Cytogenetic similarities between two types of salivary gland carcinomas: adenoid cystic carcinoma and polymorphous low-grade adenocarcinoma

Development of head and neck pathology in Europe

This review gives a brief history of the development of head and neck pathology in Europe from a humble beginning in the 1930s to the explosive activities the last 15 years. During the decades before the introduction of immunohistochemistry in the 1980s, head and neck pathology grew as a subspeciality in many European countries. In the late 1940s, the Institute of Laryngology and Otology with its own pathology laboratory was founded in London, and in 1964 the World Health Organization (WHO) International Reference Centre for the Histological Classification of Salivary Tumours was established at the Bland-Sutton Institute of Pathology, also in London. International collaboration, and very much so in Europe, led to the publication of the first WHO Classification of Salivary Gland Tumours in 1972. In the 1960s, a salivary gland register was organised in Hamburg and in Cologne the microlaryngoscopy was invented enabling microscopic endoscopic examination and rather shortly afterwards a carbon dioxide laser attached to the microscope became established and laryngeal lesions could be treated by laser vaporisation. During the last three decades, the use of immunohistochemistry supplemented with cytogenetic and refined molecular techniques has greatly facilitated the pathological diagnostics of head and neck lesions and has had a huge impact on research. Collaboration between different European centres has drastically increased partly due to establishment of scientific societies such as the Head and Neck Working Group (HNWG) within the European Society of Pathology and the International Head and Neck Scientific Group (IHNSG). A very large number of European pathologists have contributed to the 2nd, 3rd and 4th WHO books, and are involved in the upcoming 5th edition. Accredited educational meetings and courses are nowadays regularly arranged in Europe. Numerous textbooks on head and neck pathology have been written and edited by European pathologists. The increased collaboration has created larger series of tumours for research and new entities, mainly defined by their genetic abnormalities, are continuously emerging from Europe, particularly regarding salivary gland neoplasms and "undifferentiated" sinonasal tumours. These findings have led to a better and more precise classification and open the possibilities for new treatment strategies.

Novel PRKD gene rearrangements and variant fusions in cribriform adenocarcinoma of salivary gland origin

Polymorphous low-grade adenocarcinoma (PLGA) and cribriform adenocarcinoma of minor salivary gland (CAMSG) are low-grade carcinomas arising most often in oral cavity and oropharynx, respectively. Controversy exists as to whether these tumors represent separate entities or variants of one spectrum, as they appear to have significant overlap, but also clinicopathologic differences. As many salivary carcinomas harbor recurrent translocations, paired-end RNA sequencing and FusionSeq data analysis was applied for novel fusion discovery on two CAMSGs and two PLGAs. Validated rearrangements were then screened by fluorescence in situ hybridization (FISH) in 60 cases. Histologic classification was performed without knowledge of fusion status and included: 21 CAMSG, 18 classic PLGA, and 21 with "mixed/indeterminate" features. The RNAseq of 2 CAMSGs showed ARID1A-PRKD1 and DDX3X-PRKD1 fusions, respectively, while no fusion candidates were identified in two PLGAs. FISH for PRKD1 rearrangements identified 11 additional cases (22%), two more showing ARID1A-PRKD1 fusions. As PRKD2 and PRKD3 share similar functions with PRKD1 in the diacylglycerol and protein kinase C signal transduction pathway, we expanded the investigation for these genes by FISH. Six additional cases each showed PRKD2 and PRKD3 rearrangements. Of the 26 (43%) fusion-positive tumors, there were 16 (80%) CAMSGs and 9 (45%) indeterminate cases. A PRKD2 rearrangement was detected in one PLGA (6%). We describe novel and recurrent gene rearrangements in PRKD1-3 primarily in CAMSG, suggesting a possible pathogenetic dichotomy from "classic" PLGA. However, the presence of similar genetic findings in half of the indeterminate cases and a single PLGA suggests a possible shared pathogenesis for these tumor types.

An update on molecular diagnostics of squamous and salivary gland tumors of the head and neck

CONTEXT

Molecular testing in anatomic pathology is becoming standardized and can contribute valuable diagnostic, therapeutic, and prognostic information for the clinical management of patients. In head and neck pathology, recent advances in molecular testing have provided important targets in several different diagnostic areas, with particular emerging clinical applications in squamous and salivary gland pathology. In squamous mucosal-derived lesions, human papilloma virus has emerged as an important pathogenic etiology in a subset of oropharyngeal squamous cell carcinomas. Within the category of salivary gland tumors, 3 tumors have recently been recognized that contain oncogenic translocations.

OBJECTIVE

To describe the current state of information about the molecular alterations in squamous lesions and in salivary gland tumors of the head and neck.

DATA SOURCES

Published literature on squamous and salivary gland tumors of the head and neck.

CONCLUSIONS

The different approaches to identification of viral-associated tumors include assays using polymerase chain reaction, in situ hybridization, and immunohistochemistry. Most mucoepidermoid carcinomas harbor MECT1-MAML2 gene rearrangement. The MYB-NFIB translocations have recently been identified in adenoid cystic carcinomas. Finally, a newly described tumor of salivary gland, mammary analogue secretory carcinoma, harbors the ETV6-NTRK3 translocation. Although these translocations are just emerging as diagnostic targets, future roles may evolve as potential therapeutic targets.

Comprehensive analysis of the MYB-NFIB gene fusion in salivary adenoid cystic carcinoma: Incidence, variability, and clinicopathologic significance

PURPOSE

The objectives of this study were to determine the incidence of the MYB-NFIB fusion in salivary adenoid cystic carcinoma (ACC), to establish the clinicopathologic significance of the fusion, and to analyze the expression of MYB in ACCs in the context of the MYB-NFIB fusion.

EXPERIMENTAL DESIGN

We did an extensive analysis involving 123 cancers of the salivary gland, including primary and metastatic ACCs, and non-ACC salivary carcinomas. MYB-NFIB fusions were identified by reverse transcriptase-PCR (RT-PCR) and sequencing of the RT-PCR products, and confirmed by fluorescence in situ hybridization. MYB RNA expression was determined by quantitative RT-PCR and protein expression was analyzed by immunohistochemistry.

RESULTS

The MYB-NFIB fusion was detected in 28% primary and 35% metastatic ACCs, but not in any of the non-ACC salivary carcinomas analyzed. Different exons in both the MYB and NFIB genes were involved in the fusions, resulting in expression of multiple chimeric variants. Notably, MYB was overexpressed in the vast majority of the ACCs, although MYB expression was significantly higher in tumors carrying the MYB-NFIB fusion. The presence of the MYB-NFIB fusion was significantly associated (P = 0.03) with patients older than 50 years of age. No correlation with other clinicopathologic markers, factors, and survival was found.

CONCLUSIONS

We conclude that the MYB-NFIB fusion characterizes a subset of ACCs and contributes to MYB overexpression. Additional mechanisms may be involved in MYB overexpression in ACCs lacking the MYB-NFIB fusion. These findings suggest that MYB may be a specific novel target for tumor intervention in patients with ACC.

Translocation t(6;14) as the sole chromosomal abnormality in adenoid cystic carcinoma of the base of tongue

We present an adenoid cystic carcinoma of the base of tongue in a 48-year-old male with a restricted chromosomal alteration by cytogenetic and spectral karyotypic analysis (SKY). SKY and G-banding analyses identified the t(6;14)(q25;q13) as the sole structural aberration in all metaphases analyzed. This finding supports a critical role for this event in the development of this tumor. The implications of chromosome 6q translocation in this case and in previously reported adenoid cystic carcinomas are highlighted and discussed.

DNA copy number gains at loci of growth factors and their receptors in salivary gland adenoid cystic carcinoma

PURPOSE

Adenoid cystic carcinoma (ACC) is a malignant salivary gland tumor with a high mortality rate due to late, distant metastases. This study aimed at unraveling common genetic abnormalities associated with ACC. Additionally, chromosomal changes were correlated with patient characteristics and survival.

EXPERIMENTAL DESIGN

Microarray-based comparative genomic hybridization was done to a series of 18 paraffin-embedded primary ACCs using a genome-wide scanning BAC array.

RESULTS

A total of 238 aberrations were detected, representing more gains than losses (205 versus 33, respectively). Most frequent gains (>60%) were observed at 9q33.3-q34.3, 11q13.3, 11q23.3, 19p13.3-p13.11, 19q12-q13.43, 21q22.3, and 22q13.33. These loci harbor numerous growth factor [fibroblast growth factor (FGF) and platelet-derived growth factor (PDGF)] and growth factors receptor (FGFR3 and PDGFRbeta) genes. Gains at the FGF(R) regions occurred significantly more frequently in the recurred/metastasized ACCs compared with indolent ACCs. Furthermore, patients with 17 or more chromosomal aberrations had a significantly less favorable outcome than patients with fewer chromosomal aberrations (log-rank = 5.2; P = 0.02).

CONCLUSIONS

Frequent DNA copy number gains at loci of growth factors and their receptors suggest their involvement in ACC initiation and progression. Additionally, the presence of FGFR3 and PDGFRbeta in increased chromosomal regions suggests a possible role for autocrine stimulation in ACC tumorigenesis.

Mapping of candidate tumor suppressor genes on chromosome 12 in adenoid cystic carcinoma

Adenoid cystic carcinoma (ACC) is a common malignancy of salivary glands, for which the underlying genetic mechanisms of tumorigenesis are poorly understood. Prior studies in ACC have identified deletions in chromosome 12. To further characterize these changes, we performed an extensive LOH analysis in 58 ACC using a panel of 28 microsatellite markers. Results show 66% overall genetic loss. Three markers (D12S1713, D12S2196, D12S398) are contiguous and define a 6.84 Mb region of deletion at 12q13.11-q13.13. Two other markers (D12S2078, D12S1628) are also contiguous and define a 4.5 Mb region of deletion at 12q24.32-q24.33. The three remaining markers, D12S1056 at 12q14.1, D12S1051 at 12q23.1 and D12S1636 at 12q23.3 define smaller regions of deletion. An analysis of microarray gene expression profiling data available for ACC shows several genes with significant transcriptional downregulation that map to these areas of genetic deletion. This combined genetic and genomic analysis provides several candidate genes to test for functional tumor suppressor activity in ACC.

Management of paranasal sinus malignancy

Malignancies of the nasal cavity and paranasal sinuses represent a wide spectrum of histologies, tissues of origin, and anatomic primary sites. The inherent difficulty in generalizing treatment approaches is obvious, given the numerous variables associated with the broadly-based term, paranasal sinus malignancy (PNSCa). Nevertheless, the majority of epithelial and salivary malignancies of this region (ie, squamous cell carcinoma, adenocarcinoma, adenoid cystic carcinoma, sinonasal undifferentiated carcinoma, and esthesioneuroblastoma) require surgical intervention as part of any treatment regimen. Recent trends have broadened the indications for chemotherapeutic and radiotherapeutic options in the management of advanced PNSCa. Nonepithelial malignancies, including the wide variety of sarcomas arising in this region, most commonly require multimodality treatment including chemotherapy, radiation, and/or surgery for definitive treatment. Moreover, the proximity of the nasal cavity and paranasal sinuses to structures including the orbit, dura, brain, cranial nerves, and carotid arteries mandates careful radiologic and neurologic evaluations throughout the course of the disease. Surgical advances now permit complex tumor removal and reconstruction surrounding these structures resulting in functional and cosmetic improvements when compared to earlier techniques. However, additional clinical trials are necessary to systematically evaluate the locoregional control, organ-preservation strategies, and survival related to the variety of treatments currently available.

Polymorphous low-grade adenocarcinoma—a rare and aggressive entity in adolescence

Polymorphous low-grade adenocarcinoma (PLGA) is an uncommon tumour that usually affects the minor salivary glands, particularly in the palate. It is rare in young patients, and here we report a case in a teenage girl. She presented at the age of 16, although the lesion had been noticed 2 years previously. The tumour showed histopathological features of PLGA, but recurred locally, behaved aggressively, and ultimately metastasised to cervical lymph nodes. This was accompanied by an altered histological picture, with a papillary cystic pattern and necrosis becoming progressively more prominent. PLGA is not always a low-grade lesion and some tumours, notably those with a papillary cystic growth pattern, may require more aggressive treatment.

Comparative genomic hybridization in primary sinonasal adenocarcinomas

BACKGROUND

Little is known about the genetic alterations that occur in sinonasal adenocarcinomas. The goal of the current study was to detect recurrent chromosomal gains and losses in a series of 21 primary sinonasal adenocarcinomas using comparative genomic hybridization (CGH).

METHODS

The authors examined ethmoid sinus adenocarcinoma samples from 21 patients. All 21 adenocarcinomas were associated with work-related exposure to wood dust. CGH was used to detect chromosomal abnormalities, and the results of CGH analysis were evaluated for correlations with clinicopathologic characteristics.

RESULTS

Chromosomal gains and losses were detected in all 21 adenocarcinomas. Gains were detected at high frequencies at 7q11-21 (n = 15 [71%]), 18p11 (n = 14 [66%]), 8q11-22 (n = 13 [62%]), 5p11-13 (n = 12 [57%]), 12q11-13 and 19p (n = 11 [52%]), 20q (n = 10 [47%]), X and 5p (n = 9 [43%]), and 3q26-27 (n = 8 [38%]); and losses were detected at 8p22-23 (n = 18 [86%]), 18q22-23 (n = 17 [80%]), 17p13 (n = 12 [57%]), and 5q31-qter (n = 11 [52%]). Aside from low-level gains, 43 high-level amplifications were observed in the current series of 21 tumors, most commonly at Xq13 (n = 7 [33%]).

CONCLUSIONS

CGH revealed that ethmoid sinus adenocarcinomas carry a large number of chromosomal losses and gains, including high-level amplifications. To the authors' knowledge, the current study represents the first attempt to investigate sinonasal adenocarcinomas on a genetic level by using CGH. The pattern of chromosomal abnormalities in these tumors was different from the pattern in other tumors within the same anatomic region (e.g., squamous cell carcinomas and salivary gland tumors); this finding may be explained by differences in etiology. Nonetheless, sinonasal adenocarcinomas appear to be genetically similar to adenocarcinomas of the stomach and colon, which also have an etiology that differs from that of sinonasal adenocarcinomas. Further study is necessary to better understand the molecular genetic basis underlying the development of sinonasal adenocarcinomas. In the near future, this type of understanding may present new possibilities for prevention and treatment of malignant disease.

Salivary-type neoplasms of the breast and lung

Salivary-type tumors occur in multiple sites in the human body, likely related to a basic structural homology between exocrine glands in these different anatomic areas. This paper reviews these salivary gland tumor types in breast tissue and lung. Salivary-type tumors of both breast and lung are relatively uncommon in comparison to their salivary gland counterparts. This may be attributable in part to lack of familiarity with these tumors in extra-salivary sites, and in part to histologic overlap with other primary and metastatic tumor types. Recognition of these entities is improving as the clinical and pathologic features are better delineated, and tumors are more accurately classified. Prediction of malignant behavior is not always possible in these unusual sites. In some instances, such as adenoid cystic carcinoma, behavior is known to differ considerably from that of analogous primary salivary gland tumors and in other instances there are simply too few reported cases to allow for adequate prognostication. In fact, more recent papers discuss the need to consider a spectrum encompassing benign and malignant lesions, in both breast and lung. Of course, some entities show clear-cut evidence of malignancy with documented potential for metastasis, others show bland features and well-reported benign behavior, and the less well-defined entities reside between these two extremes. The molecular pathology of salivary gland tumors has been reasonably well investigated in that location; however; there are few molecular studies devoted to salivary-type tumors of the breast and lung. This represents a potential area for future growth in further clarifying these tumors and their behavior.