Verrucous naevoid and keratotic malignant melanoma: a clinico-pathological study of 20 cases

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.

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.

Seborrheic keratosis-like melanoma: a diagnostic challenge

This article summarizes the main epidemiologic and diagnostic features of seborrheic keratosis-like (SK-like) melanoma. We performed a review of the current literature. The real and current incidence and prevalence of SK-like melanoma are unknown. Many lesions are misdiagnosed and not excised with histopathologic confirmation, or excised without an appropriate surgical approach due to a benign clinical and dermoscopic appearance. SK-like melanoma presents both melanoma and SK features. SK-like melanoma and SK are often clinically indistinguishable even for experienced dermatologists. Clinically, it develops as a black-dark brown or light slightly elevated, papule, nodule or plaque with rapid growth and a regular or irregular shape. SK-like melanoma presents melanocytic and nonmelanocytic dermoscopic features. Irregular dark-brown dots/globules, a blue-grayish veil, streaks, irregular pigmentation or network and brown lines point to a melanoma diagnosis. Among the nonmelanocytic features, milia-like cysts and comedo-like openings have been highlighted. The association of polarized and nonpolarized dermoscopic techniques is more accurate for studying the dermoscopic features of SK-like melanoma. If the dermoscopic features are unclear, further investigations with reflectance confocal microscopy (RCM) or biopsy with histologic examination are essential. SK-like melanoma is a dermatologic challenge. Careful clinical and dermoscopic evaluation favor a correct diagnosis. In unclear cases, it is important to perform a biopsy with histologic examination to confirm the correct diagnosis.

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.

Optimization of an automated tumor-infiltrating lymphocyte algorithm for improved prognostication in primary melanoma

Tumor-infiltrating lymphocytes (TIL) have potential prognostic value in melanoma and have been considered for inclusion in the American Joint Committee on Cancer (AJCC) staging criteria. However, interobserver discordance continues to prevent the adoption of TIL into clinical practice. Computational image analysis offers a solution to this obstacle, representing a methodological approach for reproducibly counting TIL. We sought to evaluate the ability of a TIL-quantifying machine learning algorithm to predict survival in primary melanoma. Digitized hematoxylin and eosin (H&E) slides from prospectively enrolled patients in the NYU melanoma database were scored for % TIL using machine learning and manually graded by pathologists using Clark's model. We evaluated the association of % TIL with recurrence-free survival (RFS) and overall survival (OS) using Cox proportional hazards modeling and concordance indices. Discordance between algorithmic and manual TIL quantification was assessed with McNemar's test and visually by an attending dermatopathologist. In total, 453 primary melanoma patients were scored using machine learning. Automated % TIL scoring significantly differentiated survival using an estimated cutoff of 16.6% TIL (log-rank P < 0.001 for RFS; P = 0.002 for OS). % TIL was associated with significantly longer RFS (adjusted HR = 0.92 [0.84-1.00] per 10% increase in % TIL) and OS (adjusted HR = 0.90 [0.83-0.99] per 10% increase in % TIL). In comparison, a subset of the cohort (n = 240) was graded for TIL by melanoma pathologists. However, TIL did not associate with RFS between groups (P > 0.05) when categorized as brisk, nonbrisk, or absent. A standardized and automated % TIL scoring algorithm can improve the prognostic impact of TIL. Incorporation of quantitative TIL scoring into the AJCC staging criteria should be considered.

Uncommon Histopathological Variants of Malignant Melanoma. Part 2

Despite new horizons opened by recent advances in molecular pathology, histological evaluation still remains the diagnostic gold standard regarding cutaneous melanocytic neoplasms. Several histological variants of melanoma have been described, and their knowledge is crucial for accurate diagnosis and classification of cases with unusual clinico-pathological features. Uncommon histological variants of melanoma have been described based on a broad constellation of features, including architectural pattern, stromal alterations, cytological attributes, and other morphological properties. This review is aimed at providing an extensive discussion of unusual but distinctive histopathological variants of melanoma.

Clinical spectrum of cutaneous melanoma morphology

BACKGROUND

Melanoma can mimic other cutaneous lesions, but the full spectrum and prevalence of these morphologic variants remain largely unknown.

OBJECTIVE

To classify nonacral cutaneous melanomas into distinct morphologic clusters and characterize clusters' clinicopathologic features.

METHODS

All pathologic melanoma diagnoses (occurring during 2011-2016) were reviewed for routine prebiopsy digital photographs (n = 400). Six dermatologists independently assigned lesions into 1 of 14 diagnostic classes on the basis of morphology. Image consensus clusters were generated by K-means; clinicopathologic features were compared with analysis of variance and χ².

RESULTS

Five morphologic clusters were identified: typical (n = 136), nevus-like (n = 81), amelanotic/nonmelanoma skin cancer (NMSC)-like (n = 70), seborrheic keratosis (SK)-like (n = 68), and lentigo/lentigo maligna (LM)-like (n = 45) melanomas. Nevus-like melanomas were found in younger patients. Nevus-like and lentigo/LM-like melanomas tended to be thinner and more likely identified on routine dermatologic examinations. NMSC-like melanomas were tender, thicker, more mitotically active, and associated with prior NMSC. Typical and SK-like melanomas had similar clinicopathologic features.

LIMITATIONS

Cluster subdivision yielded diminished sample sizes. Visual assignment was performed without clinical context.

CONCLUSION

When primary cutaneous melanomas were assigned into diagnostic groups and subjected to novel consensus clustering, recurrent morphologic patterns emerged. The spectrum of these morphologies was unexpectedly diverse, which might have implications for visual training and possibly clinical diagnosis.

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.

Verrucous-Keratotic Malignant Melanoma (VKMM)

We report a patient with a verrucous keratotic variant of melanoma visiting the policlinic of Medical Institute of Ministry of Interior (MVR-Sofia), Department of Dermatology and Dermatologic surgery, with a keratotic verrucous lesion, located on the right thigh, partially deeply pigmented at upper right quadrant. The lesion had appeared three years ago before her presentation in the policlinic, and it had gradually enlarged and become darker in the last twelve months. The surface of the lesion was covered with thick hyperkeratotic lobules. The histologic evaluation revealed verrucous melanoma with a tumour thickness of 3 mm and Clark Level IV and focal ulceration. The tumour was staged as stage IIB (T3bN0M0). Sentinel lymph node biopsy was planned. Verrucous-keratotic forms of malignant melanoma occur more commonly in women and favour the extremities, but may be found on any anatomic site. Seventy-one percent of this melanoma type are situated on the upper and lower extremities. Although two-thirds of these neoplasms can be can be histologically graded according to the classification of Clark, one-third of these melanomas with marked verrucous hyperplasia and hyperkeratosis of the epidermis do not fit into his classification. Histological classification of patients with a verrucous keratotic type of melanoma may sometimes be extremely difficult. The marked papilliferous architecture of these lesions made an assessment of Breslow depth difficult. The presented case highlights the clinical existence and features of such benign-looking melanomas. It is therefore important for surgical pathologists to recognise this unusual variant of malignant melanoma, as it may be confused both clinically and pathologically with benign lesions.

Dermoscopic Clues for Diagnosing Melanomas That Resemble Seborrheic Keratosis

Importance

Melanomas that clinically mimic seborrheic keratosis (SK) can delay diagnosis and adequate treatment. However, little is known about the value of dermoscopy in recognizing these difficult-to-diagnose melanomas.

Objective

To describe the dermoscopic features of SK-like melanomas to understand their clinical morphology.

Design, Setting, and Participants

This observational retrospective study used 134 clinical and dermoscopic images of histopathologically proven melanomas in 134 patients treated in 9 skin cancer centers in Spain, France, Italy, and Austria. Without knowledge that the definite diagnosis for all the lesions was melanoma, 2 dermoscopy-trained observers evaluated the clinical descriptions and 48 dermoscopic features (including all melanocytic and nonmelanocytic criteria) of all 134 images and classified each dermoscopically as SK or not SK. The total dermoscopy score and the 7-point checklist score were assessed. Images of the lesions and patient data were collected from July 15, 2013, through July 31, 2014.

Main Outcomes and Measures

Frequencies of specific morphologic patterns of (clinically and dermoscopically) SK-like melanomas, patient demographics, and interobserver agreement of criteria were evaluated.

Results

Of the 134 cases collected from 72 men and 61 women, all of whom were white and who had a mean (SD) age of 55.6 (17.5) years, 110 (82.1%) revealed dermoscopic features suggestive of melanoma, including pigment network (74 [55.2%]), blue-white veil (72 [53.7%]), globules and dots (68 [50.7%]), pseudopods or streaks (47 [35.1%]), and blue-black sign (43 [32.3%]). The remaining 24 cases (17.9%) were considered likely SKs, even by dermoscopy. Overall, lesions showed a scaly and hyperkeratotic surface (45 [33.6%]), yellowish keratin (42 [31.3%]), comedo-like openings (41 [30.5%]), and milia-like cysts (30 [22.4%]). The entire sample achieved a mean (SD) total dermoscopy score of 4.7 (1.6) and a 7-point checklist score of 4.4 (2.3), while dermoscopically SK-like melanomas achieved a total dermoscopy score of only 4.2 (1.3) and a 7-point checklist score of 2.0 (1.9), both in the range of benignity. The most helpful criteria in correctly diagnosing SK-like melanomas were the presence of blue-white veil, pseudopods or streaks, and pigment network. Multivariate analysis found only the blue-black sign to be significantly associated with a correct diagnosis, while hyperkeratosis and fissures and ridges were independent risk markers of dermoscopically SK-like melanomas.

Conclusions and Relevance

Seborrheic keratosis-like melanomas can be dermoscopically challenging, but the presence of the blue-black sign, pigment network, pseudopods or streaks, and/or blue-white veil, despite the presence of other SK features, allows the correct diagnosis of most of the difficult melanoma cases.

[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.

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.

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.

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.

Paratumoral epidermal hyperplasia: a novel prognostic factor in thick primary melanoma of the skin?

There is a lack of histopathological factors to sub-stratify prognosis in pT3/4 melanoma primaries. In the presented pilot study, the prognostic significance of different clinical and histopathological parameters was studied in thick primary melanoma taking paratumoral epidermal hyperplasia (PTEH) into consideration. Of 1632 melanoma patients in the melanoma register of the Martin Luther University Halle-Wittenberg in the years 1980 to 1987, 16 cases with tumor thickness (TT) of the primary > or = 3 mm, documented metastasis-free follow-up of 10+ years after primary therapy and available histologic sections were compared with an adequate recurrence control group (n = 62) by PTEH and standard prognostic parameters. PTEH was demonstrable in 15 of 16 patients of the metastasis-free group (PTEH penetration depth 1.42 +/- 0.82 mm/mean +/- SD) and 27 of 62 of controls (0.29 +/- 0.46 mm), P < or = 0.001. Of the standard prognostic parameters, TT, sex, location, and lack of nevus association also correlated with metastasis. In multivariate analysis, PTEH > or = 1 mm was the single independent parameter with the highest (negative) association to recurrence (odds ratio 52.3). Occurrence of PTEH might predict a more moderate course of disease in thick melanoma. Thus, it might become an easily determinable and effective tool to sub-stratify prognosis in thick primary melanoma of the skin. Further studies are necessary to prove these findings.

Unusual histological variants of cutaneous malignant melanoma with some clinical and possible prognostic correlations

Malignant melanoma is known for the wide range of histological patterns it can assume mimicking other malignant tumors. We present a review of most of the unusual histological variants of cutaneous melanoma and describe their immunohistochemical features, associate clinical findings, and possible behavior related to the histological subtype. In addition, we propose their classification into four groups corresponding to the (1) architectural patterns; (2) cytologic features; (3) stromal changes; and (4) the possible association of these findings (i.e. architectural + cytologic features). Although most of these unusual variants have the same prognosis as conventional melanomas, with Breslow thickness and ulceration, being the most important predictor of survival in clinical stage I, some of them have a peculiar biologic behavior that the clinicians and the dermatopathologists should know in order to give melanoma patients all educational information available.

Melanoma within the seborrheic keratosis

Seborrheic keratoses (SKs) are common benign nonmelanocytic epidermal tumors with characteristic clinical features, which are thought to allow a straightforward diagnosis in most situations. As a result, it is an accepted practice to destroy them without histopathologic confirmation. However, systematic reviews of histologic specimens reveal an erroneous clinical diagnosis or associated malignant tumors in a number of cases, including malignant melanomas. We describe a patient with a clinically typical-appearing SK, which was biopsied and histologically proven to be a malignant melanoma arising in the SK. Our report is a reminder that the reliability of clinical diagnosis of SKs needs to be questioned. In addition, a biopsy of SKs is not only warranted but necessary in order to identify a malignant melanoma that would otherwise be misdiagnosed or even completely missed.

Melanoma associated with pseudoepitheliomatous hyperplasia: a case series and investigation into the role of epidermal growth factor receptor

BACKGROUND

Pseudoepitheliomatous hyperplasia (PEH) is a reactive epithelial proliferation that occurs in response to underlying infectious, inflammatory, and neoplastic conditions. The histologic features of PEH may simulate squamous cell carcinoma and may obscure an underlying malignant process. The association of PEH with benign melanocytic nevi is well described in the literature. However, reports documenting the association of PEH with melanoma are rare.

METHODS

We examined the demographic and histologic features in 13 cases of melanoma in association with PEH. In addition, we evaluated the possible pathogenic role of epidermal growth factor receptor (EGFR) using immunohistochemical methods.

RESULTS

In each case, histologic examination revealed epidermal hyperplasia with irregular cords of well-differentiated epithelial cells extending into the dermis and infiltrating the melanoma. Although overlap existed, two patterns of epidermal hyperplasia were noted. The majority of cases (69%) exhibited acanthosis, hyperkeratosis, papillomatosis, and irregular infiltrating epithelial cords with squamous eddies. The remaining cases demonstrated basaloid acanthosis, laminated orthokeratosis, and horn cysts. EGFR immunohistochemical studies revealed strong staining within the basal layer of the epithelium, with no discernible difference between the hyperplastic epithelium overlying the melanoma cells and adjacent normal skin. Immunostaining among the melanoma cells was absent to weak in each of the cases. All cases exhibited intense EGFR immunoreactivity in macrophages underlying the epidermal lesions.

CONCLUSIONS

Melanoma is capable of presenting in a variety of histologic guises, including a pattern with PEH. The etiology of PEH, as rarely seen in conjunction with melanoma, unlikely involves EGFR and remains to be elucidated.

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

Nevoid melanoma is a rare variant of melanoma characterized by deceptive morphologic features reminiscent of a benign melanocytic nevus. Twenty (13 nodular, 7 verrucous) nevoid melanomas were reviewed with the goal of identifying the predominant architectural patterns, cytologic features, and prognostic indicators. Although at scanning magnification, many lesions showed a strong resemblance to banal compound or dermal nevi, careful inspection in all cases demonstrated subtle pleomorphism and impaired maturation with depth, invariably accompanied by multiple dermal mitoses. Four tumors recurred and three metastasized, with subsequent death of the patients. Follow-up information for a period of at least 3 years was available in eight cases. In this group, mortality was 37.5%, the metastasis rate was 37.5%, and the local recurrence rate was 75%, with an average tumor thickness of 2.5 mm. We conclude that nevoid melanoma may be distinguished from a benign melanocytic nevus by a high index of suspicion, a careful analysis of architecture, and attention to cytologic features. Our data and a review of the literature do not support the notion that nevoid melanoma has a better prognosis than ordinary melanoma.

Minimal deviation and/or naevoid melanoma: is recognition worthwhile? A clinicopathological study of nine cases

One to two per cent of primary cutaneous melanomas share clinical features with benign melanocytic and non-melanocytic skin lesions, and even at histology recognition of their malignant nature is problematic, mainly due to the lack of an intraepithelial component, their nodular aspect and the monotonous cell population throughout the lesion. These tumours were termed minimal deviation melanomas (MDMs) by Reed et al. and later naevoid melanomas by Schmoeckel et al. The name MDM suggests the concept of a more favourable outcome for these melanomas that do not (yet) show the typical features of fully evolved lesions able to metastasize, although naevoid melanomas seem to behave like 'common' melanomas. In a retrospective analysis of nine cases of MDM collected from our database and followed for a median duration of 112 months, we faced similar clinical and histological pitfalls and observed local recurrence following marginal resection. Wide excision, even of local recurrence, and therapeutic node dissection could nevertheless provide survival comparable at least to that predicted by mathematical models for patients who initially had optimal treatment.

Differentiation of common benign pigmented skin lesions from melanoma by high-resolution ultrasound

BACKGROUND

There are potential clinical benefits if non-invasive methods can be used to diagnose or exclude melanoma.

OBJECTIVES

We investigated high-resolution ultrasound (HRU) as a potential non-invasive diagnostic aid for pigmented skin lesions.

METHODS

Using a 20-MHz ultrasound B-scan imaging system interfaced to a computer, we assessed acoustic shadowing and entry echo line enhancement (EEE) for 29 basal cell papillomas (BCPs) and 25 melanomas. Acoustic shadowing was estimated by the dermal echogenicity ratio (DER), comparing mean echogenicity below the lesion with that of adjacent dermis. Histological features were scored independently.

RESULTS

DER < 3 correctly distinguished melanoma from BCP with 100% sensitivity and 79% specificity. Specificity increased to 93% if the presence of EEE was included as a discriminator. Shadowing correlated most significantly with histological extent of hyperkeratosis (P < 0.0001). Consequently, this method falsely identified non-keratotic acanthotic BCP (n = 3) as melanoma. Highly significant differences between benign naevi (n = 15) and melanomas (n = 24) were found. The SD of retrolesional echogenicity was higher for naevi than melanomas (P < 0.0001), but such an analysis was poorly specific for the diagnosis of melanoma (30%).

CONCLUSIONS

Overall, HRU has considerable potential as a high-performance screening tool to assist in the discrimination between BCP, but not benign naevi, and melanoma. In particular, it may be possible to exclude melanoma with 100% certainty in the differentiation of BCP from melanoma.

Small cell malignant melanoma: a variant of naevoid melanoma. Clinicopathological features and histological differential diagnosis

AIMS

To describe the clinical and histopathological features of a rare variant of naevoid melanoma, small cell melanoma, and discuss the histological differential diagnoses.

METHODS

The clinical and histological features of cases of malignant melanoma with the histological features of small (non-Merkel like) melanoma were reviewed and documented. In addition, five cases had available material for immunohistochemistry and this was performed using antibodies to the S100 protein and melan-A, and the HMB-45 antibody.

RESULTS

There were 15 cases of small cell melanoma from 14 (10 female, four male) patients, aged between 30 and 77 (mean, 48.6) years. The trunk was the most common location. In more than half the cases, the provisional diagnosis was melanoma/borderline lesion. All shared similar histological appearances of an intraepidermal component of in situ melanoma and a dermal component of nests of cells with hyperchromatic nuclei and scanty cytoplasm, usually in tightly packed nests. All components (junctional and intradermal) of the lesions investigated by immunohistochemistry were positive both for S100 protein and melan-A. All junctional components were positive with HMB-45, but with variable staining of the dermal components with this antibody.

CONCLUSIONS

Small cell malignant melanoma is postulated to be a distinct histopathological entity and a rare variant of naevoid melanoma. Such lesions can be difficult to interpret and easily missed at scanning magnification because the cells of the dermal component mimic benign naevus cells.

Problematic pigmented lesions: approach to diagnosis

A number of pigmented lesions are difficult to classify and raise the possibility of a melanoma diagnosis. Care should be exercised to exclude non-melanocytic lesions, and benign melanocytic entities, both of which can mimic melanoma histologically. In addition, the possibility of the lesion being a melanoma variant or epidermotropic metastasis should be considered. There will still be some cases that are difficult to resolve. These usually fall into one of three categories: atypical junctional melanocytic lesion versus early melanoma; naevus versus naevoid melanoma; and atypical Spitz, cellular blue, and deep penetrating naevi versus thick melanoma. These will pose problems even for experts. The atypical Spitz lesions are perhaps the most important category because they tend to be from younger individuals, the differential diagnosis is thick melanoma, and there is no single discriminating histological feature.

Recent developments in the pathology of melanocytic neoplasia

This article selectively discusses clinically relevant aspects of the pathology of cutaneous melanocytic neoplasms, from the literature of the past recent years. Topics include the changing role of immunohistochemistry in diagnosis, the controversies over dysplastic nevi, description of other specialized variants of melanocytic nevi, diagnosis of melanocytic neoplasms of acral skin, and melanoma occurring in childhood. Several variants of melanoma including desmoplastic and spindle-cell types, verrucous melanoma, epidermotropic melanoma, and melanoma of the female genitalia are reviewed. The issue of appropriate margins of resection for melanoma and the use of Mohs Micrographic surgery for this tumor are considered. Finally, a review of the sentinel node biopsy technique and of nodal nevi is presented.

Variants of melanoma

The current classification of malignant melanomas gives recognition to superficial spreading melanoma, lentigo maligna melanoma, acral lentiginous melanoma, and nodular types. In addition, neurotropic and desmoplastic types are recognized. The relativity inherent in the diagnosis of melanoma, provides the basis for the classification of melanomas on the basis of size. Lesions measuring 1 mm or less in vertical dimensions are unlikely to metastasize; they qualify as borderline melanocytic neoplasia of indeterminant malignant potential. The current classification has little relevancy to the category of variant nevi with the exceptions of malignant cellular blue nevus and melanoma arising in giant congenital nevi. A classification of variant melanomas as related to variant nevi is proposed. From a different perspective, a classification of melanomas with attention to nesting and cytological patterns in vertical growth is proposed: this alternate approach gives recognition to lesions that might otherwise be classified as "nevoid" melanomas. It also provides a default category for lesions that might otherwise be assigned to the Spitz nevus-like category. All of these tools for the manipulation of the real and virtual images of melanomas have been emphasized in the concept of minimal deviation melanoma.

Dermatopathologic variants of malignant melanoma

An appropriate biopsy is the pivotal procedure that facilitates accurate histopathologic diagnosis of a pigmented skin lesion. Excisional skin biopsy is the method of choice for removing a suspected malignant melanoma. More than 95% of malignant melanomas that involve the skin belong to one of the four most common clinicopathologic categories: superficial spreading, nodular, lentigo maligna, and acral lentiginous melanoma. A small but important group of cutaneous melanomas can be classified as unusual variants. Many of these unusual variants have a distinct histopathologic appearance; they include desmoplastic melanoma, neurotropic melanoma, pedunculated melanoma, metastatic melanoma, amelanotic melanoma, melanoma arising within a benign nevus, regressing ("invisible") melanoma, and balloon cell melanoma. Other lesions may simulate malignant melanoma histopathologically. Immunohistochemical stains, such as S-100 protein, vimentin, keratin, and HMB-45, are useful for distinguishing these lesions from true melanoma.

Cutaneous melanoma and atypical Spitz tumors in childhood

BACKGROUND

Malignant melanoma in childhood is rare. As a result, the biology and natural history of melanoma in this age group is still poorly understood. Although the majority of Spitz nevi are benign regardless of atypical features, a particular problem is the continued confusion of Spitz nevi with atypical features with melanoma and the lack of specific criteria for their distinction. The latter discrimination is perhaps not so difficult when Spitz nevi are minimally atypical; however, the greater the atypia, the more challenging is this discrimination.

METHODS

All cases of malignant melanoma referred to Children's Hospital (Boston, MA) and to one of the authors were examined during the period of 1959-1995. Criteria for inclusion in the study included: (1) age up to 15 years; (2) availability of microscopic slides; and (3) availability of demographic data.

RESULTS

There were 11 males and 12 females, ranging in age from 2 to 15 years (mean age, 9.4 years). Histopathologically, the 23 tumors were categorized into four subgroups: (1) small cell melanoma (5); (2) adult-like melanoma (6); (3) Spitz-like melanoma (3), and (4) atypical Spitz tumors (9). The small cell melanomas were notable for localization to the scalp, significant thickness, and fatal outcome. The adult-like melanomas resembled typical tumors occurring in adults. The one fatal Spitz-like melanoma was located on the neck of a 14-year-old male. Two tumors in this group metastasized to regional lymph nodes, but were not associated with further aggressive disease on follow-up despite treatment with surgical excision only. The atypical Spitz tumors were characterized by significant thickness and abnormal features including prominent cellularity and mitotic activity.

CONCLUSIONS

Anatomic site and cell type may be important prognostic factors in addition to tumor thickness for childhood melanoma, but these tumors require further study. In addition, the biologic potential of atypical Spitz tumors has not been characterized sufficiently.