Morphological analysis of nevoid melanoma: a study of 20 cases with a review of the literature

Prognosis of naevoid melanomas

INTRODUCTION

There appear to be several variants of naevoid melanoma suspected as having different outcomes, but follow-up studies have been few. We aimed to assess the prognosis of naevoid melanomas in a multi-centre study.

MATERIAL AND METHODS

From histopathology records we ascertained patients in the UK, Australia and Italy diagnosed with maturing naevoid melanoma (n = 65; 14; 7 respectively) and nodular/papillomatous naevoid melanoma (12; 6; 0), and patients with superficial spreading melanoma (SSM) from UK (73) and Australia (26). Melanoma deaths in UK patients were obtained from NHS Digital; in Australia, via the National Death Index and cancer registry; and in Italy, through clinical records. For maturing naevoid vs. SSM, we used Cox-proportional hazard regression models to compare survival adjusted for age, sex, tumour thickness, and ulceration, and additionally Fine-Gray regression analysis, to calculate sub-hazard ratios (SHR) in the UK cohort, accounting for competing causes of death.

RESULTS

Among UK patients, there was a non-significantly lower risk of melanoma death in maturing naevoid vs SSM, including after accounting for competing causes of death (SHR 0.40, 95% confidence interval (CI) 0.12-1.31), while among nodular/papillomatous naevoid melanoma patients, there were no melanoma deaths on follow-up. Two melanoma deaths occurred in Australian SSM patients, and none in maturing or nodular/papillomatous naevoid melanoma patients, after 5 years' minimum follow-up. None of the 7 Italian patients with maturing naevoid melanoma died of melanoma after nearly 12 years' average follow-up.

CONCLUSIONS

There was no significant difference in risk of death from melanomas with naevoid features, and SSM. Nodular/ papillomatous naevoid melanoma patients did not carry higher risk of death than SSM patients though the very few cases of the papillomatous naevoid variant limited our assessment.

Unusual conjunctival melanocytic proliferations. Report of five cases and review of the literature

Indeterminate melanocytic proliferations of the conjunctiva have both benign and malignant features that previously made these lesions nearly impossible to categorize in existing classification schemes. With the evolution of immunohistochemistry and molecular genetics, however, subclassifications have emerged that allow for a more tailored diagnosis and management. These conjunctival melanocytic proliferations include deep penetrating nevus, granular cell nevus, and nevoid melanoma. There remains a small subset of conjunctival melanocytic proliferations that defy precise characterization as nevi, primary acquired melanosis, or melanomas despite currently available ancillary diagnostic modalities and remain indeterminate. We highlight these unusual types of nevi and melanomas, with an update on their morphologic, immunohistochemical, and molecular genetic characteristics.

Artificial Intelligence Applied to a First Screening of Naevoid Melanoma: A New Use of Fast Random Forest Algorithm in Dermatopathology

Malignant melanoma (MM) is the "great mime" of dermatopathology, and it can present such rare variants that even the most experienced pathologist might miss or misdiagnose them. Naevoid melanoma (NM), which accounts for about 1% of all MM cases, is a constant challenge, and when it is not diagnosed in a timely manner, it can even lead to death. In recent years, artificial intelligence has revolutionised much of what has been achieved in the biomedical field, and what once seemed distant is now almost incorporated into the diagnostic therapeutic flow chart. In this paper, we present the results of a machine learning approach that applies a fast random forest (FRF) algorithm to a cohort of naevoid melanomas in an attempt to understand if and how this approach could be incorporated into the business process modelling and notation (BPMN) approach. The FRF algorithm provides an innovative approach to formulating a clinical protocol oriented toward reducing the risk of NM misdiagnosis. The work provides the methodology to integrate FRF into a mapped clinical process.

Mitotically Active Nevus and Nevoid Melanoma: A Clinicopathological and Molecular Study

ABSTRACT

The distinction between nevoid melanoma and a mitotically active nevus can be challenging at the microscopic level. In this study, we performed cytogenetic testing on a cohort of 25 mitotically active melanocytic proliferations resembling common melanocytic nevus from 25 patients. Based on cytogenetic findings, the lesions were classified as "nevoid melanoma" (n = 13) or "mitotically active nevus" (n = 12). Subsequently, we compared the clinicopathological features between these 2 groups. Nevoid melanomas occurred in older patients (P = 0.007); however, there were no significant differences in gender, size, or anatomical distribution between the 2 groups. Histologically, deep/marginal mitoses (P = 0.006), lack of maturation with depth (P = 0.036), and pseudo-maturation (P = 0.006) were significantly more common in nevoid melanomas. Immunohistochemically, complete loss of p16 was an important divisive feature (P = 0.0004), seen in 70% of nevoid melanomas, and highly correlated with loss of CDKN2A gene (chromosome 9p21). Our findings suggest that such reproducible immunomorphological differences can be of value in distinguishing nevoid melanoma from mitotically active nevus. Nevoid melanomas demonstrated a spectrum of chromosomal aberrations similar to those seen in common subtypes of melanoma, which can serve as a powerful adjunct diagnostic tool in morphologically challenging lesions.

Common traps/pitfalls and emergency diagnosis in dermatopathology

Although all diagnoses in dermatopathology are important, three main groups may be highlighted. One group includes diagnoses that need to be communicated to the treating physician as soon as possible (this review includes infectious process while erythema multiforme and related diseases are discussed elsewhere in this series). A second group has diagnoses significant for their association with syndromes or internal malignancies. And a third group includes malignant lesions that can be confused histologically with benign ones or lesions that have an aggressive behavior unexpected for their apparently low-grade histology. This manuscript describes some of these important diseases and the method we use to reach the diagnosis, and as such it may be considered to be a "survival" guide for the dermatopathologist.

"Puffy shirt appearance": Cell crowding at low magnification may represent nevoid melanoma

BACKGROUND

Melanoma, particularly nevoid melanoma, can masquerade as benign. Helpful differentiating features include nuclear pleomorphism, atypia, prominent nucleoli, absent maturation, and increased mitotic figures. These can be subtle and easily missed unless carefully sought. Thus, the "puffy shirt appearance" concept was born from a Seinfeld episode in which the namesake character unintentionally agreed to wear a pirate-like puffy shirt. Consequently, he found himself out of place, sporting an outfit with "too much shirt in too little space". Similarly, at low-power, nevoid melanoma appears to have "too many cells in too little space". This is more pronounced and easier to appreciate when there is an associated nevus, where crowded, subtly malignant melanocytes stand out from the evenly distributed, more spaced out benign melanocytes.

METHODS

Twelve practicing dermatopathologists familiar with the puffy shirt concept in the context of melanoma were surveyed.

RESULTS

Hundred percent of participants found it most helpful as a triaging tool, prompting additional work up including higher magnification evaluation, additional levels, consultation, and/or immunohistochemistry.

CONCLUSIONS

The crowded cells in the "puffy shirt appearance" catch the eye and should provoke a more thorough inspection of the lesion. This sign is not pathognomonic for melanoma, but prompts more careful evaluation and helps prevent misdiagnosis.

Pathological review of primary cutaneous malignant melanoma by a specialist skin cancer multidisciplinary team improves patient care in the UK

AIMS

The National Institute for Health and Care Excellence advocated the development of specialist skin cancer multidisciplinary teams (SSMDTs) for the management of higher risk invasive skin cancers in the UK. The interobserver variability in the histopathological assessment of primary cutaneous malignant melanoma (PCMM) is well recognised.

METHODS

We evaluated the discordance rates in the assessment of the histopathological criteria of PCMM based on the eighth American Joint Committee on Cancer (AJCC) melanoma staging system and subsequent change in prognosis and management following pathology review by an SSMDT.

RESULTS

353 cases of PCMM were referred to our SSMDT between April 2015 and May 2016. Cases in which there was a discrepancy in one or more histological parameters following expert review were collected retrospectively. Of 341 eligible cases, there were 94 (27.6%) in which there was an alteration in any parameter. There was interobserver agreement in final diagnosis in 96.8%, Breslow thickness in 86.8%, ulceration in 98.2%, microsatellites in 98.5%, tumour mitotic rate in 88.9%, histological subtype in 92.4%, growth phase in 98.5%, angiolymphatic invasion in 97.7%, perineural invasion in 98.8%, regression in 95.3% and tumour-infiltrating lymphocytes in 95.0%. A corresponding change in AJCC stage occurred in 23 cases (6.7%), with a resulting change in clinical management in 10 cases (2.9%).

CONCLUSIONS

Disagreements in the pathological assessment of PCMM can have significant clinical implications for a small number of patients. Our findings highlight the value of the SSMDT for high-quality care of patients with melanoma in the UK.

Unusual Clinical Presentations of Malignant Melanoma: A Review of Clinical and Histologic Features with Special Emphasis on Dermatoscopic Findings

This review presents the main challenges encountered when diagnosing unusual variants of malignant melanoma with the aim of raising awareness to allow application of the most appropriate treatment strategies. Although these melanomas are often rare, their misdiagnosis potentially jeopardizes patients' health and survival, and has medicolegal implications. The clinical and histologic presentations of melanoma vary greatly, and assessment of uncommon melanomas can be difficult for practitioners because of their scarcity and resemblance to other dermatologic entities. The most problematic melanoma types are desmoplastic melanoma, polypoid melanoma, primary dermal melanoma, verrucous malignant melanoma, pigmented epithelioid melanocytoma, mucosal melanoma, follicular melanoma and melanoma with non-melanocytic differentiation. The two most difficult-to-diagnose subtypes of melanoma are the nevoid and the amelanotic melanomas. Some specific attributes of these variants can be more easily recognized with digital dermatoscopy, facilitating early detection and possibly avoiding invasive procedures. Key cases with the most notable clinical, dermatoscopic, and histopathologic features are presented, highlighting the practical issues of making an accurate diagnosis and choosing the best therapy.

Clinicopathologically problematic melanocytic tumors: a case-based review

Background

In spite of recent advances in the histopathological and molecular diagnosis of melanocytic neoplasms, a certain proportion of these lesions remain a daunting challenge for both the clinician and the pathologist.

Objectives

To emphasize the importance of close collaboration between clinicians and pathologists in case of problematic melanocytic lesions.

Patients

We report and discuss 5 problematic scenarios of melanocytic lesions, including tumoral melanosis, nevoid melanoma, lentiginous melanoma, spitzoid melanoma and BAPoma that may pose diagnostic difficulties in our practice.

Conclusions

Clinico-dermoscopic-pathological correlation, with incorporation of all the available data, in problematic melanocytic skin neoplasms is of paramount importance for accurate diagnosis.

A Practical Approach to the Diagnosis of Melanocytic Lesions

CONTEXT.—

Melanocytic lesions are common in routine surgical pathology. Although the majority of these lesions can be confidently diagnosed using well-established morphologic criteria, there is a significant subset of lesions that can be diagnostically difficult. These can be a source of anxiety for patients, clinicians, and pathologists, and the potential consequences of a missed diagnosis of melanoma are serious.

OBJECTIVE.—

To provide a practical approach to the diagnosis of melanocytic lesions, including classic problem areas as well as suggestions for common challenges and appropriate incorporation of ancillary molecular techniques.

DATA SOURCES.—

Literature search using PubMed and Google Scholar, incorporating numerous search terms relevant to the particular section, combined with contemporaneous texts and lessons from personal experience.

CONCLUSIONS.—

Although a subset of melanocytic lesions can be diagnostically challenging, the combination of a methodical approach to histologic assessment, knowledge of potential diagnostic pitfalls, opinions from trusted colleagues, and judicious use of ancillary techniques can help the pathologist navigate this difficult area.

Comprehensive histopathological comparison of epidermotropic/dermal metastatic melanoma and primary nodular melanoma

AIMS

Metastatic melanoma involving the epidermis and/or upper dermis may show significant histological overlap with primary cutaneous melanoma, especially the nodular subtype. Proper histopathological classification is crucial to appropriate staging and management, but is often challenging. The aim of this study was to identify helpful histopathological features for differentiating epidermotropic/dermal metastatic melanoma (EDMM) and primary nodular melanoma (PNM).

METHODS AND RESULTS

A cohort of EDMMs (n = 74) and PNMs (n = 75) was retrospectively reviewed for various histopathological features, and the data were compared between groups by the use of univariate analysis. Features significantly associated with EDMM included a tumour size of <2 mm, an absence of tumour-infiltrating lymphocytes and plasma cells, monomorphism, and involvement of adnexal epithelium. Features associated with PNM included a polypoid (exophytic) configuration, prominent tumour-infiltrating plasma cells (TIPs), a tumour size of >10 mm, ulceration, epidermal collarettes, a higher mitotic rate, necrosis, multiple phenotypes, significant pleomorphism, and lichenoid inflammation. In multivariate analysis, a logistic regression model including large tumour size, ulceration, prominent TIPs, lichenoid inflammation and epidermal collarettes was highly predictive of PNM. Six (8%) EDMMs from three patients showed an 'epidermal-only' or 'epidermal-predominant' pattern closely simulating in-situ or microinvasive melanoma. Two of these cases were tested by fluorescence in-situ hybridisation, which confirmed clonal relationships with their corresponding primary melanomas.

CONCLUSIONS

This is the first comprehensive histopathological comparison of EDMM and PNM. Recognition of the above histopathological associations should aid in the correct classification and staging of cutaneous melanoma. Epidermotropic metastatic melanomas may occasionally show an epidermal-only/epidermal-predominant pattern; accurate diagnosis requires prudent clinical correlation and, when necessary, ancillary molecular tests.

New insights into naevoid melanomas: a clinicopathological reassessment

AIMS

Because the term 'naevoid melanoma' has variable clinical and pathological interpretations, we aimed to clarify the features of melanomas referred to as naevoid.

METHODS AND RESULTS

A review was undertaken of 102 melanomas diagnosed histopathologically as naevoid melanomas and ascertained by European Organization for Research and Treatment of Cancer Melanoma Group Subcommittee pathologists from their records. We found these could be classified morphologically into three groups. Thirteen melanomas were overlying genuine naevi and were therefore excluded. Of the 89 melanomas considered to be naevoid, 11 presented clinically as exophytic papillomatous nodules with little junctional component and composed of small atypical cells showing numerous mitoses and no change with depth; we termed these 'papillomatous naevoid' melanomas. The other 78 were flat or only slightly raised, and had a superficial spreading melanoma-like component with maturation to a small cell, but still an atypical, dermal component; we termed these 'maturing naevoid' melanomas. We showed that papillomatous and maturing naevoid melanomas also have differing immunochemical profiles. Preliminary clinical follow-up suggested different outcomes for these two naevoid melanoma types.

CONCLUSIONS

Melanomas that have been classified as naevoid melanomas comprise two types with distinct clinical, histopathological and immunohistochemical features that may also be prognostically significant.

Molecular techniques for predicting behaviour in melanocytic neoplasms

Molecular tools are rapidly emerging as novel tools for clinicians caring for cancer patients. Roles for these assays in melanocytic neoplasms include diagnosis for histologically ambiguous tumors, prognosis for conventional melanoma, and theragnosis for advanced disease. The introduction of these molecular strategies is timely, as different therapeutic options are rapidly developing to treat melanoma. With the development of new and effective therapeutic options, it is more critical than ever to improve the discrimination between patients with aggressive disease and those with more indolent tumours. In this review, we will evaluate the traditional staging of melanoma and what are the likely greatest opportunities for improvement with molecular strategies. We will explore a number of molecular assays that are now commercially available for the assessment of melanocytic neoplasms, which include techniques such as fluorescence in situ hybridisation, comparative genomic hybridisation, mRNA expression profiling and next generation sequencing, and discuss the optimal utilisation of each of these assays.

[Histological spectrum of malignant melanoma]

The diagnosis of melanocytic tumors is one of the most problematic areas in dermatology and diagnostic pathology. Melanoma is a malignant melanocytic tumor and the risk for metastasis and associated mortality is mainly dependent on tumor thickness and depth of invasion. Early recognition and correct diagnosis is therefore important for successful and effective treatment. The correct diagnosis of melanoma is, however, challenging due to the wide morphological spectrum. Historically, the disease was subdivided into superficial spreading, nodular, lentigo maligna and acral lentiginous melanoma but many more subtypes have subsequently been added. Some of these melanoma variants also show differences relating to the genetic background, clinical presentation, prognosis and treatment and may be associated with a specific differential diagnosis. In this article four of these melanoma variants, desmoplastic melanoma, nevoid melanoma, malignant blue nevus and pigment synthesizing melanoma will be discussed in more detail.

Morphologic clues and utility of fluorescence in situ hybridization for the diagnosis of nevoid melanoma

BACKGROUND

Nevoid melanomas include melanomas with a low power silhouette similar to melanocytic nevi. However, at higher power magnification, nevoid melanoma may have severe nuclear atypia and dermal mitoses.

METHODS

We performed a clinical, pathological and molecular study on a series of 58 examples of nevoid melanoma, excluding cases with spitzoid morphology.

RESULTS

We identified distinct morphologic patterns: 'classic' nevoid melanoma, superficial spreading melanomas with nevoid invasive melanoma, lentigo maligna with nevoid invasive melanoma and deep penetrating nevus-like nevoid melanoma. Fluorescence in situ hybridization (FISH) was positive in 74% of cases. Copy number gains in 8q24 were common in amelanotic nevoid melanoma. The median follow-up was 28 months (range 140). At last follow-up, 37 patients had no evidence of disease, 3 were alive with metastases and 6 died from metastatic melanoma. Of these six patients who died, four had a sentinel lymph node biopsy (SLNB) performed, which was negative in all four.

CONCLUSIONS

We describe distinct clues to the diagnosis of nevoid melanoma including occult intraepidermal atypia, and expansile nesting resulting in asymmetric silhouette or dermal papillae expansion. We also describe that nevoid melanoma have infrequent SLNB involvement in aggressive cases, and have frequent 8q24 gains rather than 9p21 deletions. Our results suggest that nevoid melanoma are distinct from spitzoid melanomas and should be distinguished.

Morphological features of naevoid melanoma: results of a multicentre study of the International Dermoscopy Society

BACKGROUND

Naevoid melanoma (NeM), a rare variant of melanoma, can be difficult to detect as its clinical and histopathological morphology can simulate a naevus.

OBJECTIVES

To describe the clinical and dermoscopic features associated with NeM.

METHODS

Lesions with a histopathological diagnosis of NeM were collected via an e-mail request sent to all members of the International Dermoscopy Society. All lesions were histopathologically reviewed and only lesions fulfilling a set of predefined histopathological criteria were included in the study and analysed for their clinical and dermoscopic features.

RESULTS

Twenty-seven of 58 cases (47%) fulfilled the predefined histopathological criteria for NeM and were included in the study. Clinically, 16 of the 27 NeMs presented as a nodular lesion (59%), eight (30%) as plaque type and three (11%) as papular. Analysis of the global dermoscopic pattern identified three types of NeM. The first were naevus-like tumours (n = 13, 48%), typified by a papillomatous surface resembling a dermal naevus. In these lesions local dermoscopic features included irregular dots/globules (46%), multiple milia-like cysts (38%) and atypical vascular structures (46%). The second type were amelanotic tumours (n = 8, 30%), typified by an atypical vascular pattern (75%). The third type consisted of tumours displaying a multicomponent pattern (n = 4, 15%), characterized by classical local melanoma-specific criteria. Two lesions (7%) were classified as mixed-pattern tumours as they did not manifest any of the aforementioned patterns.

CONCLUSIONS

While NeMs may be clinically difficult to differentiate from naevi, any papillomatous lesion displaying dermoscopically atypical vessels and/or irregular dots/globules should prompt consideration for the possible diagnosis of NeM.

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.

Mitotic activity within dermal melanocytes of benign melanocytic nevi: a study of 100 cases with clinical follow-up

It is generally accepted that otherwise benign intradermal or compound melanocytic nevi may show mitotic activity within dermal melanocytes. However, it is not known whether there is any clinical significance to this finding. Our objective is to analyze and describe the clinicopathologic features of benign nevi with mitotic activity (NMA). To do this, we collected 100 consecutive NMA during the usual course of business in our private dermatopathology practice. These cases were seen between the years 2000 and 2008. We then collected clinical and pathologic data on these cases and compared the findings with 100 control nevi without mitotic activity (CN). We compared these nevi with regard to demographic features, clinical history provided by clinician, and clinical follow-up, as well as anatomic site and season of biopsy, type of nevus, and selected histologic features (ie, trauma). We also estimate the incidence of NMA and describe the amount and location of mitotic figures within the NMA. Our results indicate that the incidence of NMA is 0.91%. Most (80) NMA revealed only one mitotic figure, whereas some (20) NMA revealed more than one mitotic figure. Most NMA (89) showed mitotic activity in the upper portion of the nevus, whereas some (11) showed mitotic activity in the lower portion of the nevus. NMA patients were of younger age than the CN patients (P = 0.0019). Compared with CN, the NMA were more likely to be from the extremities (P = 0.0113) or head and neck (P = 0.0237) and less likely to be from the trunk (P < 0.001). The NMA were also more likely to show histologic features suggesting a congenital onset (P < 0.001) and were more likely to be Spitz nevi (P = 0.0185). Compared with the CN, the NMA were more often reexcised (P = 0.0073) and more often, there was residual nevus in the reexcision specimen (P = 0.13), although the latter finding was not statistically significant. Anecdotally, 2 of our NMA were identified adjacent to invasive melanomas; however, on clinical follow-up, we were unable to detect any increased incidence of melanoma.

Evolving concepts in melanoma classification and their relevance to multidisciplinary melanoma patient care

In the initial period after melanoma was recognised as a disease entity in the early 1800's, it was subclassified on the basis of its presumed origin (from a precursor naevus, from a melanocytic precursor lesion acquired during adult life or in previously blemish-fee skin). In 1967 the eminent American pathologist, Dr Wallace Clark, proposed a histogenetic classification for melanoma in which the disease was subdivided predominantly on the basis of histopathological features of the intra-epidermal component of the tumour adjacent to any dermal invasive component. The subtypes were superficial spreading melanoma (SSM), lentigo maligna melanoma (LMM) and nodular melanoma (NM). Whilst additional entities, including acral lentiginous melanoma, mucosal melanoma, desmoplastic melanoma and naevoid melanoma have since been recognised, SSM, LMM and NM remain in the latest (2006) version of the WHO melanoma classification. Clark's histogenetic classification has been criticised because the criteria upon which it is based include clinical features (such as the site of the melanoma) and non-tumourous histopathological features (such as the character of the associated epidermis and the degree of solar elastosis) and also because of overlap in defining features, lack of an independent association with patient outcome and minimal relevance as a determinant of clinical management. However, such criticisms fail to acknowledge its importance in highlighting the myriad of clinical and histological guises of melanoma, which if not recognized by clinicians and pathologists will inevitably lead to a delay in diagnosis and a concomitant adverse clinical outcome. Recently, mutually exclusive oncogenic mutations in melanomas involving NRAS (15-20%), BRAF (50%), CKIT (2%), and GNAQ/GNA11 (50% of uveal melanomas) have been identified. This might herald the beginning of a new molecular classification of melanoma in which the biologically distinct subsets share a common oncogenic mechanism, behave clinically in a similar fashion and require similar clinical management. These discoveries are already being successfully exploited as therapeutic targets in clinical trials of metastatic melanoma patients with promising activity. Whilst there remains much to be discovered in this rapidly evolving field, there is already great optimism that more rational and effective therapies for melanoma patients will soon be widely available.

Spindle cell melanocytic lesions--part I: an approach to compound naevoidal pattern lesions with spindle cell morphology and Spitzoid pattern lesions

Melanocytic lesions show great morphological diversity in their architecture and the cytomorphological appearance of their composite cells. Whereas functional melanocytes reveal a dendritic cytomorphology and territorial isolation, lesional naevomelanocytes and melanoma cells typically show epithelioid, spindled or mixed cytomorphologies and a range of architectural arrangements. Spindling is common to melanocytic lesions, and may be either a characteristic feature or a divergent appearance. The presence of spindle cells may mask the melanocytic nature of a lesion, and is often disconcerting, either because of its infrequent appearance in a particular lesion or its interpretation as a dedifferentiated phenotype. Spindle cell melanocytic lesions follow the full spectrum of potential biological outcomes, and difficulty may be experienced judging the nature of a lesion because of a lack of consistently reliable features to predict biological behaviour. Over time, recognition of numerous histomorphological features that may portend a more aggressive lesion have been identified. However, the translation of these features into a diagnostic entity requires a gestalt approach. Although most spindle cell melanocytic lesions can reliably be resolved with this standard approach, problem areas do exist and cause no end of grief to the surgical pathologist or dermatopathologist. In this review, the authors present their algorithmic approach to spindle cell melanocytic lesions and discuss each entity in turn, in order to (1) model a systematic approach to such lesions, and (2) provide familiarity with those melanocytic lesions that either typically or occasionally display a spindled cytomorphology.

Clues to the diagnosis of atypical melanocytic lesions

This review, based on a lecture given at the 2009 Update in Dermatopathology meeting held at the Institute of Dermatology (London, UK), discusses the problem of misdiagnosing atypical benign melanocytic lesions as melanoma and the alternative problem of interpreting naevoid melanoma as a banal naevus. Consequences are considered. Brief consideration of a range of other melanoma variants that may be a source of diagnostic difficulty is also included.

Fluorescence in situ hybridization for distinguishing nevoid melanomas from mitotically active nevi

Nevoid melanoma may resemble benign compound or intradermal nevi by their silhouette and profile on low power. Higher power usually reveals nuclear atypia, confluence of cells, incomplete maturation and dermal mitotic activity. However, to some extent all of these features maybe seen in benign compound or intradermal nevi and no single criteria can be used to differentiate nevoid melanoma from a benign nevus. The distinction can be particularly problematic in nevi that show mitotic activity and we have noted a recent trend in diagnosis of melanocytic neoplasms with dermal mitosis as nevoid melanoma despite the presence of normal maturation in the dermis and lack of significant nuclear atypia. Therefore in this study we evaluated 10 nevoid melanomas, 4 of which resulted in metastasis and 10 mitotically active nevi with fluorescence in situ hybridization targeting key chromosomal loci previously shown to effectively discriminate been malignant and benign melanocytic neoplasms. All 10 nevoid melanomas showed copy number abnormalities by fluorescence in situ hybridization in either chromosome 6 or 11 while none of the 10 mitotically active nevi did. The results demonstrate that fluorescence in situ hybridization targeting key chromosomal loci on chromosomes 6 and 11 can be effective in discriminating nevoid melanomas from mitotically active nevi. Additionally, our study presents further evidence that dermal mitoses alone without other diagnostic features such as nuclear atypia and lack of maturation does not constitute sufficient evidence alone for a diagnosis of melanoma.

Carcinoid-like pattern in melanoma: report of 4 cases

Cutaneous melanoma can produce a wide variety of unusual morphological appearances, sometimes mimicking other tumors. We report on 4 cases of melanoma with carcinoid-like features, namely, arrangement of neoplastic cells in trabecules, ribbons, pseudorosettes, rosettes, and/or small round islands. A total of 10 biopsies from 4 patients were available for a histopathological study comprising congenital nevus, a nodule that had developed in this nevus and its persistence/recurrence, 3 primary cutaneous lesions, 3 metastases, and a recurrent/persistent lesion. In 7 of these 10 lesions, the most characteristic finding was a distinctive arrangement of the neoplastic cells as trabecules, ribbons, pseudorosettes, rosettes, or small round insular islands, thus closely resembling cell arrangement in carcinoids of various organs. All these tumors were positive for melanocytic markers. No neuroendocrine differentiation was demonstrated immunohistochemically. We conclude that the carcinoid-like pattern in melanoma, namely, the pattern in which neoplastic cells are arranged in trabecules, ribbons, cords, rosettes, pseudorosettes, and small round insular nests resembling those in carcinoids, is a distinctive pattern, which may rarely occur in primary cutaneous melanoma, its recurrence or metastasis, or in a melanoma associated with a large congenital nevus. This morphological type of melanoma may produce a serious diagnostic pitfall, but despite a confusing microscopic appearance, these tumors seem to demonstrate a conventional immunohistochemical profile.

Nevoid Melanoma

This article discusses the key features of nevoid melanoma. Gross features, microscopic features, immunohistochemistry, differential diagnosis, diagnosis, prognosis, and treatment are also discussed.

The classification of cutaneous melanoma

Forty years ago, a clinical and histological classification scheme and prognostic factors were described for cutaneous melanoma. This scheme included the subtypes superficial spreading, nodular and lentigo maligna, and prognostic factors including tumor thickness, ulceration, and mitotic activity. There have been some tweaks to the classification scheme, but these basic findings form the foundation for melanoma diagnosis and staging today. Currently, no molecular marker or target has proved reliably useful in the staging or treatment of melanoma. Measurement with a simple ruler serves as the basis for the staging of primary cutaneous melanoma, while the recognition of primary tumor mitotic activity and ulceration also remain significant factors. Recently, mutational analysis has revealed a correlation of activating mutations with the morphological descriptors from decades ago. Future classification schemes may have more power in predicting response to therapy by integrating specific genomic and intra-tumoral expression profiles with histologic findings.

Melanoma prognostic factors found in the dermatopathology report

Significant prognostic information is available in a routine melanoma dermatopathology report. Features that are enumerated in the pathology report and that portend a potentially poorer prognosis are older age, site (acral, head, neck), male sex, increasing Breslow tumor thickness, increasing Clark's level, ulceration, increasing number of mitoses, vertical growth phase, regression, absence of a host inflammatory response, increased tumor vascularity, angiotropism, vascular invasion, neurotropism, marked atypia, and satellite metastasis.

Comparison of pHH3, Ki-67, and survivin immunoreactivity in benign and malignant melanocytic lesions

Differentiating malignant melanoma from benign melanocytic lesions can be challenging. We undertook this study to evaluate the use of the immunohistochemical mitosis marker phospho-Histone H3 (pHH3) and the proliferation markers Ki-67 and survivin in separating malignant melanoma from benign nevi. Sixty-six melanocytic lesions (18 malignant melanomas, 8 Spitz nevi, 20 dysplastic nevi, and 20 compound nevi) were stained with antibodies to pHH3, Ki-67, and survivin. No pHH3 expression was detected in the dermis of compound and dysplastic nevi. Rare mitoses were observed in the superficial dermis in 3 of 8 Spitz nevi (37%). Staining for pHH3 was higher in malignant melanomas [average 25 per 10 high-power field (HPF), range 2-75 per 10 HPF] than in Spitz nevi (average 0.5 per 10 HPF, range 0-2 per 10 HPF) and was heterogeneously distributed in the malignant melanomas compared with a superficial dermal location in Spitz nevi. There was no cytoplasmic staining for survivin in any of the 66 melanocytic lesions and no nuclear staining in any of the benign ones. Survivin nuclear staining was present in 12 of 18 cases of malignant melanoma (67%) with an average index of 7% (range 0%-15%). In benign melanocytic lesions, the Ki-67 index was less than 5% (range 0%-4%) and staining was present close to the dermo-epidermal junction compared with an average index of 27% in melanomas (range 5%-50%) and a generally heterogeneous pattern of staining throughout the dermis. pHH3 and Ki-67 can be useful adjuncts to histopathology to separate malignant melanoma from benign nevi. pHH3 is especially useful to highlight mitoses and to rapidly assess the mitotic activity in melanocytic lesions.

Melanocytic aggregation in the skin: diagnostic clues from lentigines to melanoma

Pigmented skin lesions are among the most common skin lesions. Among them, melanocytic proliferations are morphologically diverse and their behavior may be difficult to discern with certainty. Researchers must be able to distinguish melanocytic from nonmelanocytic pigmented skin lesions and, in particular, benign from malignant lesions. The majority of these lesions can be diagnosed with ease; however, a minority of cases is difficult and have potential for error. The authors have systematically analyzed the clinical and dermoscopic features of melanocytic skin lesions, so as to increase in vivo diagnostic accuracy.

Unusual histologic and clinical variants of melanoma: Implications for therapy

Unusual histologic variants of melanoma may be problematic to the histopathologist. Several of these variants are sufficiently rare that their biologic behavior remains obscure. As identification of some of these melanoma subtypes has specific implications for the therapeutic approach, and as some may mimic other forms of epithelial or mesenchymal neoplasia, their recognition is key to patient management.

Melanocytic nevi simulant of melanoma with medicolegal relevance

A group of melanocytic benign nevi are prone to be misdiagnosed as nodular or superficial spreading melanoma. This review illustrates the most frequent forms of these nevi in direct comparison with their malignant morphologic counterparts. The nevi are: hyper-cellular form of common nevus to be distinguished from nevoid melanoma, Spitz nevus (vs spitzoid melanoma), Reed nevus (vs melanoma with features of Reed nevus), cellular atypical blue nevus (vs melanoma on blue nevus), acral nevus (vs acral melanoma), Clark dysplastic nevus (vs superficial spreading melanoma), desmoplastic nevi (vs desmoplastic melanoma), benign proliferative nodules in congenital nevi (vs melanoma on congenital nevi), epithelioid blue nevus (vs animal type melanoma) and regressed nevus (vs regressed melanoma). For each single 'pair' of morphological look-alikes, a specific set of morphological, immunohistochemical and genetic criteria is provided.

Selected Diagnostic Problems in Neoplastic Dermatopathology

Context.—Selected cutaneous neoplasms share features with benign counterparts or have subtle morphologic features that could be overlooked by the pathologist.

Objective.—To present clues to the diagnosis of potentially deceptive malignancies, including desmoplastic malignant melanoma, nevoid malignant melanoma, subcutaneous lymphoma, metastatic breast carcinoma, and epithelioid sarcoma.

Data Sources.—Published literature and personal experience.

Conclusions.—Knowledge of commonly misdiagnosed cutaneous neoplasms will help the general surgical pathologist avoid these potential pitfalls in neoplastic dermatopathology.

Malignant melanoma in the 21st century, part 1: epidemiology, risk factors, screening, prevention, and diagnosis

Malignant melanoma is an aggressive, therapy-resistant malignancy of melanocytes. The incidence of melanoma has been steadily increasing worldwide, resulting in an increasing public health problem. Exposure to solar UV radiation, fair skin, dysplastic nevi syndrome, and a family history of melanoma are major risk factors for melanoma development. The interactions between genetic and environmental risk factors that promote melanomagenesis are currently the subject of ongoing research. Avoidance of UV radiation and surveillance of high-risk patients have the potential to reduce the population burden of melanoma. Biopsies of the primary tumor and sampling of draining lymph nodes are required for optimal diagnosis and staging. Several clinically relevant pathologic subtypes have been identified and need to be recognized. Therapy for early disease is predominantly surgical, with a minor benefit noted with the use of adjuvant therapy. Management of systemic melanoma is a challenge because of a paucity of active treatment modalities. In the first part of this 2-part review, we discuss epidemiology, risk factors, screening, prevention, and diagnosis of malignant melanoma. Part 2 (which will appear in the April 2007 issue) will review melanoma staging, prognosis, and treatment.