Validity of the histopathological criteria used for diagnosing dysplastic naevi. An interobserver study by the pathology subgroup of the EORTC Malignant Melanoma Cooperative Group

Dysplastic nevus part I: Historical perspective, classification, and epidemiology

Since the late 1970s, the diagnosis and management of dysplastic nevi have been areas fraught with controversy in the fields of dermatology and dermatopathology. Diagnostic uncertainty and lack of standardized nomenclature continue to propagate confusion among clinicians, dermatopathologists, and patients. In part I of this CME review article, we summarize the historical context that gave rise to the debate surrounding dysplastic nevi and review key features for diagnosis, classification, and management, as well as epidemiology. We discuss essentials of clinical criteria, dermoscopic features, histopathologic features, and the diagnostic utility of total body photography and reflectance confocal microscopy in evaluating dysplastic nevi, with emphasis on information available since the last comprehensive review a decade ago.

Analysis of interobserver reproducibility in grading dysplastic nevi: Results of the application of the 2018 World Health Organization grading criteria

BACKGROUND

We aimed to determine whether the histopathological grading of dysplastic nevi is an objective endeavor, considering interobserver variability, according to 2018 World Health Organization (WHO) criteria.

METHODS

In total, 179 cases of dysplastic nevi, with high and moderate degree of atypia, diagnosed and graded according to the previous criteria were reviewed by three pathologists. Then, the observers graded the dysplastic nevi as low or high according to 2018 WHO criteria.

RESULTS

Grading of dysplastic nevi was in complete agreement in 99 out of 179 cases across three observers with a fair level of overall interobserver agreement (multirater κ_free : 0.40). The observers showed moderate to good agreement for most of the architectural features, except for criteria regarding focal continuous basal proliferation of melanocytes, density of non-nested junctional melanocytes, and presence of dyscohesive nests of intraepidermal melanocytes, whereas fair agreement was achieved for the cytological criteria.

CONCLUSIONS

The 2018 WHO criteria for dysplastic nevus will ensure a common approach to the diagnosis and grading of dysplastic nevi. However, histopathological criteria, such as cytological features and focal continuous basal proliferation of melanocytes, should be improved so as to ensure a more accurate surgical approach and risk assessment.

Dysplastic Nevi: Morphology and Molecular and the Controversies In-between

Dysplastic nevi are distinctive melanocytic lesions in the larger group of atypical nevi. They often are multiple and sporadic with genetic features intermediate between common acquired nevi and melanoma. Dysplastic nevi may be multiple, familial, and seen in patients with familial melanoma syndrome. Although their behavior is benign, they rarely represent a precursor to melanoma. If clinically suspicious, dysplastic nevi should be removed for adequate histopathologic examination and to exclude possibility of melanoma. Partial sampling should be avoided because reliable separation from melanoma requires visualization of the entire lesion to allow for examination of architectural histopathologic features and avoid sampling error.

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.

Histopathologic Interobserver Agreement on the Diagnosis of Melanocytic Skin Lesions with Equivocal Dermoscopic Features: A Pilot Study

Aims and background

Dermoscopy (dermatoscopy, skin surface microscopy, epiluminescence microscopy) has been increasingly employed in recent years for the preoperative detection of cutaneous melanoma, and dermatoscopic features of pigmented skin lesions have been previously defined using histopathology (HP) as the “key to the code”. The aim of the present study was to evaluate the interobserver agreement on the HP diagnosis in a series of epiluminescence microscopy equivocal melanocytic skin lesions.

Study design

Ten melanocytic skin lesions were selected on the basis of diagnostic disagreement of at least 2 out of 9 epiluminescence microscopy observers. The histologic specimens from the 10 lesions were examined by 9 HP observers. The agreement of the HP diagnoses was calculated by means of Fleiss' k statistics.

Results

The overall HP agreement was less than excellent (k = 0.5). When considering the prevailing epiluminescence microscopic and HP diagnoses, 2 cases were shown to be epiluminescence microscopy false-negative melanomas. Virtually no agreement was found among epiluminescence microscopy observers in 4 cases (40%) or among HP observers in 3 cases (30%). However, only one pigmented skin lesion remained un-classifiable on epiluminescence microscopy as well as HP.

Conclusions

When at least 2 epiluminescence microscopy experts disagree in the evaluation of a given melanocytic skin lesion, even HP consultations may give equivocal results. The need to establish more reliable epiluminescence microscopic and HP criteria by performing an improved and meticulous clinicopathologic correlation, e.g. by using telecommunication via Internet, is emphasized.

The management of dysplastic naevi: a survey of Australian dermatologists

BACKGROUND/OBJECTIVES

The management of dysplastic naevi based on histopathological grading is a contentious issue. Comprehensive management guidelines are lacking and the approach taken varies between clinicians. The authors sought to understand how Australian dermatologists approach the management of biopsy-proven dysplastic naevi, and the impact of grading of dysplasia upon this management.

METHODS

In total, 547 Fellows of the Australasian College of Dermatologists were surveyed and 218 responses were collected (40% response rate).

RESULTS

Although all dermatologists surveyed would re-excise an incompletely removed severely dysplastic naevus, opinion was divided over whether to treat such a lesion as an in situ melanoma or a dysplastic naevus, with 55% of respondents using a 5-mm margin and the remainder opting for narrow margin re-excision. When the same lesion was reported to be clear of margins by 1 mm after biopsy and the clinical suspicion for melanoma was high, 44% would re-excise with a 5-mm margin.

CONCLUSIONS

The approach of Australian dermatologists to the management of dysplastic naevi varies between clinicians, reflecting the problems raised by the validity of histopathological grading.

Collagen Anomalies as Clues for Diagnosis: Part 1

BACKGROUND

Collagen is the most abundant protein in the body and the main structural component of the skin.

OBJECTIVE

To provide a review of the histopathology of collagen alterations and to propose a classification with the most important types of collagen anomalies in dermatopathology. The authors describe some of the main morphological clues of collagen anomalies for specific diagnosis of some cutaneous inflammatory and neoplastic conditions.

METHODS

The authors review histopathologic collagen anomalies, concerning both morphology and disposition in some inflammatory and neoplastic cutaneous conditions, and they review previous terminology and proposed a classification of the most important types of collagen anomalies that can be seen in dermatopathological practice.

RESULTS

Collagen anomalies in skin can be classified into lamellar fibrosis, sclerosis, and "balls" and "rings" of collagen. Lamellar fibrosis presents as long and thin collagen bundles forming a delicate network, which can be disposed in a parallel pattern, onion-bulb-like pattern, and storiform pattern. Sclerosis is characterized by large, thick, and eosinophilic bundles of collagen, which may present as a homogenous-diffuse pattern or as individual thick bundles of collagen with few or abundant number of fibroblasts between them. Finally, the authors propose the terms "balls" and "rings" of collagen. The term "balls" of collagen stands for thick, homogenous, eosinophilic, globular collagen bundles, with no distinguishable individual composing fibers, which include the floating sign and the free-floating sign. The term "rings" of collagen is characterized by sclerotic collagen arranged in a homogenous rimming pattern around vessels without independent fibers in its composition.

CONCLUSIONS

Collagen anomalies may be important clues to establish specific clues for specific diagnoses in dermatopathology.

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.

Discordance of histopathologic parameters in cutaneous melanoma: Clinical implications

BACKGROUND

Histopathologic analysis remains the gold standard for the diagnosis of melanoma, however previous studies have shown a substantial rate of interobserver variability in the evaluation of melanocytic lesions.

OBJECTIVE

We sought to evaluate discordance in the histopathological diagnosis and microstaging parameters of melanoma and subsequent impact on clinical management.

METHODS

This was a retrospective review of 588 cases of cutaneous melanoma and melanoma in situ from January 2009 to December 2014 that were referred to Emory University Hospital, Atlanta, GA, for treatment. Per institutional policy, all outside melanoma biopsy specimens were reviewed internally. Outside and institutional reports were compared.

RESULTS

Disagreement between outside and internal reports resulted in a change in American Joint Committee on Cancer pathologic stage in 114/588 (19%) cases, resulting in a change in management based on National Comprehensive Cancer Network guidelines in 105/588 (18%) cases.

LIMITATIONS

Given the retrospective nature of data collection and the bias of a tertiary care referral center, cases in this study may not be representative of all melanoma diagnoses.

CONCLUSION

These findings confirm consistent subjectivity in the histopathologic interpretation of melanoma. This study emphasizes that a review of the primary biopsy specimen may lead to significant changes in tumor classification, resulting in meaningful changes in clinical management.

Dysplastic nevi and melanoma

Dysplastic nevi are described as being on a continuum between common acquired nevi and melanoma because they are morphologically and biologically intermediate between these 2 entities. Since initially being reported as histologic lesions observed in melanoma-prone families, there has been considerable debate about the definition of dysplastic nevi, the histologic and clinical criteria used to define them, and their biologic importance. Their role as precursor lesions for melanoma is not their primary role in their relationship to melanoma because of the rarity of transformation of any individual nevus to a melanoma. Although there is still no single, universally agreed upon histologic or clinical definition or even name for these nevi, dysplastic nevi should be considered important because of their association with an increased risk for melanoma.

NRAS and BRAF mutations in melanoma-associated nevi and uninvolved nevi

According to the prevailing multistep model of melanoma development, oncogenic BRAF or NRAS mutations are crucial initial events in melanoma development. It is not known whether melanocytic nevi that are found in association with a melanoma are more likely to carry BRAF or NRAS mutations than uninvolved nevi. By laser microdissection we were able to selectively dissect and genotype cells either from the nevus or from the melanoma part of 46 melanomas that developed in association with a nevus. In 25 cases we also genotyped a control nevus of the same patients. Available tissue was also immunostained using the BRAF^V600E-mutation specific antibody VE1. The BRAF^V600E mutation was found in 63.0% of melanomas, 65.2% of associated nevi and 50.0% of control nevi. No significant differences in the distribution of BRAF or NRAS mutations could be found between melanoma and associated nevi or between melanoma associated nevi and control nevi. In concordant cases immunohistochemistry showed a higher expression (intensity of immunohistochemistry) of the mutated BRAF^V600E-protein in melanomas compared to their associated nevi. In this series the presence of a BRAF- or NRAS mutation in a nevus was not associated with the risk of malignant transformation. Our findings do not support the current traditional model of stepwise tumor progression.

The dysplastic nevus: from historical perspective to management in the modern era: part I. Historical, histologic, and clinical aspects

Since its description in the 1970s, the dysplastic nevus has been a source of confusion, and whether it represents a precursor to melanoma remains a controversial subject. Although a Consensus Conference in 1992 recommended that the term "dysplastic nevus" no longer be used, the histologic diagnosis continues to present a therapeutic quandary for dermatologists and other physicians, and there remains significant variation in clinical management. In part I of this continuing medical education review, we will discuss the historical origins of the term, the evidence for its distinct histologic basis, and its clinical significance.

Dysplastic nevi

Dysplastic nevi have been a subject of much debate since their original description in 1978. Although some question the biological potential of dysplastic nevi themselves, several studies have shown that their presence confers substantial risk for melanoma. In addition to predisposing patients to melanoma, dysplastic nevi have been shown to harbor genetic mutations, indicating their position on a continuum between banal nevi and melanomas. Dysplastic nevi are also clinically relevant as mimickers of melanoma, and can be challenging diagnostically. This article reviews the history, epidemiology, biology and genetics, clinical features, histopathologic features, and management guidelines for patients with these lesions.

Dysplastic naevi: an update

Dysplastic naevi are clinically atypical and histologically are characterized by architectural disorder and cytological atypia. Their diagnosis is reproducible if criteria and thresholds are agreed upon. They are significant only in relation to melanoma, as simulants of melanoma, as markers of individuals at increased risk of developing melanoma, and as potential and occasional actual precursors of melanoma. Morphologically and biologically, they are intermediate between common naevi and melanoma. Individuals with dysplastic naevi may have deficient DNA repair, and dysplastic naevi lesions are associated with overexpression of pheomelanin, which may lead to increased oxidative damage and increased potential for DNA damage and tumour progression.

Pigmented lesion pathology: what you should expect from your pathologist, and what your pathologist should expect from you

The first part of this review examines the reliability of histologic diagnosis in pigmented lesions, as measured by concordance studies and medicolegal analysis. It emphasizes the role of clinicians in maximizing that reliability, by providing adequate clinical descriptions, using appropriate biopsy technique, and critically interpreting pathology reports. It identifies those entities that are especially problematic, either because they cannot be reliably recognized by the histopathologist or because their histology is a poor guide to their biologic behavior. The second part of the review is a guide to some of the more difficult and controversial pigmented lesions, including dysplastic nevus, spitzoid nevi and melanomas, cellular blue nevus, animal-type melanoma, and deep penetrating nevus.

The "dysplastic" nevus

Dysplastic nevi have become an increasing focus clinically, with evidence that they are associated with a higher risk of developing melanoma. However, there still is contention regarding the significance of dysplastic nevi. This contribution provides an overview of the history, epidemiology, genetics, clinical and histologic features, and procedures for clinical management of dysplastic nevi. Since dysplastic nevi were described originally in 1978, a great deal of research has examined the epidemiology of these lesions and the genetic factors related to the development of dysplastic nevi. However, there is disagreement regarding the clinical management of dysplastic nevi and the histologic definition of dysplastic nevi. Current recommendations include preventative measures, such as sun protection and careful surveillance and biopsies of suspicious lesions as needed. The advent of new technologies, such as computer-vision systems, have the potential to significantly change treatment of dysplastic nevi in the future.

Reliability of the histopathologic diagnosis of keratinocyte carcinomas

OBJECTIVE

We sought to determine the interobserver reliability of the histopathologic diagnosis of basal cell carcinoma (BCC) and squamous cell carcinoma (SCC) (keratinocyte carcinomas) in the setting of a Department of Veteran Affairs multicenter chemoprevention study.

METHODS

Interobserver concordance was assessed by blinded review of histopathologic slides by study dermatopathologists.

RESULTS

Overall interobserver agreement between the two dermatopathogists was kappa = 0.69 (95% confidence interval [CI] 0.67-0.69). The dermatopathologists' interobserver agreement was highest for basal cell carcinoma at kappa = 0.88 (95% CI 0.84-0.91) and for a diagnostic category in the SCC-actinic keratosis spectrum at kappa = 0.80 (95% CI 0.73-0.86). The largest disagreements between the two reference dermatopathologists were regarding the categories of invasive SCC at kappa = 0.62 (95% CI 0.52-0.72), SCC in situ at kappa = 0.42 (95% CI 0.29-0.56), and actinic keratosis at kappa = 0.51 (95% CI 0.40-0.62). Agreement between the local pathologists and central reference dermatopathologists were similar to the agreement between the central dermatopathologists. The morphea subtype of basal cell carcinoma was the only reliably diagnosed subtype (kappa = 0.79, 95% CI 0.51-1.00), and tumor depth was reliably measured.

LIMITATIONS

A limitation of this study was the use of only two reference dermatopathologists.

CONCLUSION

Because of the impact on physician decision making and patient care, researchers and clinicians need to be aware of reliability of histopathology results, particularly pertaining to the SCC and actinic keratosis spectrum.

Atypical nevi of the scalp in adolescents

BACKGROUND

A few reports in the literature point out that in special areas of the body, nevi can have peculiar pseudomelanomatous features. In our routine work, we have met few examples of atypical nevi with peculiar features on the scalp of teenagers. To evaluate the frequency and the biological behaviour of these lesions, we have conducted a complete survey on melanocytic lesions on the scalp in a significant group of patients.

MATERIALS AND METHODS

Thirty-nine nevi of the scalp were from adolescents (12-18 years), 160 from adults, and 30 from children below the age of 12 years.

RESULTS

About 10% of the melanocytic nevi of the scalp of adolescents have atypical cytological and architectural aspects that are different from those seen in Clark's dysplastic nevus. The most striking features were the presence of large bizarrely shaped nests scattered disorderly along the junction with follicular involvement. Other findings were pagetoid spread of cells above the junction and the discohesive pattern of the melanocytes in the nests. Mild cytological atypia was present but less significant. Such distinctive aspects are not found in nevi of the same site in adults or younger children. The general pattern of these atypical nevi of the scalp of adolescents closely recalls that of the so-called atypical nevi on special sites, i.e. nevi on mammary line, genitalia and body's folds. Despite the architectural and cytological atypia, clinical follow-up does not show any tendency to recur or proclivity to malignant behaviour.

CONCLUSIONS

Despite their similarities with melanoma, the nevi with atypical features of the scalp of adolescents are probably an entirely benign entity, at least at the moment of their excision. However, although benign, the relationship of this peculiar group of nevi with melanomas developed in adulthood remains entirely unknown, and the complete excision with conservative margins seems a recommendable procedure.

Dysplastic naevi with moderate to severe histological dysplasia: a risk factor for melanoma

BACKGROUND

The risk of malignant melanoma associated with histologically dysplastic naevi (HDN) has not been defined. While clinically atypical naevi appear to confer an independent risk of melanoma, no study has evaluated the extent to which HDN are predictive of melanoma.

OBJECTIVES

To estimate the risk of melanoma associated with HDN. Secondarily, the risk associated with number of naevi and large naevi is estimated.

METHODS

We enrolled 80 patients with newly diagnosed melanoma along with 80 spousal controls. After obtaining information on melanoma risk factors and performing a complete cutaneous examination, the most clinically atypical naevus was biopsied in both cases and controls. Histological dysplasia was then assessed independently by 13 dermatopathologists (0, no dysplasia; 1, mild dysplasia; 2, moderate dysplasia; 3, severe dysplasia). The dermatopathologists were blinded as to whether the naevi were from melanoma subjects or controls. Multivariate analyses were performed to determine if there was an independent association between the degree of histological dysplasia in naevi and a personal history of melanoma.

RESULTS

In persons with naevi receiving an average score of > 1 (i.e. naevi considered to have greater than mild histological dysplasia), there was an increased risk of melanoma [odds ratio (OR) 2.60, 95% confidence interval (CI) 0.99-6.86] which persisted after adjustment for confounders (OR 3.99, 95% CI 1.02-15.71). Very few dermatopathologists reliably graded naevi of subjects with melanoma as being more dysplastic than naevi of control subjects. Among the entire group, the interobserver reliability associated with grading histological dysplasia in naevi was poor (weighted kappa 0.28).

CONCLUSIONS

HDN do appear to confer an independent risk of melanoma. However, this result may add more to our biological understanding of melanoma risk than to clinical assessment of risk, because HDN assessed by a single pathologist generally cannot be used to assess risk of melanoma. Future studies should be directed at establishing reproducible, predictive criteria for grading naevi.

Precursors to melanoma and their mimics: nevi of special sites

Melanocytic nevi, which are benign tumors of melanocytes, may have occasional cosmetic significance but, for the most part, they are important only in relation to melanoma. Nevi are the most important simulants of melanoma, both clinically and histologically, and can usually be reliably distinguished from melanomas using published criteria. Some lesions are characterized by greater degrees of atypia and may be more difficult to diagnose. Dysplastic nevi are among the most important simulants of melanoma. Nevi may also be important as potential precursors of melanoma; however, most nevi are stable and will not progress to malignancy. Nevi are vastly more common than melanomas and the rate of progression of individual lesions is very low. Therefore, nevi are not as a rule managed by wholesale excision to prevent melanoma. Nevi are also important as risk markers, identifying individuals at greater risk of developing melanoma in the future. Dysplastic nevi and, to a lesser extent, common acquired and congenital nevi are among the most important melanoma risk markers. Nevi of special sites have been identified as nevi that may show atypical features suggestive of a dysplastic nevus or of a melanoma. However, they are not risk markers and they are not malignancies. Nevi of genital skin, acral skin, and flexural skin are among the most important 'nevi of special sites'. It is important, in considering the differential diagnosis of a lesion in a special site, to avoid overcalling such a lesion as a melanoma or a dysplastic nevus because this could lead to excessive treatment. Conversely, it is important to avoid undercalling a lesion that is a dysplastic nevus or a melanoma as a nevus of special sites, because in this circumstance a patient could lose the opportunity either for surveillance to recognize a developing melanoma at an early, curable stage, or for definitive treatment of an established malignancy. In this monograph, dysplastic nevi and nevi of special sites are compared and contrasted in relation to melanoma.

Interobserver reproducibility of histological features in cutaneous malignant melanoma

AIMS

To assess the interobserver reproducibility of certain histological features proposed for the diagnosis of melanoma.

METHODS

In a series of melanomas, 13 histological parameters were analysed: dimension > 6 mm, asymmetry, poor circumscription, irregular confluent nests, single melanocytes predominating, absence of maturation, suprabasal melanocytes, asymmetrical melanin, melanin in deep cells, cytological atypia, mitoses, dermal lymphocytic infiltrate, and necrosis.

RESULTS

The agreement (reproducibility) between the nine observers was excellent (kappa > 0.75) for 10 of the 13 examined features (dimension > 6 mm, poor circumscription, irregular confluent nests, single melanocytes predominating, absence of maturation, suprabasal melanocytes, asymmetrical melanin, melanin in deep cells, mitoses, and necrosis). The agreement for asymmetry was very close to excellence (kappa = 0.74), and that for cytological atypia (kappa = 0.65) and dermal lymphocytic infiltrate (kappa = 0.47) was slightly lower, but in the fair to good agreement range. The kappa values obtained by comparison with the majority diagnosis were generally high (> or = 0.85); the mean value of kappa was lower (0.70) for only one parameter (dermal lymphocytic infiltrate).

CONCLUSIONS

The parameters investigated showed an overall good reproducibility.

Histologic similarities between lentigo maligna and dysplastic nevus: importance of clinicopathologic distinction

BACKGROUND

Lentigo maligna (LM) can histologically simulate dysplastic nevus (DN). Partial biopsy of LM may lead to misdiagnosis.

METHODS

One hundred and fourteen cases of LM and LM melanoma (LMM) were diagnosed at the Veterans Affairs Palo Alto Health Care System (1993-2002). Biopsy and excision specimens for 68 in situ and 28 invasive melanomas were classified as having predominant classical LM features, predominant DN-like morphology, or a mixed pattern.

RESULTS

Biopsy specimens demonstrated a predominant classical pattern in 38% (25/65) LM and 36% (10/28) LMM, predominant DN-like features in 43% (28/65) LM and 25% (7/28) LMM, and mixed pattern in 15% (10/65) LM and 29% (8/28) LMM. Most LM and LMM biopsies were partial. Significant DN-like features were present in 51% LM and 57% LMM excision specimens. Median age was 72 years for LM and 73 years for LMM, mean lesion diameters were 1.3 and 1.7 cm for LM and LMM, respectively, and 85% of LM and 75% of LMM cases were located on heavily sun-exposed sites.

CONCLUSIONS

Misdiagnosis of LM or LMM as DN could have devastating results. Large pigmented lesions on sun-damaged skin in elderly individuals should warrant consideration of LM/LMM diagnosis, even in the setting of DN-like features histologically. Excisional biopsy may help to avoid misdiagnosis.

Histological features used in the diagnosis of melanoma are frequently found in benign melanocytic naevi

AIMS

The histological features used in the diagnosis of melanoma may be present in benign naevi, but quantitative data are not available. The aim of this study was to establish the real prevalence of such features in naevi.

METHODS

Ten dermatopathologists, from nine Italian institutions, studied a series of naevi. Eleven histological parameters currently used in melanoma diagnosis were analysed: asymmetry, poor circumscription, predominance of single melanocytes, irregular confluent nests, suprabasal melanocytes, hair follicle involvement, absence of maturation, cytological atypia, dermal lymphocytic infiltrate, mitoses, and necrosis.

RESULTS

Ninety one naevi were examined: 22 junctional, 59 compound, and 10 intradermal. None of the studied parameters was seen in 22 of the benign naevi studied. One or more investigated features were found in 69 naevi. Poor circumscription was found in 49 cases, single melanocytic predominating in 42, asymmetry in 41, irregular confluent nests in 16, cytological atypia in 14, suprabasal melanocytes in seven, and hair follicle involvement in seven; absence of maturation, mitoses and necrosis were not found.

CONCLUSIONS

The histological features used for the histological diagnosis of melanoma are often present in benign melanocytic naevi. This suggests a critical, non-mechanical use of them in melanoma diagnosis.

Current diagnostic problems in melanoma pathology

The histopathological diagnosis of cutaneous melanocytic lesions may be difficult to assess. Frequently encountered diagnostic problems include: 1) Dysplastic nevus or melanoma in situ?; 2) Melanoma in situ or superficial spreading melanoma?; 3) Lentigo maligna or lentigo maligna melanoma?; 4) Compound nevocellular nevus or nevoid melanoma?; and 5) Spitz nevus or Spitzoid melanoma? Moreover, less frequently encountered diagnostic challenges are discussed: 1) Deep penetrating nevus or nodular melanoma?; and 2) Cellular blue nevus or melanoma metastasis? In this contribution, these problems are discussed after a systematic approach involving a concise histopathological description of the classic lesions considered in the differential diagnoses, a presentation of the deviating histopathological features that give rise to the diagnostic problems, and finally diagnostic recommendations on the classification of the problematic lesions. We also briefly discuss the contribution of additional immunohistochemistry and molecular pathology in aiding to establish a correct diagnosis.

The dilemma of the dysplastic nevus

There are few areas in dermatology that provoke as much controversy as dysplastic nevus. Over the past decade, there have been significant strides made in terms of understanding the biology and etiology of the lesion. Distinct and reliable clinical and histologic features have been delineated. In this article, the management of patients with dysplastic nevi and the role for dermoscopy, photographic surveillance, genetic mapping and counseling, chemoprevention, and nevi removal are discussed.

Dermoscopic and histopathologic diagnosis of equivocal melanocytic skin lesions: an interdisciplinary study on 107 cases

BACKGROUND

Dermoscopy (dermatoscopy, epiluminescence microscopy) is increasingly employed for the preoperative detection of cutaneous melanoma; dermoscopic features of pigmented skin lesions have been previously defined using histopathology as the key to the code. In a preliminary study on 10 cases evaluated by nine dermoscopists and nine histopathologists, the authors experienced that when at least two dermoscopists disagree in evaluating a melanocytic lesion, even histopathologic consultations may give equivocal results.

METHODS

One hundred seven melanocytic skin lesions, consecutively excised because of equivocal clinical and/or dermoscopic features, were retrospectively examined by eight dermoscopists and eight histopathologists; the diagnostic interobserver agreement was calculated by means of the Schouten k statistics. After histopathologic consultations, all 107 lesions underwent unblinded dermoscopic re-evaluation in order to find which dermoscopic features had given rise to histopathologic diagnostic difficulties.

RESULTS

The interobserver ageement was good for both dermoscopy (k = 0.53) and histopathology (k = 0.74). Out of 48 cases evaluated by the dermoscopists in complete accordance, only 8 (16.7%) received at least one conflicting histopathologic diagnosis. Instead, among the remaining 59 cases with at least one disagreeing dermoscopic diagnosis, 21 (35.6%) received at least one disagreeing histopathologic diagnosis. The unblinded dermoscopic re-evaluation showed that five out of seven lesions with clear-cut regression structures were histopathologically controversial.

CONCLUSIONS

At least for selected and reasonably difficult lesions, a diagnostic discrepancy among formally trained dermoscopists seems to be predictive for a diagnostic disagreement among histopathologists. Lesions showing clear-cut regression structures are prone to give some histopathologic disagreement.

Spitz naevi may express components of the plasminogen activation system

The plasminogen activation (PA) system is involved in the process of invasion and metastasis. Its major components are urokinase (uPA) and tissue-type plasminogen activator (tPA), plasminogen activation inhibitor type 1 and 2 (PAI-1 and PAI-2) and a receptor for urokinase (uPAR). In this study, the expression of plasminogen activation components in Spitz naevi was compared with that in common and dysplastic naevi on the one hand and primary cutaneous melanomas on the other. Spitz naevi had melanocytic positivity for uPA in 0% (0/36), tPA in 30% (6/20), PAI-1 in 10% (3/35), PAI-2 in 40% (8/21) and uPAR in 60% (13/21) of cases. This far exceeded the expression found in common (n = 25) and dysplastic (n = 15) naevi, which only showed melanocytic positivity for PAI-2 (20% and 15% respectively) and in one dysplastic naevus also for uPAR. This was much (for most components significantly) less than the proportion of primary melanomas with tumour cell positivity, which was 30% (11/38) for uPA, 80% (19/24) for tPA, 75% (28/38) for PAI-1, 80% (19/24) for PAI-2 and 80% (19/24) for uPAR. The main findings of this study are that Spitz naevi, firstly, may express plasminogen activator (tPA), inhibitors and the receptor of the PA system, but in a much smaller proportion than cutaneous melanomas; and secondly, do not express urokinase, whereas some of the melanomas do. uPA positivity may therefore be suggestive of melanoma. However, overlapping staining results imply that the PA system has limited value in the differential diagnosis between Spitz naevus and primary melanoma. As serine protease components are expressed, Spitz naevi may use this proteolytic machinery to accomplish matrix degradation, although in a more restricted, possibly transient manner than melanomas.

A natural history of melanomas and dysplastic nevi: an atlas of lesions in melanoma-prone families

BACKGROUND

Few long-term clinical and histologic data for melanocytic lesions have been available based on the mutation status of families at an increased risk of melanoma. In the current study, the authors describe the clinical and histologic features of dysplastic nevi and melanoma over time in families at an increased risk of melanoma with differing germline mutations in CDKN2A, CDK4, or not yet identified genes.

METHODS

Thirty-three families with > 2 living members with invasive melanoma were evaluated clinically and followed prospectively for up to 25 years. All the participants were evaluated by the same study team at the Clinical Center of the National Institutes of Health or in local clinics. After informed consent was obtained, family members (n = 844) were examined and photographed. Blood was obtained for genetic studies; genotyping for CDKN2A and CDK4 was performed. Sequential photographs of melanocytic lesions were taken as part of the clinical evaluations. When melanocytic lesions were removed, the histology was reviewed. Representative photographs and photomicrographs were selected for six classes of lesions and three mutation groups.

RESULTS

All the families were found to have members with dysplastic nevi and melanoma; 17 had mutations in CDKN2A, 2 had mutations in CDK4, and 14 had no mutations in either gene identified. The majority of dysplastic nevi either remain stable or regress; few change in a manner that should cause concern for melanoma. With careful surveillance, melanomas can be found early.

CONCLUSIONS

The melanomas and dysplastic nevi that were found to occur in the study families did not appear to vary by the type of mutation identified in the families.

Inter-observer variation in the histopathological diagnosis of clinically suspicious pigmented skin lesions

When a biopsy is taken of a suspicious pigmented skin lesion, histological examination is expected to establish the definitive diagnosis. This study evaluated the inter-observer variation of 20 pathologists in the histological diagnosis of a randomly selected set of suspicious pigmented skin lesions (PSLs), by comparing their diagnoses to a reference diagnosis. Overall sensitivity for melanoma was 87%, ranging from 55% to 100% between the observers. Sensitivity was significantly lower for thin (Breslow thickness <1 mm) than for thick melanomas (83% versus 97%, p=0.005). Overall melanoma specificity was 94%, ranging from 83% to 100% between observers. Dysplastic naevus was the most important source of false-positive diagnoses, mainly in situ melanomas. Positive and negative predictive values in the given test set were 75% and 97%, respectively. In the case of melanoma, there was quite some variation in measured Breslow thickness. This would have led to a different therapeutic approach in 12% of the readings. Some of the variation seemed to be due to a different interpretation of the presence of a co-existent naevus. In 9% (3/35) of the readings, participants did not agree on the presence of ulceration. These results reflect a tendency to overdiagnose mainly thin melanomas in general histopathological practice. They also demonstrate variation in the assessment of major prognostic factors of melanoma.

The EORTC Melanoma Group: a comprehensive melanoma research programme by clinicians and scientists. European Organisation for Research and Treatment of Cancer

The EORTC Melanoma Group (MG) was founded in 1969 by both clinicians and scientists from various disciplines and fields of research with a common interest in malignant melanoma. This collaborative approach has always been the foundation of the groups strength. With an interest in tumour biology and especially the immunological aspects of the disease, the group has always pursued a scientific approach to treatment development in malignant melanoma. Over the years, the group has performed many clinical trials, epidemiological studies, histopathological studies defining standards and guidelines, translational research regarding prognostic factors and various metastatic and immunological aspects of melanoma, and developed quality assurance programmes for immunological and molecular biological assays in laboratory networks. At present, the EORTC MG runs the worldwide largest clinical trial programme in stages II, III and IV melanoma involving some 140 cancer centres in and outside Europe. Each trial is associated with the appropriate translational research programmes.

Critical analysis of histologic criteria for grading atypical (dysplastic) melanocytic nevi

Low concordance in grading atypical (dysplastic) melanocytic nevi (AMN) has been reported, and no systematic evaluation is available. We studied 123 AMN with architectural and cytologic atypia (40 associated with atypical-mole syndrome), classified according to standard criteria by 3 independent observers. Histologic variables included junctional and dermal symmetry, lateral extension, cohesion and migration of epidermal melanocytes, maturation, regression, nuclear features, nuclear grade, melanin, inflammatory infiltrate location, and fibroplasia. AMN (43 junctional and 80 compound) were graded mild (31), moderate (61), and severe (31). AMN-severe correlated with 3 or more nuclear abnormalities (especially pleomorphism, heterogeneous chromatin, and prominent nucleolus) and absence of regression, mixed junctional pattern, and suprabasilar melanocytes on top of lentiginous hyperplasia. AMN-severe diagnostic accuracy was 99.5% using these criteria, but only the absence of nuclear pleomorphism differentiated AMN-mild from AMN-moderate. No architectural features distinguishing AMN-mild from AMN-moderate were selected as significant by the discriminant analysis. AMN from atypical-mole syndrome revealed subtle architectural differences, but none were statistically significant in the discriminant analysis. Histologic criteria can reliably distinguish AMN-severe but fail to differentiate AMN-mild from AMN-moderate. AMN from atypical-mole syndrome cannot be diagnosed using pathologic criteria alone.

Dysplastic nevi of the scalp and forehead in children

To determine if there is a significant difference in the relative frequency and degree of atypia of sporadic dysplastic nevi from the scalp, face, and neck area in children as compared with nevi from the rest of the body, we reviewed 99 consecutive biopsy specimens of melanocytic nevi from the scalp, face, and neck areas in children less than 18 years of age and compared them with 95 consecutive cases of nevi from other areas of the body in children of the same age. Large numbers of the nevi biopsied from the scalp (13 of 31; 41.93%) and forehead (2 of 10; 20%) were dysplastic. The number of dysplastic nevi from the neck (1 of 58; 1.72%) was not assessed as very different from the incidence found in other regions of the body, where 7 dysplastic nevi (7.36%) from a total of 95 nevi were found. Of the 13 dysplastic nevi from the scalp, 9 showed minimal atypia and 4 showed moderate atypia. No nevi with severe atypia were found. Many pigmented nevi from the scalp and forehead in children in this study were dysplastic. This finding points out the importance of examining the scalp of children for the presence of dysplastic nevi. The majority of nevi from the neck were common nevi.

Atypical histologic features in melanocytic nevi

The atypical histologic features considered to be specific to dysplastic (atypical) nevi have been reported to occur in nevi that are common nevi by all other clinical and histologic features. The distribution and mutual relations among such features in nevi need to be further studied. Six histologic features (dimension > 5 mm, lentiginous proliferation, disordered nested pattern, melanocytic dyskaryosis, dermal lymphocytic infiltrate, suprabasal melanocytes) were analyzed in 253 melanocytic nevi with different clinical appearances. Atypical histologic features, found in 72% of nevi, occurred singly or formed numerous and highly variable combinations. Nevi formed a complex histologic spectrum comprising lesions showing a progressively increasing incidence of atypical features rather than two classes (common and dysplastic nevi). To divide the investigated lesions in objectively defined groups, we used a scoring system. In each nevus, a numeric value of 1 was assigned when each of the studied parameters was present and a value of 0 was assigned when each of these parameters was absent; on the basis of the final scores, nevi were divided in six different classes (classes 0-5). Diagnostic categories such as dysplastic nevi and common nevi seem to be inappropriate, as they do not reflect the real histologic complexity of such lesions.

The genetics of hereditary melanoma and nevi. 1998 update

Although the first English-language report of melanoma in 1820 contained a description of a melanoma-prone family, it was 1983 before formal genetic analysis suggested an autosomal dominant mode of inheritance for both melanoma and the then newly described melanoma precursor, dysplastic nevi (DN). Subsequent genetic studies have assumed this model to be correct, although when viewed in aggregate, the data are inconsistent. The first proposed melanoma gene (CMM1) was mapped to chromosome 1p36. This gene assignment has not been confirmed. A second melanoma gene, designated CMM2, has been mapped to chromosome 9p21. This gene assignment has been confirmed, and the cell cycle regulator CDKN2A has been proposed as the candidate gene. Germline mutations in this gene have been identified in about 20% of melanoma-prone families that have been studied to date. Pancreatic cancer occurs excessively in melanoma families with germline mutations in CDKN2A. Germline mutations in the cyclin-dependent kinase gene CDK4 (chromosome 12q14) have been described in three melanoma families. This finding represents a third melanoma gene but one that accounts for only a tiny fraction of all hereditary melanoma. Recently, a familial melanoma-astrocytoma syndrome has been reported. Large germline deletions of 9p21 occur in these families, with the p19 gene implicated in its pathogenesis. At present, clinical predictive genetic testing for mutations in the CDKN2A gene is available commercially, but its use has been limited by uncertainty as to how test results would affect the management of melanoma-prone family members. Currently, management recommendations include monthly skin self-examination, clinical skin examination once or twice yearly, a low threshold for simple excision of changing pigmented lesions, moderation of sun exposure, and appropriate use of sunscreens. A heritable determinant for total nevus number has been suggested by twin studies. Other data suggest the presence of a major gene responsible for "total nevus density" in melanoma-prone families. Approximately 55% of the mole phenotype in multiplex melanoma families was explained by this proposed gene. An autosomal dominant mode of inheritance has been proposed for DN, and data exist to suggest that DN may be a pleiotropic manifestation of the 1p36 familial melanoma gene. However, there clearly are melanoma-prone families that do not express the dysplastic nevus trait, and some of the families linked to CDKN2A also present with dysplastic nevi. Several studies have shown a surprisingly high prevalence of DN on the skin of family members of probands with DN. In light of the extensive evidence documenting that persons with DN (both sporadic and familial) have an increased prospective risk of melanoma, these family studies suggest that relatives of persons with DN should be examined for both DN and melanoma. Genetic determinants play a major role in the pathogenesis of normal nevi, DN, and melanoma. Identifying the molecular basis of these genetic events promises to enhance melanoma risk-reduction strategies and, ultimately, reduce melanoma-associated mortality.

The dysplastic naevus

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Systematic review of the diagnostic accuracy of dermatoscopy in detecting malignant melanoma

OBJECTIVE

To assess the evidence that dermatoscopy improves the accuracy of diagnosis of melanomas in clinical practice.

DATA SOURCES

MEDLINE 1983-January 1997, EMBASE 1980-1996, and bibliographies of retrieved articles.

STUDY SELECTION AND DATA EXTRACTION

Studies selected were original studies with formal methods and results sections comparing diagnostic accuracy of dermatoscopy for malignant melanoma with another clinical method; the criterion standard was excision biopsy with histopathological examination; and accuracy of dermatoscopic diagnosis was determined over a spectrum of stages of melanoma and skin lesions commonly confused with melanoma. Data were extracted by a single observer.

DATA SYNTHESIS

579 articles were identified; six studies met the inclusion criteria. Positive likelihood ratios for dermatoscopy for diagnosis of melanoma ranged from 2.9 to 10.3. Dermatoscopy had 10%-27% higher sensitivity than clinical diagnosis in the two studies with the most clinically equivocal lesions. However, when sensitivity of clinical diagnosis was more than 84%, sensitivity of dermatoscopy was only slightly higher. One study of dermatologists with no training in dermatoscopy showed a significant decrease in sensitivity.

CONCLUSIONS

Variability between studies in methods, observers and types of pigmented skin lesions and lack of studies in primary care make generalisation of results difficult. Dermatoscopy appeared not to improve the accuracy of diagnosis enough to alter the clinical management of most pigmented skin lesions. Further research with more explicit methods is needed.

Quality assessment by expert opinion in melanoma pathology: experience of the pathology panel of the Dutch Melanoma Working Party

Some cutaneous melanocytic lesions are notoriously difficult to diagnose by histopathology. For that reason, the Pathology Panel of the Dutch Melanoma Working Party was instituted and is regularly approached to provide an expert opinion on problem cases. In order to identify the most common diagnostic problems, 1069 consecutive referral cases of submitted lesions (1992 to 1994 inclusive) were analysed. About 60 per cent of the requests came from small laboratories, with up to three consultant pathologists. Two-thirds of the lesions reviewed concerned women and nearly 50 per cent of the patients were 30 years of age or younger. In 8 per cent of the cases, the referring pathologists felt unable to make a confident diagnosis; in 14 per cent, melanoma was suspected; and in 12 per cent, a differential diagnosis only had been formulated. The panel felt able to provide an unequivocal diagnosis in 93 per cent of the requests. Of the 158 lesions classified as 'invasive melanoma' by the referring pathologists, 22 were considered to be benign by the panel. Conversely, 108 invasive melanomas (panel diagnosis) had originally been considered as benign lesions, dysplastic naevi or melanoma in situ. These high numbers of discordancies reflect the intrinsic difficulty of the differential diagnoses in this selected material submitted to the panel. Diagnostic difficulties were most often encountered with Spitz naevi and dysplastic naevi. Although the rate of overdiagnosis and underdiagnosis is quite high, in the majority of cases the diagnosis of the referring pathologist matched the diagnosis of the panel. This may reflect a proper awareness of difficult melanocytic lesions in pathology practice. The activities of the Pathology Panel of the Dutch Melanoma Working Party contribute to the improvement of the quality of diagnosis in cutaneous melanocytic lesions, as they increase the number of unequivocal diagnoses and reduce the number of incorrect diagnoses. On the basis of the systematic comparison of the diagnosis by the referring pathologist and the panel, postgraduate teaching and quality control can be more focused on specific diagnostic problems.

Diagnostic discord with melanoma

The study of the Pathology Panel of the Dutch Melanoma Working Party highlights the great difficulty in achieving uniform diagnostic assessment of melanoma. Their solution is to set up a national reference panel and to focus continuing medical education on identified areas of particular difficulty. This could be appropriate for other countries, although selection of referees and funding may be problematic. It may also be timely to consider whether melanoma terminology can be rationalized to make it more likely to be reported consistently by pathologists whilst still providing sufficient information for proper patient management. Alternatively the reporting of most melanocytic lesions could be confined to pathologists who specialise in this subject, a practice which has evolved for other areas of pathology. This would facilitate the maintenance of standards and uniformity among that smaller group, but it would not avoid the need for a continuing awareness among all pathologists of the diagnostic pitfalls which abound in the area of melanocytic lesions.

Genetics of cutaneous melanoma and nevi

To provide a state-of-the-art summary of currently available data about the genetics of cutaneous melanoma and nevi, we reviewed the pertinent literature and outlined the important findings on genetic analyses. Although the first English-language report of melanoma in 1820 contained a description of a melanoma-prone family, seminal studies by investigators at the National Cancer Institute and the University of Pennsylvania identified dysplastic nevi (DN) as an important melanoma precursor, suggested an autosomal dominant mode of inheritance for both melanoma and DN, and proposed that a melanoma-susceptibility gene (CMM1) was located on chromosome 1p36. This gene assignment has not yet been confirmed by independent investigators. A second melanoma gene, designated CMM2, has been mapped to chromosome 9p21. This gene assignment has been confirmed independently, and the cell cycle regulator p16INK4a has been proposed as a candidate gene; germline mutations in this gene have been identified in about half of melanoma-prone families. Germline mutations in the cyclin-dependent kinase gene CDK4 (chromosome 12q14) have recently been described in two melanoma kindreds; this finding likely represents a third melanoma gene. A heritable determinant for total nevus number has been suggested, as has the presence of a major gene responsible for total nevus density in melanoma-prone families. An autosomal dominant mode of inheritance for DN has been proposed, and evidence suggests that DN may be a pleiotropic manifestation of the 1p36 familial melanoma gene. Several studies have shown a surprisingly high prevalence of DN on the skin of family members of probands with DN. In light of the extensive evidence documenting that persons with DN (both sporadic and familial) have an increased prospective risk for melanoma, these family studies suggest that relatives of persons with DN should be examined for DN and for melanoma. Overall, genetic determinants have a major role in the pathogenesis of normal nevi, DN, and melanoma. Elucidating the molecular basis of these genetic events promises to enhance melanoma risk reduction strategies and thereby reduce melanoma-associated mortality.