically significant differences were observed between the two subcohorts regarding patient's age and tumor size. Six of 22 (27%) proliferating/ metaplastic WTs revealed oncogenic KRAS mutations clustering at codon 12 (exon 2), while all conventional tumors lacked these mutations. Our findings are in line with a neoplastic nature of the epidermoid/ mucoepidermoid proliferations in non-injured "metaplastic" Warthin tumors. We propose the descriptive term "de novo proliferating Warthin tumor" for this variant to distinguish it from infarcted/inflamed genuine metaplastic Warthin tumor.

Histopathologic and clinical outcomes of Milan System categories "non-diagnostic" and "non-neoplastic" of salivary gland fine needle aspirations

INTRODUCTION

The Milan System for Reporting Salivary Gland Cytopathology (MSRSGC) specifies six categories with estimated risks of malignancy (ROM) and suggested management. The estimated ROM is 25% for Non-Diagnostic (ND) category, and 10% for Non-Neoplastic (NN). This study aimed to investigate histopathologic and clinical outcomes of MSRSGC categories ND and NN at the authors' institution.

MATERIALS AND METHODS

Cytopathology fine needle aspiration reports from 2008-2020 were searched for the word "salivary", "parotid", and "submandibular". Cases fitting Non-Diagnostic (ND) and Non-Neoplastic (NN) categories were identified. Follow-up cyto-/histopathologic and clinical data were extracted.

RESULTS

There were 43 ND and 46 NN cases. The average age was 58.3 years. Neoplastic lesions were found in 13 of 43 (30%) ND and 3 of 46 (6.5%) NN. The rate of malignancy in ND category was 14.0% (6/43) and 0% (0/46) in NN category. Four cases in ND (9.3%) and 6 (13.0%) in NN had no neoplasm and instead had an underlying reactive condition (e.g., chronic sialadenitis) or inflammatory lesion (e.g., lymphoepithelial cyst) on histologic follow-up. There was no follow-up pathology in 46.5% NDs (20/43) and 82.6% NNs (38/46); however, no lesions were apparent clinically with a mean follow-up of 3 years and 1.5 years, respectively.

CONCLUSIONS

MSRSGC categories ND and NN are helpful for reporting salivary gland FNA results. With proper clinical and radiologic correlation, ROM of NN is low; however, ROM of ND remains significant. Repeat FNA after correlation for ND cases seems prudent as neoplasms and malignancies may have gone undetected.

Gut-associated lymphoid tissue or so-called “dome” carcinoma of the colon: Review

AIM

To present a comprehensive review of the etiology, clinical features, macroscopic and pathological findings, and clinical significance of Gut-associated lymphoid tissue or “dome” carcinoma of the colon.

METHODS

The English language medical literature on gut- or gastrointestinal-associated lymphoid tissue (GALT) or “dome” carcinoma of the colon was searched and appraised.

RESULTS

GALT/dome-type carcinomas of the colon are thought to arise from the M-cells of the lymphoglandular complex of the intestine. They are typically asymptomatic and have a characteristic endoscopic plaque- or “dome”-like appearance. Although the histology of GALT/dome-type carcinomas displays some variability, they are characterized by submucosal localization, a prominent lymphoid infiltrate with germinal center formation, tumor-infiltrating lymphocytes, absence of desmoplasia, and dilated glands lined by columnar epithelial cells with bland nuclear features and cytoplasmic eosinophilia. None of the patients reported in the literature with follow-up have developed metastatic disease or local recurrence.

CONCLUSION

Increased awareness amongst histopathologists of this variant of colorectal adenocarcinoma is likely to lead to the recognition of more cases.

Increased incidence of Warthin tumours of the parotid gland: a 42-year evaluation

AIM

To evaluate the frequency of Warthin tumours among parotid neoplasms over the past 42 years in a population in rural Germany and to identify potential risk factors.

METHODS

We conducted a retrospective case note evaluation from all patients who underwent parotid surgery between 1975 and 2017. The 42-year time period was evenly split into four quartiles.

RESULTS

A Warthin tumour was diagnosed in 265 out of 806 patients (32.9%). The frequency of Warthin tumour increased steadily from 20.6% in the first decade between 1975 and 1986 to 44.9% in the fourth decade between 2008 and 2017. The age of the patients decreased from 68 years in the first to 62 years in the fourth decade. The male-to-female ratio in Warthin tumour was reduced from 1:5.3 in the first to 1:2.1 in the fourth decade.

CONCLUSION

A Warthin tumour was the most common histological tumour type in the period from 1997 to 2017. We also found a high incidence of multiple tumours, a growing incidence in women and a decreasing age of patients. We propose a re-evaluation of the existing view of the epidemiology of benign parotid tumours, which proposes that pleomorphic adenoma is the most common benign parotid tumour.

Warthin tumor within the superficial lobe of the parotid gland: a suggested criterion for diagnosis

The location of Warthin tumor (WT) in the parotid gland impacts the surgical approach and may be indicative of the elusive origin of this intriguing entity. Location in the deep versus superficial lobe of the gland is not directly addressed when defining WT characteristics. Our observation, of rare occurrence of deep lobe WT, if at all, led to the current investigation. The study design is cohort study. This is a retrospective chart review of all patients undergoing parotidectomy for WT in two tertiary academic referral centers: the Sheba Medical Center (SMC), Israel, and the Christiana Care (CC), Newark, Delaware, USA. 122 consecutive adult patients underwent parotidectomy for WT (72 from SMC and 50 from CC). Seventy percent were males, with a mean age of 60.6 years. Bilateral WT or multi-centric WT were found in 9.8 and 17.2% of the cases, respectively. In one case, the tumor was described as originating in the deep lobe. In all other cases, the tumor originated and was limited to the superficial lobe. 99.2% of WT originated in the superficial lobe, corresponding with the few reports directly addressing its location in the gland. The reason for the tumor to be limited almost uniformly to the superficial lobe is unknown, and could be related to the etiopathogenesis of this elusive entity. We suggest adding tumor location within the superficial lobe to the common characteristics of WT (male, smoking, and lower pole) that serve as "common criterion" while evaluating a parotid lesion.

Nodular Lymphocyte-Predominant Hodgkin Lymphoma in a Warthin Tumor of the Parotid Gland: A Case Report and Literature Review

Hodgkin lymphoma (HL) associated with Warthin tumor (WT) is extremely rare, accounting for only 3 cases of classical HLs. Here, we report for the first time the occurrence of a nodular lymphocyte-predominant Hodgkin lymphoma (NLPHL) involving the lymphoid stroma of a WT of the parotid gland. Pathogenesis of WT is controversial, with both a nodal and a parenchymal possible origin. On the other hand, extranodal involvement by HLs is uncommon. In our case, the coexistence of a WT and of a NLPHL within its stroma and in cervical lymph node emphasizes the importance of a careful evaluation of the lymphoid tissue in WT in order to exclude the possibility of an associated lymphoid malignancy.

Warthin's tumour: Aetiopathogenesis dilemma, ten years of our experience

Despite the volume of studies written after the initial report by Hildebrand (1895) on Warthin's tumour (WT), its aetiopathogenesis continues to be an unresolved and controversial question. Many different genetic and/or environmental aetiological factors seem to act on heterotopic ductal inclusions and may give rise to WT following an unknown tumorigenic event. Recent studies discussed the importance of immunological reactions during the formation of the tumour. A hypersensitive/allergic reaction may play a role in epithelial proliferation and may stimulate the reactivity of the germinal centres in the lymphoid stroma as showed at histological examination. The aim of this study was to inform readers of the current understanding of possible risk factors with a suggested aetiological role in Warthin's tumorigenesis. From 2001 to 2011, a total of 342 patients with benign salivary neoplasm were admitted in the Department of Maxillofacial Surgery of the University of Naples "Federico II". A histological diagnosis of WT was made in 115 of the patients (33.6%); these were retrospectively investigated in our study. Correlation between the onset of WT and positivity for autoimmune diseases and smoking habits was calculated. The incidence rate of autoimmune thyroiditis in our series (9.5%) was significantly greater than that of the general population (0.58%) (p < 0.001). Analysis of our series and review of the literature support the hypothesis that this tumour is the result of an autoimmune reaction. Further studies and larger series are required to confirm this hypothesis and investigate the role of other aetiological factors in WT genesis.

Unilateral Warthin's tumour in a patient of Afro-Caribbean descent

Warthin's tumours are the second most common benign tumours of the parotid gland. The authors report the case of a 40-year-old man of Afro-Caribbean decent who presented with a painless mass at the angle of the right mandible. It was an incidental finding while shaving and was not associated with any symptoms. Arrangements were made for him to undergo an ear, nose and throat (ENT) evaluation. Axial contrast-enhanced CT of head and neck region revealed a well-defined cystic lesion. Fine-needle aspiration cytology was inconclusive. Right superficial partial parotidectomy was performed to remove the lesion. Histological examination confirmed a diagnosis of a Warthin's tumour.

Adenolymphoma: A probing entity: Case report and review

Warthin's tumor undoubtedly is the most frequent monomorphic adenoma of the major salivary glands. Clinically, it appears as a slow-growing tumor often fluctuant on palpation due to its cystic nature. The treatment of choice is complete excision with wide tumor-free margins. This article highlights a case of Warthin's tumor of the parotid gland in an elderly male patient along with a review of the literature on the aforementioned pathology.

Nonsebaceous lymphadenoma in the parotid gland: true neoplastic or reactive? A report of two cases

We report 2 rare cases of nonsebaceous lymphadenoma (NSL) in the parotid gland. In both cases, microscopic examination revealed central dilated duct-like structure and its surrounding many cysts in the background of the lymphoid stroma. The cysts were lined with luminal cells and abluminal cells, with the latter being predominant. Occasionally, foci of abluminal epithelial islands were observed. Immunohistochemical findings showed that these tumors had basal cell phenotypes and could support the diagnosis of NSL. The microscopic architectural pattern indicated a cystic dilated duct-glands unit and metaplasia or hyperplasia of abluminal cells. We wondered whether these NSLs were true neoplasia or an indication of a nonneoplastic reactive process. Further investigation of molecular studies of large series in, for example, the clonal or chromosomal state, would be necessary to clarify this point.

Human α-defensin (DEFA) gene expression helps to characterise benign and malignant salivary gland tumours

BACKGROUND

Because of the infrequence of salivary gland tumours and their complex histopathological diagnosis it is still difficult to exactly predict their clinical course by means of recurrence, malignant progression and metastasis. In order to define new proliferation associated genes, purpose of this study was to investigate the expression of human α-defensins (DEFA) 1/3 and 4 in different tumour entities of the salivary glands with respect to malignancy.

METHODS

Tissue of salivary glands (n=10), pleomorphic adenomas (n=10), cystadenolymphomas (n=10), adenocarcinomas (n=10), adenoidcystic carcinomas (n=10), and mucoepidermoid carcinomas (n=10) was obtained during routine surgical procedures. RNA was extracted according to standard protocols. Transcript levels of DEFA 1/3 and 4 were analyzed by quantitative realtime PCR and compared with healthy salivary gland tissue. Additionally, the proteins encoded by DEFA 1/3 and DEFA 4 were visualized in paraffin-embedded tissue sections by immunohistochemical staining.

RESULTS

Human α-defensins are traceable in healthy as well as in pathological altered salivary gland tissue. In comparison with healthy tissue, the gene expression of DEFA 1/3 and 4 was significantly (p<0.05) increased in all tumours - except for a significant decrease of DEFA 4 gene expression in pleomorphic adenomas and a similar transcript level for DEFA 1/3 compared to healthy salivary glands.

CONCLUSIONS

A decreased gene expression of DEFA 1/3 and 4 might protect pleomorphic adenomas from malignant transformation into adenocarcinomas. A similar expression pattern of DEFA-1/3 and -4 in cystadenolymphomas and inflamed salivary glands underlines a potential importance of immunological reactions during the formation of Warthin's tumour.

MAML2 rearrangement in Warthin's tumour: a fluorescent in situ hybridisation study of metaplastic variants

BACKGROUND

Warthin's tumour (WT) is a common benign lesion of the major salivary glands. The nature of WT remains controversial, with particular regard to the presence of clonal chromosomal abnormalities, including the t(11;19) translocation involving the CRTC1 and MAML2 genes, that have been identified in both WT and mucoepidermoid carcinoma. In this study, we focused our attention on metaplastic WT variants, and we conducted a fluorescent in situ hybridisation (FISH) analysis for the presence of MAML2 gene rearrangement.

METHODS

Dual-colour FISH analysis was performed on paraffin-embedded sections of eight WTs showing metaplastic changes (five with squamous metaplasia, two with mucinous metaplasia and one with both) using a MAML2 break-apart probe.

RESULTS

Presence of split signals indicative of gene rearrangement was identified in a subset of cells in areas of squamous metaplasia in two samples of WT. No rearrangement was observed in the oncocytic epithelium, in lymphocytes and in areas of mucinous metaplasia.

CONCLUSIONS

The presence of a small subpopulation of cells carrying MAML2 rearrangement in areas of squamous metaplasia within WT could predispose these lesions to malignant transformation in mucoepidermoid carcinoma and could represent a molecular link between the two entities.

Tumor de Warthin da glândula parótida: estudo de 70 casos

OBJETIVO: Relatar as características clínicas, tratamento e complicações.dos tumores de Warthin. MÉTODOS: Estudo retrospectivo com 70 pacientes submetidos à ressecção de cistoadenoma papilífero linfomatoso,. Variáveis analisadas: idade, sexo, etnia, presença ou não de tabagismo, sítio primário do tumor, tamanho do tumor em centímetros, presença de bilateralidade, tipo de operação, multicentricidade, complicações do tratamento, presença de recidiva no seguimento e tempo de seguimento.. RESULTADOS: Quarenta e quatro pacientes (62,8%) eram do sexo masculino e 26 (37,2%), do sexo feminino, com média etária de 56,7 anos, O tabagismo estava presente em 55 (78,6%) pacientes, (94,3%) dos tumores eram unilaterais e quatro (5,7%) bilaterais, com tamanho médio de 4,1cm ao exame físico. As complicações foram 14 (19%) casos de paresia e/ou paralisia facial, seroma em 10 (13,8%), síndrome de Frey em três (4%), hematoma em dois (2,7%) e infecção de ferida operatória em um (1,5%) caso. CONCLUSÃO: O tumor de Warthin tem maior incidência no sexo masculino, em tabagistas e localização unilateral predominante na glândula parótida. A parotidectomia superficial com preservação do nervo facial mostrou-se eficaz em 100% casos. As complicações encontradas foram paresias ou paralisias transitórias, seroma, síndrome de Frey, hematoma e infecção de ferida operatória.

Immunohistochemical localization of mdm-2, p27Kip1 and bcl-2 in Warthin's tumor of the parotid gland

Background

Warthin's tumor is a benign monomorphic adenoma with unclear origin that almost occur exclusively in the parotid gland. Etiology of Warthin's tumor as well as its malignant potential are still unclear. Therefore immunohistochemical assessment of Warthin's tumor may be useful to detect its origin or its malignant transformation potential.

Aims and objectives

The present study aims to investigate the immunohistochemical expression of murine double minute-2 (mdm-2), p27^Kip1 and B cell lymphoma-2 (bcl-2) in Warthin's tumor of parotid gland and also to clarify the role of these proteins in the behavior of that tumor.

Methods

Twenty paraffin blocks of cases previously diagnosed as Warthin's tumor were collected for immunohistochemical staining with primary antibodies against mdm-2, p27^Kip1 and bcl-2 using streptavidin-biotin immunoperoxidase staining system.

Results

All cases showed immunopositivity for mdm-2 and p27^Kip1 while 18/20 showed bcl-2 immunopositivity. Both layers of the neoplastic epithelial cells that line the cystic spaces showed immunopositivity with all antibodies used. Goblet cells were mdm-2 immunonegative while myoepithelial cells were p27^Kip-1 immunonegative. Areas of epithelial proliferation that formed buds were p27^Kip-1 and bcl-2 immunopositive.

Conclusion

Mdm-2 played a tumor-suppressor role that might be implicated with the benign behavior of Warthin's tumor. The mutual expression of both p27^Kip1 and bcl-2 suggested a protective role of these slowly proliferating cells from apoptosis to maintain their survival and elevated bcl-2 expression offers a significant protection against p27^Kip1-mediated apoptosis.

CRTC1/MAML2 fusion transcript in Warthin's tumor and mucoepidermoid carcinoma: evidence for a common genetic association

Translocations and gene fusions have an important early role in tumorigenesis. The t(11;19) translocation and its CRTC1/MAML2 fusion transcript have been identified in several examples of both Warthin's tumor and mucoepidermoid carcinoma and are believed to be associated with the development of a subset of these tumors. To determine whether Warthin's tumor and mucoepidermoid carcinoma are genetically related, we used reverse transcriptase-polymerase chain reaction and DNA sequencing to analyze microdissected components of three tumors consisting of Warthin's tumor and mucoepidermoid carcinoma. We also investigated a metastatic melanoma to Warthin's tumor and a Warthin's carcinoma of the parotid gland for comparison. The fusion transcript was identified in both Warthin's tumor and matching mucoepidermoid carcinoma components of all three tumors, in the Warthin's carcinoma, and in the Warthin's tumor component but not in the metastatic melanoma. The results provide evidence for a link between the t(11;19) fusion gene and the development of a subset of Warthin's tumors with concurrent mucoepidermoid carcinoma and possible malignant transformation to Warthin's carcinoma. This article contains Supplementary Material available at http://www.interscience.wiley.com/jpages/1045-2257/suppmat.

Multifocal multi-site Warthin tumour

The unique case of a 55-year-old man with multifocal adenolymphoma (Warthin's tumour) of both parotid glands, the neck and post-nasal space is presented. Warthin tumour is almost exclusively a parotid tumour but is known to be bilateral in 7-10% of cases and multifocal in 2% of cases. Most extraglandular Warthin tumours have been located in neck lymph nodes and only a few cases have been reported from other sites. The presented case is unique in having synchronous and metachronous Warthin tumours, as well as one of the tumours being neither truly parotid, nor within a lymph node.

Tumor Suppressor Gene Alterations in Respiratory Epithelial Adenomatoid Hamartoma (REAH)

Respiratory epithelial adenomatoid hamartoma (REAH) is an unusual benign sinonasal glandular proliferation. REAH is not considered a neoplasm, although, no molecular evidence exists to support or refute this possibility. Microdissection of 10 cases of REAH, 9 cases of sinonasal adenocarcinoma (SNAC) and 10 cases of chronic sinusitis was performed. DNA was extracted and polymerase chain reaction performed using fluorescently labeled primers flanking known tumor suppressor genes on chromosomes 9p (CDKN2/p16), 11p (H-ras), 17p (p53), and 18q (DCC/DPC4). Polymerase chain reaction products were analyzed semiquantitatively by capillary electrophoresis. Allele ratios were calculated using the peak height from the shorter allele divided by the peak height from the longer allele. The loss of heterozygosity (LOH) ratio was calculated as the allele ratio from tumor tissue divided by the allele ratio from normal tissue. The fractional allelic loss (FAL) was calculated as the percentage of loci that harbored LOH divided by the number of loci that were informative. REAH demonstrated an intermediate FAL of 31% compared with SNAC (64%) and chronic sinusitis (2%). REAH and SNAC had the highest LOH for multiple loci located on 9p (p16) and 18q (DCC/DPC4). The molecular profile of REAH shows a mean FAL of 31%, which would be considered unusually high for a non-neoplastic entity. Appreciable allelic loss within REAH suggests the possibility that REAH may be a benign neoplasm rather than a hamartoma.

Warthin Tumors Do Not Have Microsatellite Instability and Express Normal DNA Mismatch Repair Proteins

Context.—Warthin tumors are controversial entities with a poorly understood etiology. Although some investigators have suggested a neoplastic origin, others have supported a developmental anomaly. A recent study described the absence of staining for hMLH1 and hMSH2 proteins in the epithelial component of Warthin tumors, suggesting that they arise secondary to defects in the DNA mismatch repair system.

Objective.—To determine if Warthin tumors exhibit evidence of DNA mismatch repair defects.

Design.—Immunostains for hMLH1 and hMSH2 were performed using a standard approach. Microdissection of the epithelial component was followed by DNA extraction from the tissue fragments. Polymerase chain reaction and capillary electrophoresis analyses were performed for the following 5 National Cancer Institute–recommended microsatellites: D2s123, D5s346, D17s250, BAT25, and BAT26.

Patients.—Twelve patients with Warthin tumors were included.

Results.—The immunostains for hMLH1 and hMSH2 showed preserved expression in the nuclei of the epithelial component of all Warthin tumors. No microsatellite instability was detected, and no loss of heterozygosity was seen.

Conclusions.—These results are not concordant with previously reported results showing loss of expression of the hMLH1 and hMSH2 DNA mismatch repair enzymes in the epithelial component of Warthin tumors. Furthermore, no microsatellite instability was detected in the 5 loci tested for each tumor in this series. These data demonstrate that Warthin tumors do not have evidence of DNA mismatch repair defects at the genomic or protein expression level.