Use of fluorescence in situ hybridization (FISH) to distinguish intranodal nevus from metastatic melanoma

Benign Islet Cells Within Peripancreatic Lymph Nodes: A Potential Diagnostic Pitfall

The presence of epithelial cells within lymph node parenchyma is typically indicative of a metastatic malignancy. However, there are rare instances in which non-neoplastic epithelial or epithelioid cells may be found within lymph nodes, either due to aberrant embryologic migration, mechanical displacement, or physiological trafficking. These can potentially lead to serious potential diagnostic pitfalls, as when such situations are encountered by surgical pathologists, there is substantial risk of overdiagnosing these as metastatic malignancy. Herein, we describe 2 cases of benign pancreatic islet cells within peripancreatic lymph nodes, and underscore the potential for misdiagnosis of this phenomenon as foci of metastatic well-differentiated neuroendocrine tumor. The benign nature of these intranodal islet cells was supported by: (1) the absence of a well-differentiated neuroendocrine tumor in the entirely submitted concomitant pancreatic resection specimen and (2) the presence of an admixture of insulin and glucagon expressing cells by immunohistochemistry in a distribution characteristic of non-neoplastic pancreatic islets. Both cases were incidental microscopic findings in pancreatic resections for intraductal papillary mucinous neoplasms that were previously biopsied and showed associated microscopic areas of fibrosis and chronic pancreatitis and thus this phenomenon may be related to mechanical displacement from prior injury and/or biopsy.

Ancillary testing for melanoma: current trends and practical considerations

The diagnosis of melanocytic lesions is aided by ancillary testing, but clinical inspection with the histomorphological assessment on biopsy remains sufficient in most cases. Immunohistochemistry and molecular studies have proven useful for diminishing the pool of histomorphologically borderline lesions, and sequential testing may further improve overall diagnostic performance, but these assays should be used in a stepwise fashion if at all. Ancillary tests vary based on their technology, performance, and practical considerations, including but not limited to the specific diagnostic question, cost, and turn-around time, which impact test selection. This review examines currently used ancillary tests for the purpose of characterizing melanocytic lesions. Both scientific and practical considerations are discussed.

Correlation of FISH and PRAME Immunohistochemistry in Ambiguous Superficial Cutaneous Melanocytic Proliferations

ABSTRACT

Preferentially expressed antigen in melanoma (PRAME) is a tumor-associated repressor of retinoic acid signaling which is expressed in melanoma and has emerged as a potential biomarker for malignant behavior in melanocytic neoplasms. Although ancillary molecular techniques such as fluorescence in situ hybridization (FISH) are established techniques in the diagnosis of problematic cutaneous melanocytic proliferations, they are expensive, time-consuming, and require appropriate infrastructure, which places them out of reach of some laboratories. The advent of readily available commercial antibodies to PRAME has the potential to provide a more accessible alternative. The aim of this study was to determine whether immunohistochemistry for PRAME could serve as a surrogate for FISH analysis in a subgroup of challenging superficial melanocytic proliferations. Cases which had previously been submitted for FISH analysis were stained for PRAME and interpreted by a panel of at least 3 dermatopathologists is a blinded fashion. Of a study set of 55 cases, 42 (76%) showed a pattern of PRAME immunostaining which was concordant with the cytogenetic interpretation, with an unweighted kappa of 0.42 (representing mild-to-moderate agreement). Thus, although there was a correlation between positive immunohistochemistry for PRAME and abnormal findings on FISH analysis, in our view, the concordance was not sufficient to enable PRAME immunohistochemistry to act as a surrogate for FISH testing. Our findings reiterate the principle that interpretation of problematic superficial melanocytic proliferations requires a synthesis of all the available data, including clinical scenario, morphological features, immunohistochemistry, and ancillary molecular investigations.

Current concepts of ectopic nodal inclusions with special emphasis on nodal nevi

Nodal inclusions of ectopic tissue within lymph nodes are seen comparatively often in dermatopathology and general pathology. Glandular and nonglandular epithelium, as well as melanocytic nevi can be observed within lymph nodes and represent mostly incidental findings without any relevance. The main challenge in reporting these morphologic features is to differentiate such benign inclusions from metastatic settlements of distinct organ tumors. As sentinel node biopsy and lymph node dissection have become standard procedure in clinical oncology and have an immense clinical impact, the correct evaluation of these nodal inclusions is indispensable to avoid undertreatment or overtreatment of patients. In addition, the genesis of these inclusions has not yet been satisfactorily clarified. Two concepts have been laid out: the theory of benign metastases and the migration arrest theory. However, neither theory has so far been able to answer the following questions: Why do we find more nodal nevi in patients with melanoma who had a sentinel node biopsy than in patients without melanoma, and why do we not find nodal nevi in deep visceral lymph nodes? We present a comprehensive review of the current knowledge on nodal inclusions, proposing a concept for the pathogenesis of nodal nevi, to answer these questions.

Nevus cell aggregates massively occupying parenchyma of an external iliac lymph node: A case report and review of the literature

We report a case of nevus cell aggregates (NCAs) in an external iliac lymph node from a patient with a compound congenital nevus in the corresponding drainage skin. Melanocytes in parenchyma were in band, nest-like or nodular fashion, and partly continuous with those in capsule and trabeculae. The largest nodule in parenchyma measured 6.5 mm. Melanocytes mostly exhibited benign appearance identical to cutaneous nevus. A few regions abundant in cells displayed atypical features, including increased nucleo-cytoplasmic ratio, small nucleoli, and occasional mitotic figures. Immunohistochemistry showed that melanocytes stained positive for p16, but negative for HMB-45 and nestin. Ki-67 labeling was less than 1% and reticulin mainly surrounded individual melanocytes. Besides, Vysis melanoma fluorescence in situ hybridization (FISH) plus another 2 probes targeting 9p21(CDKN2A) and 8q24(MYC) showed normal results. The patient is alive without malignant tumor after 52-month follow up. Our case provides a new evidence for the existence of intraparenchymal NCAs in deep lymph node and indicates that melanocytes with some atypical features can occur in nodal nevi. Nevus cells in parenchyma connected to those in capsule and trabeculae are a significant clue to distinguish nodal nevi from metastatic melanomas. Additionally, immunohistochemistry and FISH assay are useful in differential diagnosis.

Through the looking glass and what you find there: making sense of comparative genomic hybridization and fluorescence in situ hybridization for melanoma diagnosis

Melanoma is the leading cause of death among cutaneous neoplasms. Best outcome relies on early detection and accurate pathologic diagnosis. For the great majority of melanocytic tumors, histopathologic examination can reliably distinguish nevi from melanomas. However, there is a subset of melanocytic tumors that cannot be definitively classified as benign or malignant using histopathological criteria alone. These tumors are usually diagnosed using terms that imply various degrees of uncertainty in regards to their malignant potential and create the possibility for over or undertreatment. For such tumors, additional ancillary tests would be beneficial in adjudicating a more definitive diagnosis. In recent years, DNA-based molecular ancillary tests, specifically comparative genomic hybridization and fluorescence in situ hybridization, have been developed to help guide the diagnosis of ambiguous melanocytic proliferations. This study will present an updated overview of these two major ancillary tests, which are currently being used in clinical practice to assist in the diagnosis of challenging melanocytic neoplasms.

Four-color fluorescence in-situ hybridization is useful to assist to distinguish early stage acral and cutaneous melanomas from dysplastic junctional or compound nevus

Background/objective

Acral and cutaneous melanomas are usually difficult to accurately diagnose in the early stage, owing to the similarity in clinical manifestations and morphology with those of dysplastic nevus (DN). In this study, we aimed to evaluate the diagnostic value of four-color fluorescence in-situ hybridization (FISH) probes specific to the RREB1,CCND1,and MYB genes, and centromere of chromosome 6, in distinguishing DN and melanoma.

Methods

Fifty one DN and 58 melanoma cases were collected and tested with four-color FISH. Histological features were reviewed and concordant morphologic diagnosis by three pathologists was considered the golden criterion.

Results

Fifty DN and 59 melanoma cases, with 37 melanomas in situ and 22 melanomas in Clark level 2, were confirmed finally; among them, 42 (71.2%) cases were acral. A comparison of clinicopathological features between the two entities showed that several features were considerably more frequently observed in the melanoma group, including more mitotic figures, stratum corneum pigmentation, lymphocyte infiltration, cell atypia, successive or pagetoid melanocyte growth pattern in the epidermis, larger tumor size, and older age at diagnosis. FISH was positive in 3 (6.0%) DN and 56 (94.9%) melanoma cases according to Gerami’s criteria. In distinguishing the two groups, the sensitivity of the four-color FISH was 94.9% and specificity was 94.0%.We found that CCND1 gain was the most sensitive, either in Gerami’s or Gaiser’s criteria. Further analysis showed that CCND1gain was more obvious in the acral group of melanoma.

Conclusions

We conclude that the four-color FISH test was highly sensitive and specific in distinguishing early-stage acral and cutaneous melanomas from dysplastic nevus in Chinese population, and the most sensitive criterion was the gain of CCND1.

Comparison of melanoma gene expression score with histopathology, fluorescence in situ hybridization, and SNP array for the classification of melanocytic neoplasms

While most melanomas can be distinguished from nevi by histopathology, the histology is ambiguous for some melanocytic tumors, contributing to diagnostic uncertainty. Therefore molecular assays, including FISH or SNP array, and more recently a gene expression test (myPath, Myriad Genetics) have been proposed to aid in the work-up of ambiguous tumors. Two hundred and sixty-eight prospectively submitted cases were gathered, with the goal of comparing the myPath assay to morphologic diagnosis in (1) morphologically unequivocal cases (198), and to morphologic diagnosis and FISH in (2) morphologically ambiguous cases (70). Melanoma FISH was performed using probes for 6p25, 6q23, 11q13, Cep6, 9p21, and Cep9 and scored according to established criteria. The myPath assay was scored by the manufacturer as benign, indeterminate, or malignant. In the unequivocal group, myPath assay showed 75% agreement with morphologic diagnosis, with 67% sensitivity and 81% specificity. In the ambiguous group, FISH and myPath showed 69% inter-test agreement. For these cases agreement with histopathologic interpretation was 84% for FISH and 74% for myPath. Sensitivity and specificity of FISH was 61 and 100%, 50 and 93% for myPath, respectively. Cases from both groups in which myPath was discordant with either morphologic diagnosis and/or FISH (81/268 cases), were submitted for evaluation by two experienced dermatopathologist and also by SNP-array. SNP-array results correlated better than FISH, which correlated better than myPath, with the morphologic interpretation. Our findings document that molecular diagnostics show good correlation with consensus diagnoses, but discordant results occur, and vary in level of correlation with consensus interpretations. Studies with long-term outcomes data within specific ambiguous lesion subsets are required to establish the accuracy of this test, as each molecular diagnostic technique has limitations based on both lack of clinical outcomes data in ambiguous melanocytic tumors and in terms of their sensitivity and specificity in melanocytic lesion subtypes.

Review of diagnostic, prognostic, and predictive biomarkers in melanoma

Melanoma is an aggressive cutaneous malignancy with rapidly rising incidence. Diagnosis of controversial melanocytic lesions, correct prognostication of patients, selection of appropriate adjuvant and systemic therapies, and prediction of response to a given therapy remain very real challenges. Despite these challenges, multiple high throughput, nucleic-acid based biomarkers have been developed that can be assayed from histologic tissue specimens. FISH, CGH, Decision-Dx, and other multi-marker assays have been combined to improve overall predictability. This review discusses some of the most promising nucleic acid based assays that can be obtained from tissue specimens to assist with diagnosis, prognostication, and prediction of treatment response.

Performance Testing of RREB1, MYB, and CCND1 Fluorescence In Situ Hybridization in Spindle-Cell and Desmoplastic Melanoma Argues for a Two-Step Test Algorithm

BACKGROUND

Diagnostic confirmation of spindle-cell melanoma (SM) or desmoplastic melanoma (DM) as a melanoma can be challenging. In conventional melanoma (CM), a recently established fluorescence in situ hybridization (FISH) assay for RREB1, MYB, CCND1 can be helpful. Here, we determined the presence of RREB1, MYB, and CCND1 abnormalities in an SM/DM/mixed cohort.

METHODS

We assembled 49 cases and performed 3 separate hybridizations for RREB1/MYB/CCND1. We assessed clinical utility in diagnostically challenging cases and performed a cost and turnaround time analysis.

RESULTS

With regard to the diagnosis of melanoma, the FISH assay is 76% sensitive (n = 31/41 true positives melanomas) and 88% specific (n = 1/8 false positive desmoplastic nevi). The prevalence of abnormalities in DM is lower (12/19 cases, 63%; P = .03) than in SM (15/18 cases, 83%; P = .27), mixed (4 of 4 cases), or the reported sensitivity in CM (345/411 cases, 84%). The implied genetic differences in DM result in a higher false negative rate in DM (37%). Despite these limitations, when restricted to diagnostically challenging cases (n = 23), the FISH assay and, in particular, RREB1 was able to confirm melanoma in 70% (n = 16/23). Individual probe sensitivities ( RREB1 > MYB > CCND1) and a cost and turnaround time analysis argues for a 2-step test algorithm that reduces the economic impact of FISH testing considerably (~55%; n = 69 vs 123 hybridizations).

CONCLUSION

We propose a step-by-step genetic testing algorithm to support the diagnosis of melanoma in the setting of SM/DM and show that FISH testing is useful in diagnostically challenging cases.

Novel computational method for predicting polytherapy switching strategies to overcome tumor heterogeneity and evolution

The success of targeted cancer therapy is limited by drug resistance that can result from tumor genetic heterogeneity. The current approach to address resistance typically involves initiating a new treatment after clinical/radiographic disease progression, ultimately resulting in futility in most patients. Towards a potential alternative solution, we developed a novel computational framework that uses human cancer profiling data to systematically identify dynamic, pre-emptive, and sometimes non-intuitive treatment strategies that can better control tumors in real-time. By studying lung adenocarcinoma clinical specimens and preclinical models, our computational analyses revealed that the best anti-cancer strategies addressed existing resistant subpopulations as they emerged dynamically during treatment. In some cases, the best computed treatment strategy used unconventional therapy switching while the bulk tumor was responding, a prediction we confirmed in vitro. The new framework presented here could guide the principled implementation of dynamic molecular monitoring and treatment strategies to improve cancer control.

The correlation of the standard 5 probe FISH assay with melanocytic tumors of uncertain malignant potential

BACKGROUND

FISH has recently emerged as a technique to better assess the malignant potential of histologically ambiguous melanocytic lesions. However, the usefulness of FISH has not been conclusively established. The purpose of this study was to further explore the diagnostic value of FISH in distinguishing the borderline melanocytic tumor (BMT) from melanoma.

METHOD

73 cases with BMT were analyzed retrospectively from a dermatopathology database between 2010-2015. FISH studies were conducted in each case using probes targeting 5 loci including CCND1 on 11q13, RREB1 on 6p25, MYB on 6q23, CDKN2A on 9p21, and CEP 6 control probe for chromosome 6.

RESULTS

The study was composed of 50 females and 23 males with an age range of 1-73 and a mean age of 35years. Of the 6 cases in the superficial atypical Spitz tumor (AST) category, 2 had indeterminate results due to polyploidy. In the conventional atypical Spitz tumor cases, FISH was positive in 3 of 15 cases. Of the 27 cases in the borderline nevoid tumor (BNM) category, 3 showed positive FISH and 3 were equivocal due to the possibility of polyploidy. 3 of 13 cases of the borderline tumor of deep penetrating nevus variant (B-DPN) were positive for FISH. Neither of the 2 pigmented epithelioid melanocytoma (PEM) cases had positive FISH result. Of the 4 cases in the superficial atypical dermoepidermal nevomelanocytic proliferation group, only 1 met the FISH diagnostic criteria for melanoma. None of the 6 borderline tumors with overlapping features met FISH criteria diagnostic of melanoma. Clinical follow up was available on 55 patients. None of the patients had recurrence nor died of the disease. Lymph node biopsy was performed on five patients without evidence of metastasis.

CONCLUSION

Despite the benefits of FISH, it is limited by the fact that melanomas are not genetically identical whereby certain genetic abnormalities are only seen in specific subtypes. Additionally, FISH only targets specific chromosomes resulting in limitations in sensitivity and specificity. Although FISH has proven to be highly sensitive and specific in distinguishing unequivocally benign from malignant lesions, in cases of histopathological ambiguity, these parameters cannot be assessed with great confidence because the histopathological diagnosis (gold standard) is not without uncertainty. The 4-probe set (excluding 9p21) consistently showed chromosomal aberrations throughout all groups, but only 10 of the 73 total cases (13%) met the diagnostic criteria for melanoma. Moreover, it would be wise to establish new cytogenetic reference values that incorporate these borderline lesions in an effort to better assess the possibility of malignant behavior and or define a cytogenetic profile supportive of its categorization as an indeterminate proliferation. Polyploidy is another inherent limitation, which leads to false positives due to the absolute signal counts incorrectly reflecting relative imbalances in the tumor genome.

Comparison between melanoma gene expression score and fluorescence in situ hybridization for the classification of melanocytic lesions

Melanoma accounts for most skin cancer-related deaths and has an increasing incidence. Accurate diagnosis and distinction from atypical nevi can be at times difficult using light microscopy alone. Fluorescence in situ hybridization (FISH) and melanoma gene expression score (myPath, Myriad Genetics) have emerged as ancillary tools to further aid in this differential diagnosis. Our aim in this study was to correlate FISH results, gene expression score, consensus histopathologic impression and clinical outcome on a series of 117 challenging melanocytic lesions collected from three separate institutions. The lesions were separated into two groups: 39 histopathologically unequivocal lesions (15 malignant, 24 benign) and 78 challenging lesions interpreted by expert consensus (27 favor malignant, 30 favor benign, and 21 ambiguous). Melanoma-FISH was performed using probes for 6p25, 11q13, 8q24, and 9p21/CEP9 and scored according to established criteria. Analysis by myPath gene expression score was performed and interpreted by the manufacturer as 'benign', 'indeterminate,' or 'malignant'. In the unequivocal group, melanoma-FISH and myPath score showed 97 and 83% agreement with the histopathologic diagnosis, respectively, with 93 and 62% sensitivity, 100 and 95% specificity, and 80% inter-test agreement. In the challenging group, FISH and the myPath score showed 70 and 64% agreement with the histopathologic interpretation, respectively, with 70% inter-test agreement and similar sensitivities and specificities. The inter-test agreement was 73% overall, excluding indeterminate results. Discordant test results occurred in 27/117 cases from both unequivocal and challenging groups. Melanoma-FISH and gene expression score are valuable ancillary tools, though both have limitations and return discordant results in a subset of cases. Follow-up studies with more extensive clinical outcome data are warranted to establish the accuracy of these tests for the classification of melanocytic lesions.

From melanocytes to melanomas

Melanomas on sun-exposed skin are heterogeneous tumours, which can be subtyped on the basis of their cumulative levels of exposure to ultraviolet (UV) radiation. A melanocytic neoplasm can also be staged by how far it has progressed, ranging from a benign neoplasm, such as a naevus, to a malignant neoplasm, such as a metastatic melanoma. Each subtype of melanoma can evolve through distinct evolutionary trajectories, passing through (or sometimes skipping over) various stages of transformation. This Review delineates several of the more common progression trajectories that occur in the patient setting and proposes models for tumour evolution that integrate genetic, histopathological, clinical and biological insights from the melanoma literature.

Methods of Melanoma Detection

Detection and removal of melanoma, before it has metastasized, dramatically improves prognosis and survival. The purpose of this chapter is to (1) summarize current methods of melanoma detection and (2) review state-of-the-art detection methods and technologies that have the potential to reduce melanoma mortality. Current strategies for the detection of melanoma range from population-based educational campaigns and screening to the use of algorithm-driven imaging technologies and performance of assays that identify markers of transformation. This chapter will begin by describing state-of-the-art methods for educating and increasing awareness of at-risk individuals and for performing comprehensive screening examinations. Standard and advanced photographic methods designed to improve reliability and reproducibility of the clinical examination will also be reviewed. Devices that magnify and/or enhance malignant features of individual melanocytic lesions (and algorithms that are available to interpret the results obtained from these devices) will be compared and contrasted. In vivo confocal microscopy and other cellular-level in vivo technologies will be compared to traditional tissue biopsy, and the role of a noninvasive "optical biopsy" in the clinical setting will be discussed. Finally, cellular and molecular methods that have been applied to the diagnosis of melanoma, such as comparative genomic hybridization (CGH), fluorescent in situ hybridization (FISH), and quantitative reverse transcriptase polymerase chain reaction (qRT-PCR), will be discussed.

Practical application of new technologies for melanoma diagnosis: Part II. Molecular approaches

The criterion standard for diagnosing cutaneous melanoma continues to be histologic examination. However, classifying some melanocytic lesions by conventional microscopy can be problematic if they exhibit some architectural or morphologic characteristics of both nevus and melanoma. Moreover, histologic appearance does not always predict biologic behavior. There is therefore a need and opportunity to develop new technologies that can facilitate the histologic diagnosis of melanoma and potentially help distinguish lesions with a lesser or greater risk of metastasis. In part II of this 2-part continuing medical education article, we will review the molecular technologies currently available for facilitating melanoma diagnosis, including comparative genomic hybridization, fluorescence in situ hybridization, and epidermal genetic retrieval. Our goal is to provide the clinician with an up to date understanding of these molecular approaches so that they can be applied to their management of challenging melanocytic lesions.

5-Hydroxymethylcytosine expression in metastatic melanoma versus nodal nevus in sentinel lymph node biopsies

Sentinel lymph node biopsies are conducted to stage patients with newly diagnosed melanomas that have histopathological attributes conferring defined levels of metastatic potential. Because benign nevic cells may also form 'deposits' in lymph nodes (nodal nevus), the pathological evaluation for metastatic melanoma within sentinel lymph nodes can be challenging. Twenty-eight sentinel lymph node biopsy cases containing either metastatic melanoma (N=18) or nodal nevi (N=10) were retrieved from the archives of the Brigham and Women's Hospital, Department of Pathology (2011-2014). In addition, two sentinel lymph node cases that were favored to represent metastatic disease but whose histopathological features were viewed as equivocal, with melanoma favored, were also included. Dual labeling for the melanocyte lineage marker, MART-1, and the epigenetic marker, 5-hydroxymethylcytosine, a functionally significant indicator that has been shown to distinguish benign nevi from melanoma, was performed on all cases using immunohistochemistry and/or direct immunofluorescence. All (18 of 18) metastatic melanoma cases showed complete loss of 5-hydroxymethylcytosine nuclear staining in MART-1-positive cells, and all (10 of 10) nodal nevus cases demonstrated 5-hydroxymethylcytosine nuclear staining in MART-1-positive cells. In addition, 5-hydroxymethylcytosine staining confirmed the favored diagnoses of metastatic melanoma in the two 'equivocal' cases. Thus, 5-hydroxymethylcytosine may be a useful adjunctive marker to distinguish between benign nodal nevi and metastatic melanoma during the evaluation of sentinel lymph node biopsies for metastatic melanoma.

Molecular markers in melanoma

The last few years have witnessed the dawn of the molecular era in melanoma treatment. With the advent of successful therapy targeting mutant BRAF, melanoma is leading the field of cancer research in the molecular approach to therapy of advanced disease. Attempting to keep pace with advances in therapy are advances in the molecular assessment of melanoma progression, facilitated by the availability of genome-wide approaches to interrogate the malignant phenotype. At the DNA level, this has included approaches such as comparative genomic hybridization. At the RNA level, this has consisted of gene expression profiling using various assay methodologies. In certain instances, markers identified using these platforms have been further examined and developed using fluorescence in situ hybridization and immunohistochemical analysis. In this article, we will review recent progress in the development of novel molecular markers for melanoma that are nearing clinical application. We will review developments in the molecular classification of melanoma, in the molecular diagnosis of melanoma, and in the molecular assessment of melanoma prognosis.

Diagnostic and prognostic biomarkers in melanoma

Melanoma is a lethal melanocytic neoplasm. Unfortunately, the histological diagnosis can be difficult at times. Distinguishing ambiguous melanocytic neoplasms that are benign nevi from those that represent true melanoma is important both for treatment and prognosis. Diagnostic biomarkers currently used to assist in the diagnosis of melanoma are usually specific only for melanocytic neoplasms and not necessarily for their ability to metastasize. Traditional prognostic biomarkers include depth of invasion and mitotic count. Newer diagnostic and prognostic biomarkers utilize immunohistochemical staining as well as ribonucleic acid, micro-ribonucleic acid, and deoxyribonucleic acid assays and fluorescence in situ hybridization. Improved diagnostic and prognostic biomarkers are of increasing importance in the treatment of melanoma with the development of newer and more targeted therapies. Herein, the authors review many of the common as well as newer diagnostic and prognostic biomarkers used in melanoma.

Cutaneous malignant melanoma: update on diagnostic and prognostic biomarkers

The incidence of cutaneous malignant melanoma has rapidly increased in recent years in all parts of the world, and melanoma is a leading cause of cancer death. As even relatively small melanomas may have metastatic potential, accurate assessment of progression is critical. Although diagnosis of cutaneous malignant melanoma is usually based on histopathologic criteria, these criteria may at times be inadequate in differentiating melanoma from certain types of benign nevi. As for prognosis, tumor (Breslow) thickness, mitotic rate, and ulceration have been considered the most important prognostic indicators among histopathologic criteria. However, there are cases of thin primary melanomas that have ultimately developed metastases despite complete excision. Given this, an accurate assessment of melanoma progression is critical, and development of molecular biomarkers that identify high-risk melanoma in its early phase is urgently needed. Large-scale genomic profiling has identified considerable heterogeneity in melanoma and suggests subgrouping of tumors by patterns of gene expression and mutation will ultimately be essential to accurate staging. This subgrouping in turn may allow for more targeted therapy. In this review, we aim to provide an update on the most promising new biomarkers that may help in the identification and prognostication of melanoma.

Chromosomal copy number analysis in melanoma diagnostics

The majority of melanocytic neoplasms can be correctly diagnosed using routine histopathologic analysis. However, a significant minority of tumors have ambiguous histopathologic attributes that overlap between melanocytic nevi and melanoma. Ancillary tests that assist in distinguishing potentially lethal melanomas from benign melanocytic nevi with atypical histopathologic features are available, but still need refining.Most melanomas have chromosomal copy number aberrations, frequently involving multiple chromosomes. With rare exceptions, such anomalies are not found in melanocytic nevi. This difference formed the basis to develop assays that can help distinguish melanoma from nevi by fluorescence in situ hybridization (FISH) and comparative genomic hybridization (CGH). FISH can detect chromosomal copy number changes of a limited number of loci within individual cells. By contrast, CGH assesses copy number across the entire genome, but typically is performed on bulk cell populations so that copy number changes in individual cells or subpopulations of cells can go undetected. Both FISH and CGH have been used to provide genomic information in histopathologically ambiguous melanocytic tumors that can assist pathologists make correct diagnoses.

What's new in prognostication of melanoma in the dermatopathology laboratory?

With the advent of genetic and epigenetic research, molecular techniques could someday be used to discriminate nevus from melanoma so that ambiguous melanocytic lesions could be more accurately classified or that prognostication could be improved in melanoma patients. That promised day might be closer than realized. The last 20 years of research in cytogenetic and genetic alterations in melanoma have culminated in defined chromosomal lesions discriminating benign from malignant melanocytic tumors. Exploiting these differences, fluorescence in situ hybridization (FISH) can reproducibly discriminate unequivocal melanomas from melanocytic nevi with high sensitivity and specificity. The discriminating power of FISH in melanocytic tumors with ambiguous histopathology is questionable, however, because there is no standard definition of "malignancy." Additional FISH studies on ambiguous cases are needed through international collaborations where large collections of such cases are shared and the "proof of malignancy" is established by adequate clinical follow-up. This contribution reviews the diagnostic utility of DNA-based FISH technology as it compares the diagnostic accuracy in melanocytic tumors with unambiguous vs ambiguous histopathology. The melanoma epigenome is further characterized through research into various activities of small interfering RNAs, such as microRNAs, providing the pathway for the application of microRNA-based strategies that could be the basis for future diagnostic biomarkers and molecular therapies in melanoma.

Molecular pathology of melanocytic tumors

Genetic and genomic analyses of melanocytic tumors have yielded new opportunities for improvements in diagnostic accuracy for the distinction of nevus from melanoma and better selection of patients affected by melanoma for targeted treatment. Since chromosomal copy number changes are commonly found in malignant melanoma, but rare in melanocytic nevi, cytogenetic assays have emerged as a promising ancillary study for the workup of melanocytic tumors with ambiguous light microscopic features. Comparative genomic hybridization (CGH) permits assessment of the full set of chromosomes, but requires a significant amount of lesional tissue, and may fail to detect aberrations in a minor subpopulation of tumor cells. Fluorescence in situ hybridization (FISH) is the cytogenetic assay of choice for limited amounts of tissue. FISH targets only specific chromosomes, with inherent limitations in test sensitivity and specificity. FISH analysis is also heavily dependent on individual experience. Molecular studies have identified distinct sets of mutations in melanoma and/or nevi. These mutations have become clinically relevant for targeted therapy of patients with advanced disease, especially for the treatment of patients with metastatic melanoma carrying the BRAF(V600) or KIT mutations. However, mutation analysis can on occasion also be used for diagnostic purposes.

Reticulin and NM23 staining in the interpretation of lymph nodal nevus rests

Melanocytic nevus rests in lymph nodes are a known diagnostic challenge, especially in patients with a history of melanoma. Reticulin and NM23 have been studied in this context. The pattern of reticulin staining in melanomas surrounds groups/nests of melanocytes but individual cells in benign nevi. NM23, a metastasis-suppressor gene, has an association with metastatic potential in melanomas and some carcinomas. Twenty-eight cases (14 cases of metastatic melanoma to lymph nodes and 14 cases of lymph node nevus rests, all confirmed with Melan-A staining) were stained with reticulin and NM23. The pattern of reticulin staining was reported as surrounding groups if staining was noted in approximately 5-10 melanocytes in greater than 50% of the lesion but was otherwise reported as surrounding individual melanocytes. Cytoplasmic staining was considered to represent reactivity for NM23. Reticulin staining around groups of melanocytes was identified in all 14 cases of metastatic melanoma. Regarding nodal nevus rest cases, 12 of 14 cases (86%) demonstrated staining around individual melanocytes, whereas in 2 cases, reticulin surrounded melanocytic groups. NM23 staining was equivocal in all cases. Reticulin staining reliably invests groups of melanocytes in cases of metastatic melanoma, whereas in nodal nevus rests, it predominantly surrounds individual melanocytes. NM23 demonstrated no discriminatory value in this analysis. In cases in which a collection of melanocytes is present within a lymph node, reticulin deposition around individual melanocytes supports a diagnosis of lymph nodal nevus rest.

Clinical characteristics and survival data of melanoma patients with nevus cell aggregates within sentinel lymph nodes

Histopathologic differentiation of nevus cell aggregates and metastatic melanoma in lymph nodes is challenging. Patients with melanoma who had undergone sentinel lymph node (SLN) biopsy were evaluated using univariate and multivariate analyses as well as Kaplan-Meier statistics. Of the 651 patients, 50 (7.7%) had a nodal nevus in the SLN. In the logistic regression model, primary melanoma on the lower extremities proved to be the strongest independent negative predictor of nodal nevi with an odds ratio of 0.11 (95% confidence interval, 0.034-0.36; P = .0002). Overall 5-year survival (P = .17) and 5-year disease-free survival (P = .45) of patients with nodal nevi did not significantly differ from that of patients with negative SLNs. The frequency and anatomic localization of nodal nevi observed in the present study are in line with previous studies. Our 5-year survival data clearly demonstrate that nevus cell aggregates in lymph nodes have to be considered a benign condition even though it occurs in patients with melanoma. This study provides an indirect proof of validity and accuracy of current histopathologic methods for differentiation between nodal nevi and melanoma metastasis.

Main clues in the pathologic diagnosis of melanoma: is molecular genetics helping?

Although conventional histopathologic examination is still the undisputable mainstay for the diagnosis of melanocytic skin neoplasms, application of molecular testing has experienced tremendous growth and will continue to expand in the future as the need for more specific diagnoses and new targeted therapies evolve. Ancillary molecular methods, including comparative genomic hybridization and fluorescence in situ hybridization, have the potential to provide important new information to challenging cases, and will help improve diagnostic accuracy, particularly in cases in which morphology is not conclusive. Pathologists are increasingly involved in the prospective genotyping of melanoma, which leads to patient stratification in light of the novel personalized therapeutic approaches in the advanced setting.

Homogeneous staining regions for cyclin D1, a marker of poor prognosis in malignant melanoma

Homogeneous staining regions (HSRs) have been previously shown to confer a worse prognosis in solid tumors and myelodysplastic syndromes. We previously reported a single case of melanoma with HSR for cyclin D1 and postulated that HSR for cyclin D1 is an independent poor prognostic indicator. Herein, we report 7 cases of melanoma with HSR for cyclin D1. The cases occurred in elderly men and women with an average age of 65 years. Three cases occurred in areas of intermittent sun exposure, 2 cases occurred in chronically sun-damaged areas, and 2 cases were acral. HSR correlated with aggressive histology. The average Breslow depth was 2.7 mm (range, 1-11 mm), the average mitotic index was 5.1 per square millimeter, and 5 of the 7 cases were ulcerated. Clinical follow-up was available for 6 of the 7 cases. Five of the 6 cases for which clinical follow-up was available metastasized, and 1 patient died of metastatic melanoma. Three cases with metastatic disease occurred in primary melanomas with lower Breslow depths, ranging from 1.0 to 1.4 mm. These additional cases of melanoma with an aggressive clinical course provide further evidence of the prognostic significance of HSR for cyclin D1 in melanoma. Larger cohort studies are needed to validate this observation.

Molecular diagnostic strategies: a role in the practice of dermatology

Molecular diagnostic strategies are gaining wider acceptance and use in dermatology and dermatopathology as more practitioners in this field develop an understanding of the principles and applications of genomic technologies. Molecular testing is facilitating more accurate diagnosis, staging, and prognostication, in addition to guiding the selection of appropriate treatment, monitoring of therapy, and identification of novel therapeutic targets, for a wide variety of skin diseases.

Cytogenetic and mutational analyses of melanocytic tumors

Analyses of genetic and genomic alterations of melanocytic tumors have not only led to a better understanding of the pathogenesis of melanocytic tumors but also created new opportunities for improvements in diagnostic accuracy in distinguishing nevus from melanoma, and more effective treatments for patients affected by melanoma. Cytogenetic tests have emerged as a promising ancillary method for the workup of diagnostically problematic melanocytic tumors with ambiguous light microscopic features. Mutation analysis not only is important in treatment decision making but also can be used for improved diagnostic accuracy, staging, and prognosis.

Differentiation of Malignant Melanoma From Benign Nevus Using a Novel Genomic Microarray With Low Specimen Requirements

Context.—Histologic examination of clinically suspicious melanocytic lesions is very sensitive and specific for the detection of malignant melanoma. Yet, the malignant potential of a small percentage of melanocytic lesions remains histologically uncertain. Molecular testing offers the potential to detect the genetic alterations that lead to malignant behavior without overt histologic evidence of malignancy.

Objective.—To differentiate benign melanocytic nevi from malignant melanoma and to predict the clinical course of melanocytic lesions with ambiguous histology using a novel genomic microarray.

Design.—We applied a newly developed single-nucleotide polymorphism genomic microarray to formalin-fixed, paraffin-embedded melanocytic lesions to differentiate benign nevi (n  =  23) from malignant melanoma (n  =  30) and to predict the clinical course of a set of histologically ambiguous melanocytic lesions (n  =  11).

Results.—For cases with unambiguous histology, there was excellent sensitivity and specificity for identifying malignant melanoma with this genomic microarray (89% sensitivity, 100% specificity). For cases with ambiguous histology, the performance of this genomic microarray was less impressive.

Conclusions.—Without microdissection and with quantities of DNA one-tenth what is required for more commonly used microarrays, this microarray can differentiate between malignant melanoma and benign melanocytic nevi. For histologically ambiguous lesions, longer clinical follow-up is needed to confidently determine the sensitivity and specificity of this microarray. Some of the previous technical hurdles to the clinical application of genomic microarray technology are being overcome, and the advantages over targeted fluorescence in situ hybridization assays currently in clinical use are becoming apparent.

Update on immunohistochemistry in melanocytic lesions

This article is an up-to-date overview of the potential uses and limitations of immunohistochemistry (IHC) in melanocytic lesions. The information is intended to assist dermatopathologists and dermatologists who read slides to appropriately use IHC in this setting. In addition, dermatologists who do not review microscopic slides will better understand the rationale of the pathologist when reading and interpreting the pathology report.

Application of fluorescence in situ hybridization as a diagnostic tool in melanocytic lesions, using paraffin wax-embedded tissues and imprint-cytology specimens

BACKGROUND

Accurate histopathological diagnosis of certain melanocytic skin lesions as benign or malignant can be notoriously difficult. Recently, four-colour fluorescence in situ hybridization (FISH) has emerged as an important tool for classifying these lesions.

AIM

To evaluate the sensitivity and specificity of a melanoma FISH probe kit for accurate diagnosis of melanocytic tumours, and to validate its use with imprint-cytology specimens from the cut surface of tumours.

METHODS

In total, 50 melanocytic skin lesions (31 malignant melanomas, 10 benign melanocytic naevi, and 9 histologically challenging benign melanocytic skin lesions) were evaluated. The samples comprise 47 tissue specimens embedded in paraffin wax, and three imprint-cytology specimens from the cut surface of melanomas. FISH was performed using four locus-specific identifier probes [Ras responsive element binding protein (RREB)1, myeloblastosis viral oncogene homologue (MYB), cyclin (CCN)D1 and centromere of chromosome (CEP)6], and results were compared with the clinical long-term follow-up and histopathological diagnosis data.

RESULTS

The melanoma FISH probe distinguished between naevi and melanomas with a sensitivity of 100% and a specificity of 94.1%. The most sensitive criterion was a gain in 6p25 (RREB1), seen in 100% of cases, followed by CEP6-related MYB loss (48.1%), CCND1 gain (37%) and MYB gain (22.2%). More than three-quarters (77.8%) of melanomas were positive for two or more criteria. Positive FISH results were also obtained for the imprint-cytology specimens.

CONCLUSIONS

FISH is a valuable diagnostic tool for differentiating between benign and malignant melanocytic lesions, providing a high degree of sensitivity and specificity. The probes displayed exceptional discriminative capacity in difficult or ambiguous lesions. To our knowledge, his is the first reported use of imprint-cytology specimens for FISH diagnosis.

The pathology of melanoma

Although melanoma represents only 10% of all skin cancer diagnoses, it accounts for at least 65% of all skin cancer-related deaths. The number of new cutaneous melanoma cases projected during 2010 was 68,000-a 23% increase from the 2004 prediction of 55,100 cases. In 2015, the lifetime risk of developing melanoma is estimated to increase to 1 in 50. As the incidence of melanoma continues to rise, now more than ever, clinicians and histopathologists must have familiarity with the various clinical and pathologic features of cutaneous melanoma.

Differentiation of melanoma and benign nevi by fluorescence in-situ hybridization

Malignant melanoma is sometimes difficult to distinguish from benign nevus, and ancillary confirmatory studies would be of value in selected cases. To accurately differentiate melanoma from benign nevus, we investigated the utility of chromosomal anomalies in skin biopsy specimens using multitargeted fluorescence in-situ hybridization (FISH). Skin biopsy specimens were retrospectively collected from 63 patients diagnosed with benign compound nevus (n=32) or malignant melanoma (n=31); each diagnosis was independently confirmed before study by a second dermatopathologist. Unstained tissue sections were hybridized for 30 min using fluorescence-labeled oligo-DNA probes for chromosomes 6, 7, 11, and 20. Fluorescent signals for each chromosome were enumerated in 30 cells per case. Numeric chromosomal anomalies were found in 0% (0 of 32) of normal epidermis, 6% (two of 32) of compound nevi, and 94% (29 of 31) of melanomas (nevus vs. melanoma, P<0.0001). The mean number of cells with chromosomal changes was 23 in melanoma specimens, significantly higher than that in compound nevi (P<0.0001). The most frequent chromosomal anomaly in melanoma was gain of chromosome 11, followed consecutively by gains of chromosomes 7, 20, and 6. Chromosomal anomalies detected by FISH had an overall sensitivity of 94% and specificity of 94% in the separation of nevus and melanoma. With the use of oligo-DNA probes, multitargeted FISH directed against chromosomes 6, 7, 11, and 20 is highly sensitive and specific for separation of nevus and melanoma. Unlike other traditional FISH probes, oligo-DNA probes required shorter hybridization time, allowing faster diagnostic evaluation.