Translocation t(11;19)(q21;p13.1) as the sole chromosome abnormality in a cystadenolymphoma (Warthin's tumor) of the parotid gland

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.

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.

The Milan System classification of Warthin tumor: A large institutional study of 124 cases highlighting cytologic features that limit definitive interpretation

BACKGROUND

Fine-needle aspiration (FNA) is highly accurate for the diagnosis of Warthin tumor (WT). However, there is a minor subset of WT cases that are more challenging to interpret. The goal of this study is to identify factors that limit definitive diagnosis of WT on FNA.

METHODS

All WT surgical specimens diagnosed during a 6.5-year study period were retrospectively identified and the preceding cytologic specimen diagnostic categories were analyzed. Of particular interest were WT cases with indeterminate or malignant interpretations. Cases that noted squamous or mucinous change in either the surgical or cytologic reports were also reviewed.

RESULTS

A total of 157 WT surgical specimens were identified, with 124 (79.0%) having prior FNAs. The distribution of cytologic diagnostic categories was 12 (9.7%) nondiagnostic, 10 (8.1%) nonneoplastic, 13 (10.5%) atypia of undetermined significance (AUS), 82 (66.1%) neoplasm: benign, 4 (3.2%) salivary gland neoplasm of uncertain malignant potential (SUMP), 2 (1.6%) suspicious for malignancy, and 1 (0.8%) malignant. Of the 20 cases in indeterminate/malignant categories, a majority noted either squamoid (9 of 20) or mucinous (2 of 20) changes. The remainder noted scant cellularity as a limiting factor to interpretation. Additionally, 27 cases mentioned squamous or mucinous change in the surgical or cytology report, with a wide spectrum of cytologic categorization including 2 (7.4%) nondiagnostic, 2 (7.4%) nonneoplastic, 7 (25.9%) AUS, 8 (29.6%) neoplasm: benign, 4 (14.8%) SUMP, 2 (7.4%) suspicious for malignancy, and 1 (3.7%) malignant.

CONCLUSIONS

This study identified 2 key causes for indeterminate or misclassification of WT on FNA: specimen hypocellularity and metaplastic changes. Recognition of the potential for squamous and mucinous metaplastic changes combined with observance of some helpful diagnostic clues such as the presence of crystalloids may aid in preventing diagnostic pitfalls.

Warthin-Like Mucoepidermoid Carcinoma: A Morphological Spectrum - A Report of 3 Cases with Histological and Cytological Findings and Review of the Literature

BACKGROUND

Mucoepidermoid carcinoma (MEC) showing Warthin's tumor (WT)-like features is a low-grade malignancy which should be differentiated from WT. Morphological features may be distinctly different in each case, causing diagnostic difficulties.

CASE PRESENTATION

Three cases were presented and discussed with their morphologies. All cases that presented with a mass in the parotid gland went to parotidectomy, and all had preoperative fine-needle aspirations (FNAs). Case 1 was a 16-year-old female; FNA was suggestive of WT and initially interpreted as WT histologically. Case 2 was a 27-year-old male; FNA was interpreted as noninformative due to the presence of cyst fluid only. Case 3 was a 53-year-old male and cytologically was found to be suspicious for MEC which contained squamous and goblet cells on a mucoid background. On histopathological examination, case 2 and case 3 were morphologically consistent with low-grade MEC with WT-like features. Prominent lymphoid stroma and the cystic pattern were the characters of these tumors. Case 1 had the classical WT appearance with some mucinous and squamous metaplasia which could only be interpreted as MEC after the detection of MAML2 rearrangement by FISH. The other 2 showed either focal or relatively diffuse usual low-grade MEC findings, and case 3 was also confirmed by MAML2 rearrangement.

CONCLUSION

Cytological and histopathological features revealed a spectrum. Differentiating WT-like MECs from ordinary WTs may be challenging. On the one end of the spectrum, they may look very much like WT, and on the other end, even though usual MEC features are present, still, WT-like appearance may pose diagnostic difficulty. Showing MAML2 rearrangement in these cases is very helpful. The presence of mucinous and squamous cells in an otherwise WT-like looking tumor should be alarming for MEC, and if possible, each case should be analyzed for MAML2 rearrangement.

MAML2 rearrangement as a useful diagnostic marker discriminating between Warthin tumour and Warthin-like mucoepidermoid carcinoma

Warthin tumour is the second most common benign neoplasm of salivary glands. Despite its relatively characteristic histology, it may sometimes mimic other lesions. Here, we report two female non-smoker patients diagnosed with low-grade mucoepidermoid carcinoma with oncocytic epithelium and prominent lymphoid (Warthin-like) stroma and with molecularly confirmed MAML2 rearrangement. In addition, we screened a consecutive series of 114 Warthin tumour cases by means of MAML2 break apart fluorescence in situ hybridization to assess its value in differential diagnosis. MAML2 rearrangement was detected in both mucoepidermoid carcinoma cases, while all Warthin tumours were negative. Taking into account the literature data, Warthin-like mucoepidermoid carcinomas are more frequently observed in women, while a slight male predominance and smoking history are typical for Warthin tumour. In addition, the patients with Warthin-like mucoepidermoid carcinoma were significantly younger than those with Warthin tumour. To conclude, Warthin-like mucoepidermoid carcinoma may usually be suspected based on histology, while the diagnosis can be confirmed by means of molecular assays such as FISH. The investigation of MAML2 status is particularly advised when Warthin tumour is considered in a young, non-smoking, female patient.

The significance of mucinous metaplasia in Warthin tumor: a frequent occurrence and potential pitfall

Mucinous metaplasia in Warthin tumor (WT) is a recognized phenomenon. Nevertheless, its presence can create a diagnostic challenge in the distinction from the newly proposed variant of mucoepidermoid carcinoma (MEC), Warthin-like MEC. In this study, we evaluated the significance and diagnostic relevance of mucinous metaplasia in WTs. A total of 30 WTs diagnosed based on resection specimens formed the basis of this retrospective study. Mucicarmine staining was performed to identify mucinous metaplasia, and fluorescence in situ hybridization (FISH) analysis was used to detect MAML2 gene rearrangement. After review, one MAML2 rearranged case was reclassified as Warthin-like MEC as the classic bilayered epithelium in WT was not identified. The diagnosis of WT was confirmed in the remaining 29 cases. Mucinous metaplasia was encountered in 24 WTs (83%), with 14% (4/29) having an abundant amount. We found that mucinous metaplasia correlated with tumor size (p < 0.05). Age and sex distribution were similar in WT cases with or without mucinous metaplasia. In addition, neither the presence of squamous metaplasia nor the time interval between fine-needle aspiration and surgery was related to mucinous metaplasia (p > 0.05). The MAML2 FISH analyses performed in 18 WTs with variable amounts of mucinous metaplasia were negative for rearrangement. In conclusion, mucinous metaplasia is fairly common in WTs and shows a significant correlation with tumor size. Therefore, caution should be taken to avoid overinterpretation of WT with mucinous metaplasia as MEC in cases showing the classic bilayered oncocytic lining epithelium.

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.

MAML2 Rearrangements in Variant Forms of Mucoepidermoid Carcinoma: Ancillary Diagnostic Testing for the Ciliated and Warthin-like Variants

Mucoepidermoid carcinoma (MEC) is the most common salivary gland malignancy. Recent studies have shown that most MECs harbor gene fusions involving MAML2-an alteration that appears to be specific for MEC, a finding that could be diagnostically useful. While most cases of MEC are histologically straightforward, uncommon variants can cause considerable diagnostic difficulty. We present 2 variants of MEC for which MAML2 studies were crucial in establishing a diagnosis: a previously undescribed ciliated variant, and the recently described Warthin-like variant. All cases of ciliated and Warthin-like MEC were retrieved from the archives of The Johns Hopkins Hospital. Break-apart fluorescence in situ hybridization for MAML2 was performed on all cases. One ciliated MEC and 6 Warthin-like MECs were identified. The ciliated MEC presented as a 4.6 cm cystic lymph node metastasis originating from the tongue base in a 47-year-old woman. The Warthin-like MECs presented as parotid masses ranging in size from 1.2 to 3.3 (mean, 2.7 cm) in 4 women and 2 men. The ciliated MEC consisted of macrocystic spaces punctuated by tubulopapillary proliferations of squamoid cells and ciliated columnar cells. The Warthin-like MECs were comprised of cystic spaces lined by multilayered oncocytic to squamoid cells surrounded by a circumscribed cuff of lymphoid tissue with germinal centers. In these cases, the Warthin-like areas dominated the histologic picture. Conventional MEC, when present, represented a minor tumor component. MAML2 rearrangements were identified in all cases. Warthin-like MEC, and now a ciliated form of MEC, are newly described variants of a common salivary gland carcinoma. Unfamiliarity with these novel forms, unanticipated cellular features (eg, cilia), and morphologic overlap with mundane benign processes (eg, developmental ciliated cysts, Warthin tumor) or other carcinomas (eg, ciliated human papillomavirus-related carcinoma) may render these variants susceptible to misdiagnosis. These unusual variants appear to consistently harbor MAML2 fusions-a finding that establishes a clear link to conventional MEC and provides a valuable adjunct in establishing the diagnosis.

Thymic Mucoepidermoid Carcinoma

Thymic mucoepidermoid carcinoma (TMEC) is a vanishingly rare entity that usually presents as low to intermediate grade MEC and carries a better prognosis when compared with other poorly differentiated thymic carcinomas. The recently described fusions, t(11;19)(q21;p13) CREB (cAMP response element-binding protein)-regulated transcription coactivator 1 and MAML2, mastermind-like gene 2 (CRTC1-MAML2) and t(11:15)(q21;q26) CRTC3-MAML2 characterize a considerable proportion of MEC examples arising from a variety of anatomical sites. Recent data point out that the aberrant proteins produced by this fusion drive oncogenesis by disrupting the cAMP/CREB and NOTCH1 pathways. To date, only 2 TMEC cases have been reported to have MAML2 rearrangements, a feature that was found to be absent in TMEC mimics. These findings led the authors to recommend this test as a diagnostic tool in the differential diagnosis for thymic carcinoma. Herein, we present a case of TMEC arising in a 58-year-old woman, which was predominantly cystic with intracystic papillary formations composed of a mixture of mucinous cells and intermediate/epidermoid eosinophilic cells. This case was negative for CTCR1-MAML2 and CTCR3-MAML2 fusion transcripts by reverse transcriptase polymerase chain reaction and lacked a MAML2 rearrangement by fluorescence in situ hybridization. We report a CTCR1/3-MAML2 fusion and MAML2 rearrangement–negative TMEC, indicating that a different molecular pathway must be involved in the generation of these tumors. The possibility of fusion-negative TMEC should be taken into consideration in the differential diagnosis of a thymic carcinoma.

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.

11q21 rearrangement is a frequent and highly specific genetic alteration in mucoepidermoid carcinoma

Mucoepidermoid carcinoma (MEC) is the most common malignant salivary gland tumor. Translocation t(11;19)(q21;p13) involving the MECT1 and MAML2 genes has been suggested as a diagnostic marker in these tumors. To determine the specificity of 11q21 locus rearrangements for MEC, fluorescence in situ hybridization analysis with specific MEC-I Dual Color Break Apart Probe was performed on a tissue microarray containing samples from almost 1200 salivary gland adenomas and carcinomas. Rearrangements of 11q21 were observed in 40% of 217 MECs. The frequency of rearrangements decreased with tumor grade and was found in 53% of G1, 43% of G2, and 31% of G3 tumors (P=0.015). There were no 11q21 rearrangements found in other salivary gland carcinomas including 142 adenoid cystic carcinomas, 104 acinic cell adenocarcinomas, 76 adenocarcinoma not otherwise specified, 38 epithelial-myoepithelial carcinomas, 15 polymorphous low-grade adenocarcinomas, 18 basal cell adenocarcinomas, 19 myoepithelial carcinomas, 12 papillary cystadenocarcinomas, 6 salivary duct carcinomas, and 10 oncocytic carcinomas. Furthermore, all analyzed salivary gland adenomas, including 39 cases of Warthin tumor and control samples, either from the salivary gland or from other organs were negative for 11q21 rearrangements. It is concluded that MECT1-MAML2 gene fusion is a highly specific genetic alteration in MEC with predominance in low-grade and intermediate-grade tumors.

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.

Translocations in epithelial cancers

Genomic translocations leading to the expression of chimeric transcripts characterize several hematologic, mesenchymal and epithelial malignancies. While several gene fusions have been linked to essential molecular events in hematologic malignancies, the identification and characterization of recurrent chimeric transcripts in epithelial cancers has been limited. However, the recent discovery of the recurrent gene fusions in prostate cancer has sparked a revitalization of the quest to identify novel rearrangements in epithelial malignancies. Here, the molecular mechanisms of gene fusions that drive several epithelial cancers and the recent technological advances that increase the speed and reliability of recurrent gene fusion discovery are explored.

A link between the expression of the stem cell marker HMGA2, grading, and the fusion CRTC1-MAML2 in mucoepidermoid carcinoma

Recently, the concept of cancer stem cells and their expression of embryonic stem cell markers has gained considerable experimental support. In this study, we examined the expression of one such marker, the high-mobility group AT-hook 2 gene (HMGA2) mRNA, in 53 formalin-fixed, paraffin-embedded mucoepidermoid carcinomas (MEC) and four normal parotid tissues using quantitative real-time RT-PCR (qPCR). MECs are often characterized by the fusion gene CRTC1-MAML2, the detection of which is an important tool for the diagnosis and prognosis of MEC. For detection of the CRTC1-MAML2 fusion transcript, we performed RT-PCR. The mean expression level of HMGA2 was higher in fusion negative (302.8 +/- 124.4; n = 14) than in positive tumors (67.3 +/- 13.1; n = 39). Furthermore, the fusion-negative tumors were often high-grade tumors and the HMGA2 expression level rose with the tumor grade (low: 43.7 +/- 11.0, intermediate: 126.2 +/- 28.3, and high: 271.2 +/- 126.5). A significant difference was found in the HMGA2 expression levels between the different grading groups (one-way ANOVA, P = 0.04) and among the fusion-negative and -positive tumors (t-test, P = 0.05), indicating that the expression level of HMGA2 was closely linked to grading, the presence/absence of the CRTC1-MAML2 fusion, and the tumor behavior of MECs. These findings offer further evidence for the theory that the MEC group comprises two subgroups: one group with the CRTC1-MAML2 fusion, which is a group with a moderate aggressiveness and prognosis, and the other group lacking that fusion corresponding to an increased stemness, and thus, higher aggressiveness and worse prognosis.

Mucoepidermoid carcinoma of the cervix: another tumor with the t(11;19)-associated CRTC1-MAML2 gene fusion

Mucoepidermoid carcinoma (MEC) of the uterine cervix is a controversial entity. By strict morphologic criteria, the tumor has features identical to those of salivary gland MEC and is characterized by nests composed of 3 cell types (epidermoid, intermediate, and mucin producing) in the absence of overt glandular differentiation. Nonetheless, the entity is not recognized in the current World Health Organization classification of cervical tumors. Given the morphologic similarity between MEC of the cervix and MEC of the salivary glands, we sought to determine if MEC of the cervix harbors the t(11;19)(q21;p13) characteristic of MEC of the major and minor salivary glands, a rearrangement that results in fusion of the cyclic adenosine 3',5' monophosphate coactivator CRTC1 to the Notch coactivator MAML2. We identified 7 cervical tumors from our departmental files and performed reverse transcription-polymerase chain reaction and fluorescence in situ hybridization-based molecular analysis for rearrangements of CRTC1 and MAML2; 14 conventional cervical adenosquamous carcinomas were used as controls. Analysis of the cervical MECs demonstrated a CRTC1-MAML2 fusion in 1 case, rearrangements of CRTC1 in 4 cases, and aberrations of MAML2 in 5 cases (rearrangements in 2 cases, amplification in 3 cases). All MEC showed aberrations of at least 1 of the loci, whereas none of the cervical adenosquamous carcinomas harbored rearrangements or amplification of either locus. Our results demonstrate that cervical tumors defined as MEC by strict morphologic criteria harbor genetic aberrations involving the genes characteristically rearranged in MEC of the salivary glands, and suggest that cervical MEC is an entity distinct from conventional cervical adenosquamous carcinoma. The development of drug therapy targeted to the genes rearranged in MEC underscores the importance of correct classification of cervical MEC because the diagnosis may hold therapeutic implications different from other cervical malignancies.

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.

A closer look at Warthin tumors and the t(11;19)

The translocation t(11;19)(q21;p13) has been described in mucoepidermoid carcinoma (MEC) and rarely in Warthin tumors (WT), both tumors of the salivary gland. The translocation creates a fusion gene in which exon 1 of CRTC1 is linked to exons 2-5 of MAML2. To verify the translocation in WT, we performed nested reverse transcriptase-polymerase chain reaction using RNA from 48 WTs. This revealed the t(11;19)(q21;p13) translocation and expression of the chimeric gene in two metaplastic WT samples, but in none of the remaining ordinary 46 WTs. On review, the two positive cases were classified as tumors highly suspect for MEC. Indeed, our experience and published observations of the t(11;19)(q21;p13) translocation in WT reveal that only a small subset of WTs are positive, and that these tumors are often classified as infarcted or metaplastic WT, known to overlap considerably with MEC on purely morphological grounds. We therefore conclude that the presence of the t(11;19)(q21;p13) rearrangement favors a diagnosis of MEC.

MECT1-MAML2 fusion transcript defines a favorable subset of mucoepidermoid carcinoma

PURPOSE

Mucoepidermoid carcinoma is the most common primary malignancy of the salivary gland. Mucoepidermoid carcinoma translocated gene 1-mastermind-like gene family (MECT1-MAML2) gene fusion was identified from a recurring t(11;19)(q21;p13) translocation, which is often the sole cytogenetic alteration in this disease. This fusion transcript has been frequently detected in mucoepidermoid carcinoma and shown to be involved in the transformation of epithelial cells. However, its clinicopathologic significance remains unclear.

EXPERIMENTAL DESIGN

Seventy-one cases of mucoepidermoid carcinoma and 51 cases of nonmucoepidermoid carcinoma salivary gland tumors (including 26 Warthin tumor cases) were retrospectively analyzed. RNA was extracted from archival materials: histologic paraffin specimens in all cases and cytologic specimens in 10 mucoepidermoid carcinoma cases. The MECT1-MAML2 fusion transcript was detected by a reverse transcription-PCR assay, which can be applied to both histologic and cytologic specimens. The presence of the fusion transcript was correlated with relevant clinicopathologic and survival data of the mucoepidermoid carcinoma patients.

RESULTS

The MECT1-MAML2 fusion transcript was detected in 27 of the 71 (38%) mucoepidermoid carcinoma cases but not in any case of nonmucoepidermoid carcinoma tumors. The reverse transcription-PCR results showed no difference between histologic and cytologic specimens. Detection of the MECT1-MAML2 fusion transcript was associated with a less advanced clinical stage and a low-grade tumor histology. The presence of the transcript was associated with longer disease-free and overall survivals on univariate analysis and emerged as an independent prognostic factor for longer overall survival on multivariate analysis.

CONCLUSIONS

The MECT1-MAML2 fusion transcript may be specific to mucoepidermoid carcinoma and associated with a distinct mucoepidermoid carcinoma subset that exhibits favorable clinicopathologic features and an indolent clinical course.

CRTC1/MAML2 fusion transcript in high grade mucoepidermoid carcinomas of salivary and thyroid glands and Warthin's tumors: implications for histogenesis and biologic behavior

We analyzed 55 primary salivary gland tumors including 22 mucoepidermoid carcinomas (MECs) to determine the association of MECT1/TORC1/CRTC1-MAML2 fusion transcript to tumor types, level of MEC differentiation and clinicopathologic parameters. Our primary salivary gland tumors were composed of 22 MECs, 11 Warthin's tumors, 10 adenoid cystic carcinomas, two basaloid carcinomas, five salivary duct carcinomas, and five adenocarcinomas, not otherwise specified. We also included, for the first time, three primary MECs of the thyroid gland. We used nested RT-PCR and subsequent sequencing techniques for detection and verification of the fusion transcript in fresh and archival specimens. Eighteen (81%) of the 22 primary salivary and one of the three thyroid glands with MEC were positive for the fusion transcript. The transcript was detected equally in low, intermediate and high grade as well as low and high stage MECs. Significant correlation between fusion negative tumors and distant metastasis was noted (P = 0.005). Four (36%) of the 11 Warthin's tumors were also positive for the transcript. None of the 22 primary non-MEC gland salivary carcinomas were positive for the transcript. We conclude that the CRTC1/MAML2 transcript may be detected in both low and high grade MEC, that fusion negative tumors may define a subset of biologically aggressive MEC's tumors, that the fusion is present in primary MECs of the thyroid gland and is also detectable in Warthin's tumor, and that a subset of MECs can be targeted for therapeutic intervention.

Frequent fusion of the CRTC1 and MAML2 genes in clear cell variants of cutaneous hidradenomas

Fusion of the CREB regulated transcription coactivator CRTC1 (a.k.a. MECT1, TORC1, or WAMTP1) to the Notch coactivator MAML2 is a characteristic feature of low-grade mucoepidermoid carcinomas of salivary and bronchial glands. The CRTC1-MAML2 fusion protein acts by inducing transcription of cAMP/CREB target genes, and this activity is crucial for the transforming properties of the protein. Here we show that the CRTC1-MAML2 gene fusion is also frequent in benign hidradenomas of the skin. FISH and RT-PCR analyses revealed that hidradenomas are genetically heterogeneous, and that 10 of the 20 tumors analyzed (50%) contained the CRTC1-MAML2 gene fusion and expressed the resulting fusion transcript. Immunohistochemical analysis demonstrated expression of the fusion protein in the majority of tumor cells, including clear cells, poroid cells, and cells with epidermoid and ductal differentiation. In addition, we could show that all fusion-positive tumors were morphologically distinguished by the presence of more or less abundant areas of clear cells whereas all fusion-negative tumors lacked clear cells. Our findings thus demonstrate that the CRTC1-MAML2 gene fusion is frequent in hidradenomas and is associated with clear cell variants of this tumor. Taken together, the present and previous observations indicate that the CRTC1-MAML2 fusion is etiologically linked to benign and low-grade malignant tumors originating from diverse exocrine glands rather than being linked to a separate tumor entity.

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.

Salivary mucoepidermoid carcinoma: revisited

Mucoepidermoid carcinoma (MEC) is a malignant epithelial neoplasm composed of varying proportions of mucous, epidermoid, intermediate, columnar, and clear cells and often demonstrates prominent cystic growth. MEC is usually subclassified as low, intermediate, or high grade on the basis of its histologic features, including the presence of cystic spaces, cellular differentiation, proportion of mucous cells, growth pattern, type of invasion, and cytologic atypia. Because even low-grade neoplasms may metastasize, the term mucoepidermoid tumor is inappropriate. The 3-level grading approach to tumor classification has found general acceptance among pathologists; differences in biologic behavior can be demonstrated even though clinical stage has become a better prognosticator. However, in the case of MEC, no universal agreement exists regarding which histologic grading criteria are most the useful, and grading has varied. These issues have led to the investigation of more subjective systems. We describe these new schemes, the histologic variants of MEC, and the ancillary methods that allow for further stratification of patients with MEC, especially for patients with grade 2 tumors, which have a variable and unpredictable clinical course.

Fusion oncogenes and tumor type specificity--insights from salivary gland tumors

Salivary gland tumors are frequently characterized by recurrent chromosome translocations, which have recently been shown to result in pathogenetically relevant fusion oncogenes. These genes encode novel fusion proteins as well as ectopically expressed normal or truncated proteins, and are found in both benign and malignant salivary gland tumors. The major targets of the translocations are DNA-binding transcription factors (PLAG1 and HMGA2) involved in growth factor signaling and cell cycle regulation, and coactivators of the Notch (MAML2) and cAMP (TORC1) signaling pathways. Identification of these fusion oncogenes has contributed to our knowledge of molecular pathways leading to epithelial tumors in general, and to salivary gland tumors in particular. Interestingly, the fusions in salivary gland tumors do not seem to be as tumor type specific as those in leukemias and sarcomas. Instead, they may function by activating basic transformation pathways that can function in multiple cell types. The downstream gene products of these fusions will be important targets for development of new intracellular therapeutic strategies.

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.

[Significance of molecular-cytogenetic findings in mucoepidermoid carcinoma as an example of salivary gland tumors]

Chromosome translocations in tumors frequently give rise to fusion genes encoding proteins with oncogenic activities. Mucoepidermoid carcinomas (MEC) are characterized by a t(11;19)(q21-22;p13) translocation found in approximately 60% of the tumors. This t(11;19) translocation results in a fusion gene consisting of exon 1 of the MECT 1 gene and exons 2-5 of the MAML 2 gene. As a result of the t(11;19) a fusion protein is generated which, independent of NOTCH-ligands, activates the transcription of the NOTCH target gene HES 1. The altered function of MAML 2 causes a disruption of NOTCH signalling which suggests a novel mechanism of tumorigenesis. Pending the elucidation of the t(11;19) at the molecular level of an apparently identical chromosomal translocation in Warthin's tumor, the identification of the translocation in MEC by FISH- and/or RT-PCR-analyses may become important in diagnosis and might have prognostic relevance. Warthin's tumors are benign salivary gland neoplasms with a distinctive histomorphology and histogenesis completely different from MEC.

Molecular assessment of allelic loss in Warthin tumors

Warthin's tumors are benign lesions of the head and neck that have a characteristic morphologic appearance. The etiology of Warthin's tumors is controversial and whether they are true neoplasms or developmental malformations continues to be debated. In this study, we examined 12 Warthin tumors with a molecular and immunohistochemical approach. Immunostains for p53 and p16ink were performed. The epithelial and lymphoid components of each lesion were microdissected and PCR was performed for 13 microsatellite markers at or near common tumor suppressor genes. The results were analyzed semiquantitatively using capillary electrophoresis. Frequency of allelic loss was calculated. The epithelial component of all tumors was negative for p53 and p16ink. By molecular genotyping there was only one case that had one locus with allelic imbalance, while the remainder had no evidence of clonal allelic loss. The immunohistochemical and molecular results in this study lend support to the hypothesis that Warthin tumors are non-neoplastic, as there was no evidence of aberrant staining for tumor suppressor gene protein products and no evidence of consistent clonal allelic losses.

Clear cell hidradenoma of the skin-a third tumor type with a t(11;19)--associated TORC1-MAML2 gene fusion

Recent studies have shown that the t(11;19)(q21;p13) translocation in mucoepidermoid carcinomas and benign Warthin's tumors results in a fusion of the N-terminal CREB-binding domain of the cAMP coactivator TORC1 (a.k.a. MECT1 and WAMTP1) to the Notch coactivator MAML2. Here we show that a third tumor type, clear cell hidradenoma of the skin, also expresses this gene fusion. RT-PCR analysis of a clear cell hidradenoma with a t(11;19)(q21;p13) translocation revealed expression of a TORC1-MAML2 fusion transcript consisting of exon 1 of TORC1 fused to exons 2-5 of MAML2. Because the fusion was only detected in a single case, the frequency of this aberration in clear cell hidradenomas remains unknown. These results demonstrate that the t(11;19) in mucoepidermoid carcinoma, Warthin's tumor, and clear cell hidradenoma targets the same genes and results in identical gene fusions, indicating that at least subgroups of these glandular tumors evolve through activation of the same molecular pathways.

A study of MECT1-MAML2 in mucoepidermoid carcinoma and Warthin's tumor of salivary glands

The t(11;19)(q21;p13) chromosomal translocation has been described in two distinct types of salivary gland neoplasms: mucoepidermoid carcinoma (MEC) and Warthin's tumor (WT). Since this translocation has been recently shown to generate a MECT1-MAML2 fusion gene, we evaluated 10 primary MEC and seven primary WT to further define the molecular association of these two entities using cytogenetic, as well as in situ hybridization (ISH) and reverse transcriptase-polymerase chain reaction (RT-PCR) analyses directed against the fusion gene. A karyotype was established in all neoplasms except for two MEC cases. Of the eight karyotyped MECs, five showed the t(11;19)(q21;p13), two had a normal karyotype, and one case presented a -Y and +X. Three of the WT revealed a normal karyotype and four had several abnormalities which did not involve chromosomes 11 and 19. ISH analysis performed in cytogenetic suspension and/or in tumor paraffin sections demonstrated MAML2 rearrangement in 7 of 10 cases of MEC: all five cases with t(11;19), one case with normal karyotype, and one unkaryotyped case. RT-PCR analysis confirmed the expression of the MECT1-MAML2 gene in all MEC cases that were positive by ISH analysis. Neither the t(11;19) nor MECT1-MAML2 was detected in any case of WT, nor in control samples from polymorphous low-grade adenocarcinoma, acinic cell carcinoma, or normal parotid gland tissue. We have demonstrated that ISH and RT-PCR are sensitive methods for detecting MECT1-MAML2 in MEC. In contrast, we did not detect the t(11;19) nor MECT1-MAML2 expression in seven cases of WT.

False diagnosis caused by Warthin tumor of the parotid gland combined with actinomycosis

A case is reported in which a unilateral parotid gland cystadenolymphoma was combined with actinomycosis. A 48-year-old woman presented with a mass in the left parotid region and paresis of the lower left palpebra. The computed tomography, echography, and parotid radiographic findings did not exclude a neoplasm of the left parotid gland. The ramus of the mandible was involved in the process. Intraoperative freezing histology, total parotidectomy, and partial mandibulectomy were performed, with sacrifice of the facial nerve followed by nerve reconstruction. The final histological evaluation was Warthin tumor with actinomycosis. Four years after treatment, the patient is free of disease. No similar cases seem to have been reported thus far.

Relative paucity of gross genetic alterations in myoepitheliomas and myoepithelial carcinomas of salivary glands

The diagnosis of salivary gland myoepithelioma, an entity with heterogeneous cytomorphology and inconsistent immunophenotype, rests on conventional histology. However, the clinical course cannot be predicted reliably from cytomorphological and immunophenotypic analysis. The present study determined the immunophenotype of a representative series of 12 myoepitheliomas and 21 malignant myoepitheliomas. Among the seven markers tested, antibodies against cytokeratins 5/6, S-100 protein, and vimentin produced the most consistent reactivity profile. Comparative genomic hybridization (CGH) profiles of 12 myoepitheliomas showed chromosomal losses in three of 12 cases. In myoepithelial carcinomas, however, ten of 19 tissues investigated by CGH lacked detectable cytogenetic aberrations. In five cases, aberrations involved chromosome 8, in line with observations in salivary gland carcinomas of other differentiation. One case that was represented in three separately localized manifestations of the disease proved informative as to the relevance of gross aberration for tumour development, as these tumours differed in their CGH profiles. Staining for cytokeratins 5/6 is a useful addition to the established immunohistological marker panel in the work-up of myoepitheliomas, because of its reliable expression in most cases and because it may underline the epithelial nature of the lesion. CGH proved to be of limited value as a diagnostic adjunct; the presence of numerous gross cytogenetic aberrations should raise the suspicion of malignancy. The low frequency of aberrations detectable by CGH in overtly malignant myoepithelial neoplasms suggests that gross cytogenetic alterations were acquired in the course of tumour progression and points to the relevance of genetic changes not resolved by CGH.

Upper respiratory tract carcinoma with chromosomal translocation 15;19: evidence for a distinct disease entity of young patients with a rapidly fatal course

BACKGROUND

Carcinoma of the upper respiratory tract is rare in childhood, and cytogenetic aberrations have not been characterized in this population. The chromosomal translocation 15;19 has been reported four times previously. All patients were young and had tumors arising in the thorax. The three reports that provide clinical follow-up all describe superior vena cava syndrome and death soon after presentation. All tumors were diagnosed as carcinoma (three undifferentiated, one mucoepidermoid), and the authors suggested thymus, lung, or germ cell origin.

METHODS

The authors investigated the clinical and pathologic findings in two patients with poorly differentiated carcinoma showing evidence of t(15;19). This included a 13-year-old girl with a rapidly growing epiglottic mass, leading to superior vena cava syndrome and death and a 12-year-old girl with an aggressive nasopharyngeal mass showing intracranial extension.

RESULTS

The laryngeal tumor was poorly differentiated, with vesicular nuclei, prominent nucleoli, extensive necrosis, and a lymphoplasmacytic infiltrate; cells were positive for cytokeratin and negative for lymphoma, melanoma, germ cell, and endocrine markers. Electron microscopy showed rare intermediate junctions and basal lamina. The nasopharyngeal tumor was poorly differentiated with areas of obvious squamous differentiation observed histologically, immunophenotypically, and ultrastructurally. Cytogenetic and fluorescent in situ hybridization studies were consistent with t(15;19)(q13;p13.1) in both cases. Both children received chemo- and radiotherapy. The first child died of disease after 36 weeks; autopsy revealed tumor in the larynx with spread to the skin/subcutis (neck and thorax) and lymph nodes (cervical, subcarinal, and pulmonary hilar). The second child developed widespread bony metastases and died of disease after 13 weeks.

CONCLUSIONS

In conjunction with previous reports, the authors' findings show that t(15;19) is part of a distinct clinicopathologic entity characterized by young age, midline carcinoma of the neck or upper thorax, and a rapidly fatal course. Female gender and superior vena cava syndrome are common. The histogenesis of these distinctive tumors is unknown. The authors' findings suggest origin in the upper airway, perhaps from submucosal glands.

High-resolution DNA flow cytometry in papillary cystadenoma lymphomatosum (Warthin's tumour)

Twenty-eight examples of papillary cystadenoma lymphomatosum (Warthin's tumour) of the parotid gland were analysed by high-resolution DNA flow cytometry. The mean coefficient of variation was found to be 1.19% (SD: 0.41). All tumours were DNA diploid. These results did not correspond with expected deviations based on published chromosomal studies. Also, the homogeneously low S-phase fractions (mean: 4.8%; SD: 2.7) found did not support the hypothesis of etiologically distinctive subgroups in these tumours.

Cytogenetic characterisation of Warthin's tumour

Warthin's tumour is a peculiar subtype of monomorphic adenomas of the salivary glands, frequently cystic, and that characteristically associates an epithelial glandular cell component to a dense lymphoid infiltrate. Short-term cultures from 12 Warthin's tumours of salivary glands, including 5 previously reported cases were successfully karyotyped and clonal numerical and/or structural changes were detected in 7 of them (58%). 3 cases showed numerical abnormalities with loss of chromosomes Y (2 cases) and X (1 case). The remaining 4 abnormal cases presented the following structural changes: complex translocation t(11;19;16)(q21;p12;p13.3); reciprocal translocations t(6;8)(p23;q22) and t(6;15)(p21;q15) (2 cases); and 1p22, 3p26, 11p13 changes. In 1 case, clonal numerical deviations (+ 7 and -Y) were concurrent with the structural rearrangement t(6;8). Two of these aberrations are suggested to be Warthin's tumour-associated: 11q;19p translocation has already been described in 3 cases, and structural rearrangements of 6p23 have also been reported in another case. Our study extends the cytogenetic information about Warthin's tumour and identifies two recurrent abnormalities --6p rearrangements and t(11;19)--specific for this salivary neoplasm.

A mucoepidermoid carcinoma of minor salivary gland with t(11;19)(q21;p13.1) as the only karyotypic abnormality

We present the cytogenetic analysis of a mucoepidermoid carcinoma of the minor salivary gland with t(11,19)(q21;p13.1) as the sole karyotypic abnormality. Our findings, along with those of previous reports, indicate that this translocation is an early and most likely a primary event in the development of a least a subset of these neoplasms.

Benign salivary gland tumors: a cytogenetic study of 21 cases

Cytogenic findings of 21 benign salivary gland tumors, including 14 pleomorphic adenomas, 5 Warthin's tumors, 1 myoepithelioma, and 1 cystadenoma, are reported. The present study confirms that pleomorphic adenomas characteristically have highly specific rearrangements involving only a few chromosome regions (3p21, 8q12 and 12q13-15) which suggests their specific role in the mixed tumor genesis. Warthin's tumors also show non-random numerical and structural alterations that were concurrent in one of the cases studied. To our knowledge no cytogenetic data are available in myoepitheliomas and cystadenomas. The former reveals a normal karyotype and the latter shows only clonal numerical alterations (gain of chromosomes 2 and 18).

Cytogenetic heterogeneity in a clear cell hidradenoma of the skin

Short-term cultures from a clear cell hidradenoma, a benign skin tumor for which no chromosome data exist, were cytogenetically analyzed. A total of eight unrelated aberrant clones were identified. The karyotypic profiles of two separately processed parts of the sample--a tumor nodule and seemingly normal adjacent dermal tissue--were different. Characteristic for the tumor nodule was a single abnormal clonal population consisting of three subclones: 46,XY,der(2)inv(2)(p13q23)t(2;9)(p13;q22), der(9)t(2;9)(q23;q22),t(11;19)(q21;p13),t(12;19)(q24;p13)/46,idem, inv(1)(p32q44)/92,idemx2. The adjacent tissue contained, in addition to the clone found in the tumor nodule, a spectrum of unrelated clones, the largest of which also showed clonal evolution: 45-47,XY,t(3;6)(p25;p25),t(12;17)(q15;q12),-17,+r(17)x2 [cp]/45-47,idem,inv(5)(p15q22)/90-94,idemx2. The remaining six clones found in this part were small and had simpler numerical or structural aberrations. The multiclonal pattern observed in this hidradenoma seems to reflect both cytogenetic convergence and divergence during neoplastic progression. The presence of unrelated clones may be an indication that the tumor was of multicellular origin.

Cytogenetic observations in 13 cystadenolymphomas (Warthin's tumors)

The cytogenetic findings in 13 cultured Warthin's tumors (papillary cystadenoma lymphomatosum) are reported. Only one case showed an abnormal stemline. This was pseudodiploid and characterized by three different reciprocal translocations and one deletion. Small abnormal sidelines, however, were seen in three additional cases. All except one of the 12 tumors with a normal stemline contained variant cells. These showed a variety of numerical and/or structural aberrations. From this study it is obvious that to determine whether or not cytogenetically distinctive subgroups actually exist in cystadenolymphomas (as in pleomorphic adenomas) the number of cases must be greatly amplified.

Non-random chromosome rearrangements in adenoid cystic carcinoma of the salivary glands

The chromosomal findings in 10 adenoid cystic carcinomas (ACC) of the salivary glands are described. Clonal numerical deviations as the sole anomaly were detected in four cases and structurally rearranged stemlines and sidelines in four cases. An apparently identical t(6;9)(q23;p21) was found in two tumors; in one case the translocation was part of the abnormal stemline and in the other case it was the sole anomaly in a single variant cell. A similar or identical t(6;9)(q21-24;p13-23) has recently been reported in three of 15 previously published cases of ACC. The three remaining tumors with abnormal stemlines all had rearrangements of chromosome 9, including t(1;9)(q21;p21-22), der(9)i(9)(q10)inv(9)(q12q13), and der(X)t(X;9)(p21;p22-23), respectively. The latter case also had a t(17;18)(p12;q11.2) that was common to both abnormal clones present in this tumor. In addition to other abnormalities, the clone with der(X)t(X;9) also showed a del(6)(q13q21). In two cases fluorescence in situ hybridization (FISH) was used for further characterization of the marker chromosomes. A survey of the present findings together with previous results from 15 ACC clearly demonstrates that rearrangements of 6q21-24 (deletions or translocations in 11 cases), 9p13-23 (translocations in seven cases), and 17p12-13 (translocations in three cases) are recurrent, and often primary, in ACC, and that the t(6;9)(q21-24;p13-23), found in five tumors, is a non-random, primary aberration.

Recurrent rearrangements of 11q14-22 in mucoepidermoid carcinoma

We describe the cytogenetic findings in five mucoepidermoid carcinomas (MEC) of the major and minor salivary glands. Three of the five tumors analyzed showed an apparently identical t(11;19)(q14-21;p12). In one case, the t(11;19) was the only common clonal abnormality, while in the other two cases the translocation was found together with +16, +20, and inv(1)(p32-33q42), t(6;15)(p12;q25), respectively. The latter case also showed an interstitial short arm deletion of the der(11) chromosome. Of the two remaining cases, one had a del(3)(p13p23) as the sole karyotypic abnormality, while the other had a hyperdiploid stemline characterized by the following numerical deviations: +2, +5, +6, +7, +8, +17, +18, and +19. These findings, together with previously published data from seven from seven MEC, indicate that at least two different, partially overlapping cytogenetic subgroups exist: 1) cases with structural rearrangements of 11q14-22; the finding of three tumors with an apparently identical t(11;19)(q14-21;p12) demonstrates that this is a non-random, and possibly primary abnormality in MEC, and 2) single or multiple trisomies, either observed as the sole anomalies or in combination with structural rearrangements.