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

Clinical features and management of eyelid margin nevi

PURPOSE

Acquired melanocytic nevi are common eyelid lesions; however, their clinical presentation is not well documented.

METHODS

In this retrospective study, clinical records were reviewed in patients evaluated between 2005 and 2022.

RESULTS

Eyelid margin nevi (n = 150) were more commonly excised in female (78%) and Caucasian (86%) patients. Change in appearance/size were frequent presenting complaints, and 17% experienced ocular symptoms. Referring diagnosis included other benign lesions (11.3%), and concern for malignancy (16.7%). Many individuals (38.7%) noted their lesion for ≤5 years. Nevi were distributed across the 4 margins (9% peripunctal), and 88% had a regular base. Visible pigmentation was more common in non-Caucasians (95.2%) than Caucasians (41.1%). Lashes grew through 60.7% of nevi and were often misdirected.Nevi were treated with superficial excision and cauterization. Histologic subtypes included: dermal (86.6%), compound (9.4%), blue (2.7%), junctional (0.7%), lentiginous dysplastic (0.7%). An irregular base (p=0.042) and pigmentation (p=0.056) were more common in compound than dermal nevi. Lash line quality and appearance were improved in the majority of patients returning for follow-up, although postoperative trichiasis, marginal erythema, and residual pigmentation were observed.

CONCLUSIONS

Melanocytic nevi commonly involve the eyelid margins and have a variety of presentations and appearances. Existing nevi can change, and new lesions appear throughout adulthood. Stable, benign appearing nevi can be observed. Shave excision provides a diagnosis and improved appearance for symptomatic or suspicious lesions, with few serious complications. Malignant transformation is rare, although evidence for recurrence warrants further evaluation.

Recurrent Nevus Phenomenon Developing within a Keloid

The recurrent nevus phenomenon represents the persistence of a nevus within a scar from a prior biopsy site, with the acquisition of clinical and histologic features frequently overlapping with those of melanoma, posing relevant diagnostic challenges. Similar features are recognized in nevi that have undergone recent or chronic trauma and in sclerosing nevi. Any type of nevus may be subject to this phenomenon. Keloids are exuberant scars with an exaggerated accumulation of dense dermal collagen. Here we report a case of a 42-year-old woman with the incidental finding of an atypical melanocytic proliferation developing within a keloidal scar. The patient presented with a progressively enlarging auricular lesion three years after a piercing procedure. Upon histological examination, attentive scrutiny of the margin revealed an atypical compound melanocytic proliferation, predominantly single-celled at the junction but occasionally nested, with cytologic atypia and architectural disorder. This atypical proliferation was found emerging above a keloid. We interpreted the lesion as an atypical melanocytic lesion with features resembling the recurrent nevus phenomenon. This case raises awareness in recognizing these melanocytic lesions as benign, thereby avoiding overdiagnosis and unnecessary treatment.

Inactivation of the Hippo tumor suppressor pathway promotes melanoma

Melanoma is commonly driven by activating mutations in the MAP kinase BRAF; however, oncogenic BRAF alone is insufficient to promote melanomagenesis. Instead, its expression induces a transient proliferative burst that ultimately ceases with the development of benign nevi comprised of growth-arrested melanocytes. The tumor suppressive mechanisms that restrain nevus melanocyte proliferation remain poorly understood. Here we utilize cell and murine models to demonstrate that oncogenic BRAF leads to activation of the Hippo tumor suppressor pathway, both in melanocytes in vitro and nevus melanocytes in vivo. Mechanistically, we show that oncogenic BRAF promotes both ERK-dependent alterations in the actin cytoskeleton and whole-genome doubling events, which independently reduce RhoA activity to promote Hippo activation. We also demonstrate that functional impairment of the Hippo pathway enables oncogenic BRAF-expressing melanocytes to bypass nevus formation and rapidly form melanomas. Our data reveal that the Hippo pathway enforces the stable arrest of nevus melanocytes and represents a critical barrier to melanoma development.

Activating mutations of BRAF alone are inadequate to drive melanoma formation. Here the authors show that activation of Hippo signalling by oncogenic BRAF represents an additional safeguard to limit BRAF-dependent human melanocyte growth and melanoma formation.

Recognizing Histopathological Simulators of Melanoma to Avoid Misdiagnosis

Melanocytic lesions have a wide morphological spectrum, ranging from benign nevi to malignant melanoma. In contrast to a diagnosis of a benign nevus, a diagnosis of melanoma could mean intensive treatment, lifetime monitoring, and a worse prognosis. Therefore, melanocytic tumors are notoriously challenging and associated with a high risk of litigation in surgical pathology. After describing the basic features of nevi and melanoma, this article describes the detailed clinical and histological features of those lesions that share many similar features with melanoma. The entities included are Spitz nevi and atypical Spitz tumors (AST), Reed nevus, dysplastic nevus, cellular blue nevus (CBN), deep penetrating nevus, combined nevus, recurrent nevus, irritated nevus, congenital pattern nevus, acral nevus, and nevi of special sites. Knowledge of these imitators can help pathologists distinguish between benign and malignant cases and avoid misdiagnosis.

Dermoscopic Aspects of Traumatized Nevi After Dermabrasion

BACKGROUND

Melanocytic nevi submitted to trauma can undergo clinical, dermoscopic, and even histological changes, making it difficult to differentiate them from a melanoma.

OBJECTIVE

The aim of this study is to evaluate the dermoscopic changes of traumatized nevi after dermabrasion.

METHODS

Dermoscopic images of acquired melanocytic nevi were compared before and 4 weeks after half of their area had undergone dermabrasion.

RESULTS

The sample consisted of 50 lesions from 15 patients. The homogeneous pattern was the most frequent, followed by the reticular, cobblestone, and globular patterns. After dermabrasion, nearly half of the lesions (46%) became dermatoscopically asymmetric. Among all lesions, structureless areas, dotted vessels and erythema were the most frequent new dermoscopic structures.

CONCLUSION

Trauma after dermabrasion may induce significant dermoscopic changes in melanocytic nevi. Although the global pattern did not change, most of the lesions became asymmetric, with the appearance or fading of dermoscopic structures and colors. A history of recent trauma should be investigated when evaluating pigmented lesions.

Non-invasive optical biopsy by multiphoton microscopy identifies the live morphology of common melanocytic nevi

Multiphoton microscopy (MPM) is a promising non-invasive imaging tool for discriminating benign nevi from melanoma. In this study, we establish a MPM morphologic catalogue of common nevi, information that will be critical in devising strategies to distinguish them from nevi that are evolving to melanoma that may present with more subtle signs of malignancy. Thirty common melanocytic nevi were imaged in vivo using MPM. Quantitative parameters that can distinguish between different types of nevi were developed and confirmed by examining the histology of eleven of the imaged nevi. MPM features of nevi examined included cytologic morphology of melanocytes in the epidermis and dermis, the size and distribution of nevomelanocytes both within and around nests, the size of rete ridges, and the presence of immune cells in the dermis. Distinguishing features include cytological morphology, the size of nevomelanocytes, the size of nevomelanocyte nests, and the distribution of nevomelanocytes. Notably, these distinguishing characteristics were not easily appreciated in fixed tissues, highlighting essential differences in the morphology of live skin. Taken together, this work provides a morphologic compendium of normal nevi, information that will be critical in future studies directed at identifying melanocytic nevi that are evolving to melanoma.

Polypoid Compound Melanocytic Proliferations: A Clinicopathological Study

Nevi can show a polypoid appearance both clinically and histologically. Anecdotally, polypoid compound melanocytic nevus may exhibit a spectrum of junctional architectural and cytologic atypia, at times creating a diagnostic challenge by mimicking the radial growth phase of melanoma. To investigate this issue, we prospectively reviewed 40 polypoid compound melanocytic proliferations without overt malignant features. The lesions frequently occurred in young female patients and were predominantly from the trunk and intertriginous areas. Commonly observed atypical features included asymmetry (30%), shouldering (47.5%), poor circumscription (37.5%), and deep extension of melanocytes along the adnexal structures (67.5%). Severe cytologic junctional atypia (22.5%), dermal mitoses (10%), and pagetoid spread of melanocytes (5%) were less commonly seen. All lesions showed a reassuring dermal component with negligible cytologic atypia and maturation with depth. Overall, 7 lesions could not be readily classified as benign nevus; 5 of these in which a benign diagnosis was strongly favored were classified as atypical polypoid compound melanocytic nevi, whereas 2 lesions with diffuse severe junctional cytologic atypia and dermal mitoses were classified as ambiguous melanocytic proliferations. Atypical/ambiguous lesions were significantly larger and predominantly located in the axilla and groin. On molecular studies, none of the lesions tested showed the molecular profile of melanoma. We confirmed that polypoid compound melanocytic nevus can exhibit a variable degree of junctional atypia, likely related to frequent episodes of trauma and regeneration resulting in melanocytic proliferation. Pathologists should be aware of this phenomenon to avoid overdiagnosis.

Histologic mimics of malignant melanoma

Although spongiotic (eczematous), psoriatic and cutaneous skin infections are among the most common in dermatology consultations, melanocytic lesions - including the different types of nevi and melanomas - are among those that cause a great deal of concern and stress to patients and their clinicians. A diagnosis of benign melanocytic nevus carries a very good prognosis. However, a diagnosis of melanoma might indicate more aggressive treatment, lifelong surveillance and a worse prognosis. Differentiating between these conditions is not always a straightforward process for clinicians and pathologists. Therefore, knowledge of melanoma mimickers is very important for clinicians in general, and dermatologists and pathologists in particular. In this review, we called attention to some of the more frequent benign but unusual melanocytic lesions that are of diagnostic concern for clinicians evaluating these cutaneous proliferations.

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.

[Recurrent nevus: Case-report about a pagetoid form occurring from a congenital nevus in infancy]

INTRODUCTION

Recurrent nevus (RN) is a cutaneous benign tumour with similarities with malignant lesions. Typically, it occurs after a partial resection of commun-acquired nevus. Its incidence varies from 0.3 to 27% according to the studies. We present here a pediatric case of a pagetoid form of a recurrent nevus occurring from a congenital nevus.

CASE REPORT

A congenital nevus was removed from a 9-month-old girl. Pathologists concluded to a commun-acquired nevus of complete exeresis. Two other cutaneous lesions appeared and we decided to realise a total removal. Analysis showed a recurrent nevus with some atypical histological features. No recurrence has occurred during the three post-operative of follow-up.

DISCUSSION

It is an interesting case because of the occurrence of a RN after the removal of a congenital nevus in a child. Furthermore, it displayed some atypical histological features. Practicians, such as surgeons, dermatologists or pathologists, have to be aware of the risk of misdiagnosis with this lesion, which presents some similarities with SSM melanoma. It would be interesting to determinate some markers to statuate about its benign feature. There is no management recommendation about this lesion but it seems to be necessary to remove it to eliminate a malignant tumour.

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.

The recurrent nevus phenomenon

Recurrent melanocytic nevus is a proliferation of melanocytes arising from a melanocytic nevus removed partially. Asymmetry and irregular pigmentation may lead to misdiagnosis of melanoma. We report a patient presented with a lesion on the lower abdomen, which was removed by shave excision. Anatomopathological examination revealed an intradermal melanocytic nevus. Two months later, a new irregular hyperpigmented lesion appeared in the surgical scar. Histopathology of the excisional biopsy revealed a recurrent melanocytic nevus. Recurrent melanocytic nevus manifests as a scar with hyper or hypopigmented areas, linear streaking, stippled pigmented halos, and/or diffuse pigmentation patterns. Histologically, the dermoepidermal junction and the superficial dermis show melanocytic proliferation overlying the scarred area. When a pathological report of the previous lesion is not available, complete excision is the gold standard. Otherwise, regular dermoscopic monitoring is a therapeutic option. The present report emphasizes the importance of histopathological examination of the excised material - even in cases of suspected benign lesions - and warns patients about the possibility of recurrence in case of incompletely removed lesions.

Melanocytic nevi and melanoma: unraveling a complex relationship

Approximately 33% of melanomas are derived directly from benign, melanocytic nevi. Despite this, the vast majority of melanocytic nevi, which typically form as a result of BRAF^V600E-activating mutations, will never progress to melanoma. Herein, we synthesize basic scientific insights and data from mouse models with common observations from clinical practice to comprehensively review melanocytic nevus biology. In particular, we focus on the mechanisms by which growth arrest is established after BRAF^V600E mutation. Means by which growth arrest can be overcome and how melanocytic nevi relate to melanoma are also considered. Finally, we present a new conceptual paradigm for understanding the growth arrest of melanocytic nevi in vivo termed stable clonal expansion. This review builds upon the canonical hypothesis of oncogene-induced senescence in growth arrest and tumor suppression in melanocytic nevi and melanoma.

Analysis of major elements in pigmented melanocytic chicken skin using laser-induced breakdown spectroscopy

The concentration difference of major elements in melanocytic skin with respect to pigmentation level is analysed by laser-induced breakdown spectroscopy (LIBS) to investigate the applicability of LIBS as an in situ feedback tool for selective and complete laser removal of melanocytic skin tissue like nevus. The skin of black silkie chicken which had a characteristic darkly pigmented perifollicular skin surrounded by lightly pigmented extrafollicular skin was used as the sample. The results showed higher LIBS signal intensities of Ca²⁺ and Mg²⁺ but lower intensities of Na⁺ , Cl^- and K⁺ in the perifollicular skin than in the extrafollicular skin, which demonstrated the feasibility to use LIBS as a reliable method to distinguish skin tissues with difference in pigmentation level. Plasma emission of biochemical elements generated with a laser irradiation on melanocytic skin lesion.

Recurrence of Dysplastic Nevi Is Strongly Associated with Extension of the Lesions to the Lateral Margins and into the Deep Margins through the Hair Follicles in the Original Shave Removal Specimens

Melanocytic nevi, including dysplastic or atypical nevi (DN), can recur or persist following shave removal procedures, and recurrence may resemble melanoma, both clinically and histologically (pseudomelanoma). Recurrence may originate from proliferation of the remaining neoplastic melanocytes following incomplete removal. The present study determines the rate and etiology of this event. A cross-sectional analysis of 110 excision specimens showing histological recurrence was performed, and these specimens were compared to the slides of the original shave specimens showing mildly atypical DN. In the second portion of the study, a retrospective review of 167 cases with biopsy-proven mildly atypical DN which were followed up for at least two years was conducted to determine the rate of recurrence/persistence. When followed up for two years, DN, with positive shave margins, defined by extension or very close extension (≤0.2 mm) of the lesions to the lateral margins and into the deep margins through the hair follicles in the shave removal specimens, have a higher probability of recurrence than DN with negative (or clear) margins (odds ratio (OR) = 158; 95% confidence interval (CI) = 36.62–683; P < 0.001). The overall rate of histologically confirmed recurrence/persistence was approximately 10%.

Selected benign cutaneous lesions that may simulate melanoma histologically

As cutaneous melanomas manifest a wide spectrum of clinical and pathologic presentations, several other lesions enter into their differential diagnosis. This article considers those entities, including melanocytic hyperplasia, cellular nodules in congenital nevi, atypical lentiginous melanocytic proliferations, "special site" nevi, epithelioid histiocytoma, neurothekeoma, cellular schwannoma, and proliferating scars.

The regenerating naevus

The re-emergence of a melanocytic proliferation at the site of a previously excised pigmented lesion may not only cause great concern clinically but may also be amongst the most difficult of all melanocytic lesions for pathologists to assess. These lesions can adopt an appearance which may be impossible to confidently distinguish from a regressing or traumatised melanoma on histological grounds alone. For this reason, careful attention must be paid to the clinical context which has given rise to the lesion or a misdiagnosis may occur. In the absence of a corroborating history of prior surgery or trauma to the site, a diagnosis of a regenerating naevus may only be provisional. When considering a diagnosis of regenerating naevus, whenever possible, it is important to review and confirm the benign nature of the precursor lesion. Nevertheless, 50 years of research into this phenomenon has identified certain characteristic clinical features and histological patterns which provide clues both to clinicians and pathologists that will assist them to make the correct diagnosis and avoid over diagnosing as melanoma what is ultimately a benign process.

A recurrent melanocytic nevus phenomenon in the setting of Hailey-Hailey disease

Atypical acquired melanocytic nevi in patients with epidermolysis bullosa (EB) have been referred to as EB nevi and are considered to be a type of recurrent nevus with atypical but distinctive histopathologic findings. Herein, we describe an atypical nevus in a patient with Hailey-Hailey disease with different histopathologic findings from EB nevi because of presumably different pathogenesis. It is important to be aware that the recurrent nevi phenomenon can be seen in acantholytic conditions as well as blistering disorders, given these lesions may clinically resemble melanoma.

Investigation of cAMP microdomains as a path to novel cancer diagnostics

Understanding of cAMP signaling has greatly improved over the past decade. The advent of live cell imaging techniques and more specific pharmacologic modulators has led to an improved understanding of the intricacies by which cAMP is able to modulate such a wide variety of cellular pathways. It is now appreciated that cAMP is able to activate multiple effector proteins at distinct areas in the cell leading to the activation of very different downstream targets. The investigation of signaling proteins in cancer is a common route to the development of diagnostic tools, prognostic tools, and/or therapeutic targets, and in this review we highlight how investigation of cAMP signaling microdomains driven by the soluble adenylyl cyclase in different cancers has led to the development of a novel cancer biomarker. Antibodies directed against the soluble adenylyl cyclase (sAC) are highly specific markers for melanoma especially for lentigo maligna melanoma and are being described as "second generation" cancer diagnostics, which are diagnostics that determine the 'state' of a cell and not just identify the cell type. Due to the wide presence of cAMP signaling pathways in cancer, we predict that further investigation of both sAC and other cAMP microdomains will lead to additional cancer biomarkers. This article is part of a Special Issue entitled: The role of soluble adenylyl cyclase in health and disease.

Epidermolysis bullosa nevus in a patient with recessive dystrophic epidermolysis bullosa: a case report

We present a case of a 6-year-old girl with recessive dystrophic epidermolysis bullosa (EB) who presented with a large pigmented lesion clinically concerning for melanoma. After histological examination and fluorescent in situ hybridization analysis, diagnosis of EB nevus was performed. EB nevi are benign melanocytic neoplasms with histological findings similar to recurrent nevi occurring in all types of EB. They often mimic melanoma clinically, dermatoscopically, and histopathologically. The ability to recognize an EB nevus is essential for appropriate management of the patient. Unnecessary surgical excision in patients with already high-risk EB should be avoided. Close monitoring of these lesions is recommended because no cases of transformation to melanoma have been described.

"Lentiginous melanoma": full-fledged melanoma or melanoma precursor?

On the basis of a critical review of published literature, it is concluded that there is as yet insufficient evidence to conclude that the melanocytic lesion, which is currently known as "lentiginous melanoma," is a full-fledged melanoma, with the capacity to metastasize to distant sites and to cause the demise of the patient. It is proposed that this lesion is better designated as "lentiginous SAMPUS," that is, a superficial atypical melanocytic proliferation of uncertain significance, with a lentiginous, or predominantly lentiginous, arrangement of the junctional component. As there is uncertainty regarding its actual metastatic potential or the likelihood of progression to melanoma NOS, the lesion should be removed completely, with free surgical margins.

Postexcisional melanocytic regrowth extending beyond the initial scar: a novel clinical sign of melanoma

BACKGROUND

Recurrent naevi are widely recognized to occur commonly following incomplete removal of melanocytic lesions. These lesions have been generally understood as representing benign imitators of melanoma.

OBJECTIVES

To provide a formal description of the clinical findings of postexcisional melanocytic regrowth.

METHODS

We examined all cases of recurrent pigmentation adjacent to scars from previous excisional biopsies of melanocytic naevi treated at a private dermatology practice from 1995 to 2012.

RESULTS

We report nine cases of recurrence of melanocytic lesions that were melanomas. The most suspicious clinical feature for melanoma in these cases was the growth of the lesion beyond the confines of the initial scar, into the surrounding normal skin.

CONCLUSIONS

This pattern of recurrence of a melanocytic lesion represents a little recognized and distinctive clinical presenting sign of melanoma.