Sclerosing nevus with pseudomelanomatous features

PRAME-negativity in sclerosing nevi with pseudomelanomatous features supports classification as an indolent lesion

BACKGROUND

Some dysplastic nevi, termed sclerosing nevi with pseudomelanomatous features, may have florid fibroplasia associated with features that cause melanoma to be a prominent consideration in the differential diagnosis. PRAME (PReferentially expressed Antigen in MElanoma) immunohistochemistry (IHC) has been shown to be a useful marker in the distinction of melanoma and nevus. PRAME expression in such sclerosing nevi with pseudomelanomatous features has not been evaluated to our knowledge.

METHODS

Thirty-two sclerosing nevi with pseudomelanomatous features were stained with PRAME IHC, with positive labeling defined as staining of >75% of the cytomorphologically atypical lesional cells.

RESULTS

All 32 cases had variable cytologic atypia, bridging of elongated rete, fibroplasia, and a vertically oriented trizonal appearance. Some cases (23/32) had centrally located flattening of the rete ridge pattern bilaterally flanked by fibroplasia associated with elongated rete. PRAME labeling was negative (<1% labeling) in 28/32 cases. Four cases, also interpreted as having negative labeling with PRAME, showed only weak nuclear positivity of <50% of the melanocytes within the pseudomelanomatous foci. p16 staining was positive in 28/28 lesions.

CONCLUSIONS

Rare sclerosing nevi with pseudomelanomatous features (4/32; ~13%) had weak PRAME labeling of 25%-50% of atypical foci. Twenty-eight of 32 lesions had virtually no labeling with PRAME. PRAME results support classifying sclerosing nevi with pseudomelanomatous features as indolent lesions.

The WHO 2018 Classification of Cutaneous Melanocytic Neoplasms: Suggestions From Routine Practice

The "multidimensional" World Health Organization (WHO) classification 2018 of melanocytic tumors encompasses nine melanoma pathways (seven of which for cutaneous melanoma) according to a progression model in which morphologically intermediate melanocytic tumors are cosidered as simulators and/or precursors to melanoma. These "intermediates" can be subclassified into: i) a "classical" subgroup (superficial/thin compound: dysplastic nevus), which is placed within the morphologic and molecular progression spectrum of classical (Clark's and McGovern's) melanoma subtypes (superficial spreading and, possibly, nodular); and ii) a "non-classical" subgroup (thick compound/dermal: "melanocytomas") whose genetic pathways diverge from classical melanoma subtypes. Such a progression model is aimed at giving a conceptual framework for a histopathological classification; however, routine clinicopathological practice strongly suggests that most melanomas arise de novo and that the vast majority of nevi are clinically stable or even involuting over time. Clinicopathological correlation can help identify some severely atypical but benign tumors (e.g.: sclerosing nevus with pseudomelanomatous features) as well as some deceptively bland melanomas (e.g.: lentiginous melanoma; nested melanoma), thereby addressing some ambiguous cases to a correct clinical management. The recently available adjuvant therapy regimens for melanoma raise the problem of a careful distinction between severely atypical (high grade) melanocytoma and "classical" melanoma: conventional morphology can guide an algorithmic approach based on an antibody panel (anti-mutated BRAF, BAP1, PRAME, ALK, TRKA, MET, HRAS-WT, ROS; beta catenin; R1alpha; p16; HMB45; Ki67), a first-line molecular study (identification of hot spot mutations of BRAF and NRAS) and an advanced molecular study (sequencing of NF1, KIT, BRAF, MAP2K1, GNAQ, GNA11, PLCB4, CYSLTR2, HRAS; fusions studies of BRAF, RET, MAP3K8, PRKCA); as a final step, next-generation sequencing can identify melanocytic tumors with rare genetic signatures and melanocytic tumors with a high tumor mutation burden which should be definitely ascribed to the category of classical melanoma with the respective therapeutic options.

Sclerosing nevus with pseudomelanomatous features: dermoscopic and confocal aspects

BACKGROUND

Sclerosing nevus with pseudomelanomatous features (SNPFs) is a clinical and pathologic entity that mimics melanoma both clinically and histologically. The lesion is a melanocytic nevus, histologically characterized by fibrosis and a pseudomelanomatous proliferation. It is typically seen in young to middle-aged individuals, mainly on the back, where microtrauma or inflammatory changes are more frequent. Dermoscopic description of SNPF has been reported so far in one case series.

OBJECTIVE

The aim of our study was to describe the dermoscopic and confocal features of SNPF.

METHODS

Histopathologically confirmed cases of SNPF were retrospectively collected from three referral centres in Italy. Only lesions with available clinical, dermoscopic and histopathological data were included; confocal images were also retrieved, when available. Lesions were evaluated for the presence of 12 dermoscopic and five confocal criteria previously described.

RESULTS

The study population included 93 lesions in as many patients (71 men and 22 women; median age: 38 years). Dermoscopically, we found a predominance of dark colours, in particular brown and blue, which were found in all lesions and the vast majority of the lesions (86/93; 92.5%) displayed at least one structureless area. By the combination of colours and structures, we observed that the majority of the lesions (67/92; 72%) were characterized by more than one structure and more than one colour. Confocal evaluation was performed on a subset of 24/93 lesions showing a regular architecture pattern (19/24 cases, 79%), with a predominance of the ringed pattern. The presence of focal cytologic atypia at the dermal-epidermal junction was present in 12/24 cases (50%) with a prevalent dendritic-shaped cell proliferation.

CONCLUSIONS

The current study demonstrated that SNPF was frequently characterized, on dermoscopic examination, by more than one structure and more than one colour and on confocal microscopy by a regular ringed pattern with focal dendritic atypical cells.

A Practical Approach to the Diagnosis of Melanocytic Lesions

CONTEXT.—

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

OBJECTIVE.—

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

DATA SOURCES.—

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

CONCLUSIONS.—

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

Sclerosing Melanocytic Lesions (sclerosing Melanomas with Nevoid Features and Sclerosing Nevi with Pseudomelanomatous Features) - An Analysis of 90 Lesions

Background

Sclerosing melanocytic lesions, which are characterized by either focal or diffuse sclerosis in the dermal component and atypical proliferation of predominantly nevoid melanocytes, remain poorly defined. Our aim was to analyze systematically their morphologic spectrum, especially the distinction between sclerosing melanocytic nevus and sclerosing melanoma, which has not been well documented.

Patients and methods

We collected 90 sclerosing melanocytic lesions, occurring in 82 patients (49 male, 33 female; age range from 21 to 89 years). A four probe fluorescent in situ hybridization (FISH) assay was performed in 41 lesions to substantiate the diagnosis of sclerosing melanomas.

Results

A prominent full-thickness pagetoid spread of melanocytes was identified in 44 (48%) lesions, and a melanoma in situ adjacent to the sclerosis in 55 (61%) lesions. In the intrasclerotic component, maturation was absent in 40 (44%) and mitotic figures were identified in 18 (20%) lesions. Of the 90 lesions, 26 (29%) were diagnosed morphologically as nevi and 64 (71%) as melanomas (Breslow thickness from 0.4 to 1.8 mm), including 45 (50%) melanomas with an adjacent nevus. A four-probe FISH assay was positive in the sclerotic component in 14 of 25 lesions diagnosed morphologically as melanomas and none of 16 nevi. A sentinel lymph node biopsy was performed for 17 lesions and was negative in all cases.

Conclusions

Sclerosing melanocytic lesions form a morphologic spectrum and include both nevi and melanomas. The pathogenesis of sclerosis remains obscure but seems to be induced by melanocytes or an unusual host response in at least a subset of lesions.

Abundance of the benign melanocytic universe: Dermoscopic-histopathological correlation in nevi

The broad universe of "melanocytic nevi" includes a variety of different subtypes, which can be classified either due to their morphology, epidemiology, genetic alterations or risk for developing melanoma. Regarding morphology, on the one hand macroscopic/clinical and on the other hand histopathological appearance were used to subdivide in the past, often resulting in confusion and poor interobserver agreement, while nowadays dermoscopy presents the clinician's precious bridge between naked-eye examination and histopathological diagnostics, allowing prediction of the lesions' histopathology, follow up and monitoring over time without need of excision. The non-invasive dermoscopic examination relies on the assessment of colors, patterns and the distribution of both within a cutaneous lesion. Until today, the correspondence of certain dermoscopic colors and patterns to certain histopathological correlates has been reported for a huge amount of different cutaneous lesions. Moreover, the correspondence of certain dermoscopic features to certain body sites, age groups and pigmentary traits, but also to specific genetic alterations in lesions, has been broadly investigated. Dermoscopy has led us to a new understanding of melanocytic nevi's biology and evolution and, last but not least, to a new classification system, which we want to present herein.

Reflectance confocal microscopy analysis of equivocal melanocytic lesions with severe regression

BACKGROUND

The differential diagnosis between regressing nevi and melanoma might be challenging; regressing areas can represent a confounding factor for the diagnosis and the histology still remain mandatory to rule out melanoma. Reflectance confocal microscopy may add valuable information by revealing features suggestive of the nature of the melanocytic proliferation.

OBJECTIVE

To assess the impact of confocal microscopy in the management of regressive melanocytic lesions.

METHODS

The dermoscopic analysis of 92 melanocytic lesions showing that more than 30% of regressions have been retrospectively considered, among them, 32 melanocytic lesions with a 7 check point list ≥3 they were assessed at the rcm and subsequently excised. For each selected lesion, dermoscopic features of regression (white scar-like areas, blue areas, blue white areas), distribution of regressing areas (central, peripheral, or both) and the percentage of regression have been examined by an expert in dermoscopy, blinded to the histological and confocal diagnosis. Subsequently, two experts in confocal microscopy revaluated, blinded from histology, RCM images.

RESULTS

Of the 32 lesions analyzed, 23 (71.5%) were diagnosed histologically as nevi, and 9 (28.5%) as melanomas. 26 of 32 lesions (81.5%) exhibited regression >50% of the overall. On RCM, 11 lesions have been interpreted as malignant and 21 as benign. On RCM the majority of nevi exhibited regular architecture without cytological atypia. Epidermal disarray, pagetoid infiltration, disarranged dermo-epidermal junction architecture and atypical nests were considered as suspicious for malignancy. Good concordance between confocal readers has been detected.

CONCLUSION

A combined dermoscopic/confocal approach can be used for the management of lesions exhibiting dermoscopic features of regression in order to provide a more conclusive pre-histological diagnosis avoiding a high number of unnecessary excisions. Limits of this study were represented by the relatively small number of lesions and the retrospective approach. Further, prospective studies on a larger number of cases, will be necessary in order to compare the efficacy of dermoscopy alone versus dermoscopy in combination with RCM for the evaluation of regression, suspected pigmented lesions.

A risk scoring system for the differentiation between melanoma with regression and regressing nevi

BACKGROUND

Spontaneous regression of melanomas is relatively common, its prevalence ranging from 10 to 35%. However, regressing nevi can exhibit worrisome feature and simulate melanoma both clinically and dermoscopically. Thus, the presence of regression can represent a confounding factor.

OBJECTIVE

To investigate the frequency of dermoscopic patterns of "regression" in a series of benign and malignant melanocytic skin lesions, and to design an integrated scoring system. Scoring classifiers are very effective in selecting the significant parameters for discriminating two clinical conditions, thus can rapidly calculate a patient's risk for a given disease.

METHODS

We selected a series of 95 regressing melanocytic lesions, including 50 regressing nevi and 45 melanomas with regression. For each lesion, 12 dermoscopic variables (i.e. five types of regression structures, five atypical pigmentation structures, atypical vascular pattern and pink areas) were examined by three expert in dermoscopy (blinded to the histological diagnosis). The dermoscopic evaluation was then combined with patient age, gender, body site and the maximum diameter of lesion. Concordance analysis with Cohen's kappa was performed between the three clinicians. A risk scoring system was designed by the leave-one-out cross-validation procedure to ensure model prediction power.

RESULTS

The predictive score model revealed a sensitivity of 97.8% and a specificity of 75.5% in discriminating nevi and melanomas with regression. Using the score model, the diagnostic performance of the examiners increased by an average of 23.7% in sensitivity and 5.9% in specificity, compared with standard dermoscopic pattern analysis.

CONCLUSIONS

We assessed the validity of an integrated risk scoring model as a new methodological approach that could help the dermatologist in the differentiation between melanoma with regression and regressing nevus. Future studies could test the setting up of a score model over an even more complex pool of data obtained from different skin lesions with various diagnostic devices.

The Impact of Molecular Morphology Techniques on the Expert Diagnosis in Melanocytic Skin Neoplasms

Thirteen melanocytic skin neoplasms with a consultation diagnosis by A. Bernard Ackerman were submitted to immunohistochemistry for HMB-45, Ki67, cyclin D1, e-cadherin, and p16; 9/13 cases underwent fluorescence in situ hybridization (FISH) test targeting 6p25 (RREB1), 6q23 (MYB), centromere 6 (Cep6), and 11q13 (CCND1), as well as the centromere 7 (Cep7). A “consensus diagnosis” among 3 experts was also advocated both before and after morphomolecular information. Three neoplasms with a consultation diagnosis of Spitz nevus showed at least 3 abnormal immunohistochemical patterns; 2 of these cases were also FISH-positive for CCND1 gain, but none of them had a final consensus diagnosis of melanoma. Two neoplasms with a consultation diagnosis of congenital nevus received a consensus diagnosis of melanoma. Molecular morphology techniques can highlight the atypical features of melanocytic neoplasms and support existence of a morphobiologic “spectrum”: This should be mirrored in the final report by abandoning the dichotomic (benign vs malignant) diagnostic approach.

Clinico-pathological impact of fibroplasia in melanocytic nevi: a critical revision of 209 cases

Fibroplasia is a peculiar stromal reaction at the base of melanocytic lesions, particularly observed in so-called dysplastic nevi. This study evaluates a series of clinico-pathological features in nevi with fibroplasia, their frequence in comparison to usual nevi, and the association of fibroplasia with the risk for the development of melanoma. A total of 209 consecutive nevi showing fibroplasia, belonging to 203 patients, was reviewed. Nevi with fibroplasia were more frequent in men, about half of the lesions belonged to patients aged 11-40 years, and the highest number (52%) were located on the posterior trunk. Lesions 6 mm or greater were 152 (72.73%). Junctional and compound nevi were 52 (24.8%), and 157 (75.2%), respectively. Inflammatory infiltrate was present in 67.8% of cases, melanophages in 56.4%, a lentiginous pattern in 31.1%, focal pagetoid infiltration in three lesions. Nevi with fibroplasia constituted 4.27% of all junctional and compound nevi diagnosed in the same period. A total of 23 patients (11.3%) had a personal history of melanoma. The total number of nevi excised from the 203 patients ranged between 1 and 21, and significantly correlated with the patient's personal history of melanoma (p < 0.001). Fibroplasia is relatively infrequent in melanocytic nevi, it does not appear related to a process of senescence of the lesion, and does not represent a particularly strong predictor of risk of melanoma.

[Complete regression of melanocytic nevi: correlation between clinical, dermoscopic, and histopathologic findings in 13 patients]

BACKGROUND

The complete regression of melanocytic tumors, confirmed by histology, has rarely been reported in the literature. It is very difficult to determine the malignant or benign nature of a regressed tumor, and on occasions, the only indication of malignancy is the subsequent development of metastasis.

MATERIAL AND METHODS

We performed a descriptive study of melanocytic nevi that had undergone complete, histologically confirmed regression prior to excision in the dermatology department of our hospital over a period of 3 years. We included only lesions in which dermoscopy performed prior to regression showed features that suggested benignity. We assessed various clinical, dermoscopic, histologic, and immunohistochemical features.

RESULTS

The mean time to complete regression was 6.4 months. The main dermoscopic patterns observed were reticular and mixed reticular/globular. Unlike what is generally seen in melanomas, the main histologic finding was the presence of fine or lamellar fibrosis. In all cases, there was a predominance of CD8+ T cells.

CONCLUSIONS

The clinical, dermoscopic, and histologic features of the melanocytic nevi studied suggest the existence of a highly characteristic form of tumor regression characterized by very rapid regression and the involvement of a cytotoxic mechanism.

The recurrent nevus phenomenon: a history of challenge, controversy, and discovery

CONTEXT

The diagnosis of recurrent nevus poses a potential challenge to practicing pathologists. Although most recurrent nevi show uniform microscopic findings and pose no great diagnostic difficulty, a few cases exhibit some histopathologic features similar to, and in some cases indistinguishable from, melanoma. Historically, the term pseudomelanoma has been used in the literature to describe such recurrent nevi, although this label has the potential for confusion and is no longer the favored term for recurrent pigmented melanocytic nevi.

OBJECTIVE

To describe historical, histopathologic, and immunohistochemical features of recurrent pigmented melanocytic nevi and to review briefly the literature surrounding the mechanism of recurrence.

DATA SOURCES

Published peer-reviewed literature and the authors' personal experience.

CONCLUSIONS

Recognition of the histopathologic pattern of recurrent nevi leads the pathologist to the correct diagnosis in most cases; however, in particularly challenging specimens or in circumstances in which there is insufficient clinical history, immunohistochemical studies have proved helpful in distinguishing recurrent nevi from melanoma.

Congenital melanocytic nevi

This article reviews congenital melanocytic nevi (CMN), which are present at birth or appear shortly thereafter, and their main histologic features. Several histologic variants and histopathologic criteria that differentiate CMN from other nevi, such as atypical or dysplastic nevi, and from nevoid malignant melanoma, are discussed. Histologic pitfalls in the correct identification of lentiginous melanocytic hyperplasia, pagetoid scatter, and proliferative nodules in the context of CMN are discussed. The risk for development of malignant melanoma in association with a congenital melanocytic nevus and variable causes for changing mole are discussed.

Congenital Melanocytic Nevi

This article reviews congenital melanocytic nevi (CMN), which are present at birth or appear shortly thereafter, and their main histologic features. Several histologic variants and histopathologic criteria that differentiate CMN from other nevi, such as atypical or dysplastic nevi, and from nevoid malignant melanoma, are discussed. Histologic pitfalls in the correct identification of lentiginous melanocytic hyperplasia, pagetoid scatter, and proliferative nodules in the context of CMN are discussed. The risk for development of malignant melanoma in association with a congenital melanocytic nevus and variable causes for changing mole are discussed.