Spitz's nevi with halo reaction: a histopathologic study of 17 cases

Amplification of Mutant NRAS in Melanocytic Tumors With Features of Spitz Tumors

NRAS activating mutations are prevalent in melanocytic neoplasia, occurring in a subset of common acquired melanocytic nevi and ∼30% of cutaneous melanomas. In this study, we described a cohort of 7 distinctive melanocytic tumors characterized by activating point mutations in codon 61 of NRAS with amplification of the mutant NRAS allele and shared clinicopathologic features. These tumors occurred predominantly in younger patients, with a median age of 20 years (range, 6-56 years). They presented as papules on the helix of the ear (4 cases) or extremities (3 cases). Microscopically, the tumors were cellular, relatively well-circumscribed, compound, or intradermal proliferations. The tumor cells often extended into the deep reticular dermis and involved the superficial subcutaneous fat in some cases. The melanocytes were epithelioid to spindled with moderate amounts of cytoplasm and conspicuous nucleoli. They were arranged in short plexiform fascicles, nests, and cords. Some cases had occasional pleomorphic and multinucleated melanocytes. Rare dermal mitotic figures were present in all cases. The dermis contained thick collagen bundles and minimal solar elastosis. Follow-up data were available for 5 patients, with a median period of 4.2 years (range, 1-9 years), during which no recurrences or metastases were reported. Our series highlights a clinicopathologically and molecularly distinctive subset of NRAS-mutated tumors with amplification of the mutant NRAS allele.

The Spectrum of Spitz Melanocytic Lesions: From Morphologic Diagnosis to Molecular Classification

Spitz tumors represent a distinct subtype of melanocytic lesions with characteristic histopathologic features, some of which are overlapping with melanoma. More common in the pediatric and younger population, they can be clinically suspected by recognizing specific patterns on dermatoscopic examination, and several subtypes have been described. We now classify these lesions into benign Spitz nevi, intermediate lesions identified as “atypical Spitz tumors” (or Spitz melanocytoma) and malignant Spitz melanoma. More recently a large body of work has uncovered the molecular underpinning of Spitz tumors, including mutations in the HRAS gene and several gene fusions involving several protein kinases. Here we present an overarching view of our current knowledge and understanding of Spitz tumors, detailing clinical, histopathological and molecular features characteristic of these lesions.

Immunophenotype of tumor-infiltrating lymphocytes in atypical Spitzoid tumors according to the risk of progression

The aims of the study were to investigate and compare the immunophenotype of tumor-infiltrating lymphocytes (TILs) and PD-L1 expression in a series of benign, intermediate and malignant Spitzoid lesions showing marked inflammatory lymphoid component, to find out its possible relation with the prognosis of these lesions. Six out of 97 Spitz nevus (SN) (6 %), five out of 26 atypical Spitz tumors (AST) (16 %) and seven out of 37 Spitzoid melanomas (SM) (19 %) showed diffuse, intense inflammatory component and were included in the study. The biological risk of the tumors was assessed in all AST through the melanoma 4 probe-FISH assay and the 9p21 locus exploration. TILs were quantitatively immunophenotyped using CD3, CD4, CD8, CD20, TIA1, FOXP3 and PD1 antibodies. PD-L1 was assessed in tumoral cells and inflammatory cells adjacent to the tumor. No significant differences of TILs immunophenotype were found between SN, AST and SM. However, the classification of tumors according to the biological risk showed that grouped SN plus low-risk AST had a significantly higher number of T-cells CD8+ and TIA-1+, as well as a lower CD4/CD8 relation and B- lymphocyte number than high-risk of progression tumors (grouped high-risk AST plus SM). Immunoregulatory T-cell markers PD1 and FOXP3 only correlated with each other and with PD-L1 expression. In conclusion, The TILs immunoprofile differences between low-risk and high-risk of progression Spitzoid tumors, especially regarding CD8 and the cytotoxic immune response, can add prognostic information about these challenging tumors and impact the clinical management of patients.

Aberrant expression of HMB45 and negative PRAME expression in halo nevi

BACKGROUND

Traditionally, most cutaneous nevi show a gradient of HMB45 (human melanoma black 45) and negative PRAME (preferentially expressed antigen in melanoma) immunostaining, while melanomas often show irregularly positive, diffusely positive or completely negative HMB45 expression, and PRAME immunopositivity. However, we have occasionally observed benign halo nevi with loss of HMB45 gradient, raising diagnostic consideration for melanoma. The purpose of this study was to elucidate the expression pattern of HMB45 and PRAME in nevi with the halo phenomenon (NHP).

METHODS

PRAME and HMB45 staining patterns in 20 cases of NHP and 16 cases of conventional nevi were evaluated using light microscopy. An HMB45 gradient was defined as immunopositivity in only superficial melanocytes. HMB45 aberrant expression consisted of superficial and deep immunopositivity.

RESULTS

Aberrant HMB45 expression was observed in 10 of 20 NHP (50%). A gradient of HMB45 staining was seen in most conventional nevi, with only one showing focal weak expression in the deep dermis (6.3%). All cases of NHP and conventional nevi showed essentially negative immunostaining by PRAME.

CONCLUSION

Aberrant HMB45 expression in NHP is not uncommon and may be a diagnostic pitfall. Negative PRAME immunostaining may be a reassuring finding to help differentiate halo nevus from malignant melanoma.

Integrative histopathological and immunophenotypical characterisation of the inflammatory microenvironment in spitzoid melanocytic neoplasms

AIMS

The role of inflammation in conventional cutaneous melanoma has been extensively studied, whereas only little is known about the inflammatory microenvironment and immunogenic properties of spitzoid melanocytic neoplasms. The composition of infiltrating immune cells and the architectural distribution of the inflammation, in particular, are still obscure. This is the first study, to our knowledge, to systematically characterise the inflammatory patterns and the leucocyte subsets in spitzoid melanocytic lesions.

METHODS AND RESULTS

We examined 79 spitzoid neoplasms including banal Spitz naevi (SN, n = 50), atypical Spitz tumours (AST, n = 17) and malignant Spitz tumours (MST, n = 12) using histopathological analysis and immunohistochemistry. Spitzoid melanocytic lesions showed a high frequency (67.1%, n = 53 of 79) of inflammation. Four inflammatory patterns were identified according to architectural composition, distribution and intensity of inflammation. The majority of the inflammatory infiltrate corresponded to CD3+ /CD8+ T lymphocytes (56.1%), followed by CD3+ /CD4+ T cells (35.7%) and CD68+ histiocytes (20.3%). CD3+ /TIA-1+ cytotoxic T lymphocytes constituted 3.7% of inflammatory cells. Rarely, CD3+ / granzyme B+ cytotoxic T lymphocytes (2.7%) and CD138+ plasma cells (0.5%) were detected in the infiltrating immune cells. There was no significant difference in the inflammatory cellular composition among the spitzoid melanocytic subgroups (SN versus AST versus MST).

CONCLUSION

Our findings demonstrate that Spitz tumours are highly immunogenic lesions. Inflammation with the presence of lymphocytic aggregates predominated in SN, but was not distinctive for this melanocytic category. A strong and intense inflammation was suggestive of an underlying malignancy. The infiltrating cytotoxic T lymphocyte subsets in Spitz tumours deserve further investigation in larger study cohorts to elucidate prognostic and immuno-oncological therapeutic relevance.

BAP1-inactivated melanocytic tumor with preserved BAP1 expression? Morphology to the rescue!

BAP1-inactivated melanocytic tumors typically present with distinctive histopathological changes and loss of nuclear BAP1 protein expression. Rare cases exhibit the typical morphology but with preserved expression of BAP1. In the current issue of Journal of Cutaneous Pathology, Linos et al. describe such a case and provide a comprehensive molecular-genetic exploration to explain such a phenomenon.

New and evolving concepts of melanocytic nevi and melanocytomas

In daily clinical practice melanocytic nevi are commonly encountered. Traditionally, both benign and malignant melanocytic tumors have been sub-classified by their histopathologic characteristics with differing criteria for malignancy applied to each group. Recently, many of the mutations that initiate nevus formation have been identified and specific sets of mutations are found in different subtypes of nevi. Whereas a single mutation appears sufficient to initiate a nevus, but is not enough to result in melanoma, specific combinations of mutations have been identified in some melanocytic tumors that are regarded to be of low biologic potential. The term "melanocytoma" has recently been proposed by the World Health Organization to describe those tumors that demonstrate genetic progression beyond the single mutations that are found in nevi but are not frankly malignant. Melanocytomas occupy intermediate genetic stages between nevus and melanoma and likely have an increased risk of malignant transformation as compared to nevi. This review provides an update on the broad spectrum of melanocytic nevi and melanocytomas and outlines their key histopathologic and genetic features.

BRCA1-associated protein (BAP1)-inactivated melanocytic tumors

Although discussed using variable terminology, cutaneous BRCA1-associated protein (BAP1)-inactivated melanocytic tumor (BIMT) has been considered a discrete diagnostic entity since 2011. Here, we review the initial genomic studies that identified these distinct melanocytic tumors and the clinical and histopathological features that define these tumors. These epithelioid, predominantly dermal, and melanocytic tumors present as erythematous nodules and histopathologically have features that may overlap with Spitz nevi and nevoid melanoma. There is no sex predilection, and cutaneous BIMTs can appear at any age; however, in most familial (germline mutant) cases patients have multiple cutaneous tumors with a first diagnosis in the second or third decade of life; ocular melanoma and other tumors are increasingly identified in these kindreds with germline BAP1 mutation. These tumors have been described with a myriad of terms including: Wiesner nevus, nevoid melanoma-like melanocytic proliferation (NEMMP), BAP1 mutant Spitz nevus, BAP1 mutant nevoid melanoma, cutaneous BAPoma, and most recently cutaneous BIMT.

Common and not so Common Melanocytic Lesions in Children and Adolescents

The acquired melanocytic nevus is the most common lesion encountered by pediatric pathologists and dermatopathologists in their daily practice. In most cases, there are few difficulties in histopathologic diagnosis. However, it is the acquired melanocytic lesion known as the Spitz nevus, with its intrinsic atypical features which becomes the challenge since it exists along a histopathologic and biologic continuum from the atypical Spitz tumor to spitzoid melanoma. The frustration with some of these spitzoid lesions is that even the "experts" cannot agree as to the differentiation of one from the other even at the level of molecular genetics. Other melanocytic lesions are discussed including the congenital melanocytic nevus with its proliferative nodule(s) and melanoma as the ultimate complication. Although uncommon, cutaneous melanoma in the first 2 decades is emerging as a clinical problem especially in young women in the second decade of life. These are ultraviolet-associated neoplasms whose histopathologic and prognostic features are identical to the adult experience. Considerable progress has been made over the past 15 to 20 years in our understanding of cutaneous melanocytic lesions, but gaps still exist in the important group of spitzoid lesions. It can also be anticipated that more cutaneous melanomas in children will be seen in the future based upon epidemiologic studies.

Polypoid Spitz Nevus With a Halo Reaction

Approximately, 2% of Spitz nevi are polypoid; between 3.6% and 7.4% present with a halo reaction. In tandem, these low percentages make the presence of a polypoid Spitz nevus with a halo reaction uncommon; we have not found reports of any previous cases. In the current report, we present a polypoid Spitz nevus with a halo reaction on the back of a 10-year-old male and discuss the morphologic findings. The lesion showed preserved nuclear expression of BAP1. There was no immunohistochemical expression of BRAF and ALK, while the melanocytic cells expressed p16. Comparative genomic hybridization was performed, and no significant aberrations were found. Only 2 small losses were evidenced in chromosome 8. The patient has been followed now for 2 years with no recurrence.

Ambiguous melanocytic tumors with loss of 3p21

Germline loss-of-function mutations in BAP1 are associated with the development of cutaneous melanocytic tumors with some histopathologic characteristics seen in Spitz nevi. Similar melanocytic tumors occurring in a sporadic setting have been demonstrated to have biallelic loss of BAP1. In some of these sporadic tumors, loss of BAP1 occurs through mutation of 1 allele and genomic loss of the other. We screened our database of comparative genomic hybridization profiles of ambiguous melanocytic tumors to identify cases with a single genomic event involving loss of the BAP1 locus. The prevalence of tumors with a single genomic event involving loss of BAP1 was 6.7% in our study population. We further characterized the BAP1 status in 17 of these tumors with available additional material, confirming loss of BAP1 in all cases. We describe BAP1 loss in a blue nevus-like melanoma and further expand the histopathologic spectrum of spitzoid melanocytic neoplasms with BAP1 loss.

Combined BRAF(V600E)-positive melanocytic lesions with large epithelioid cells lacking BAP1 expression and conventional nevomelanocytes

Recently a group of spitzoid melanocytic proliferations with loss of BAP1 expression has been reported. The lesions may occur sporadically or as part of a familial cancer syndrome. They have distinct histopathologic features characterized by a nevus-like silhouette and cytologic composition of large epithelioid melanocytes with oval vesicular nuclei, distinct nucleoli, and abundant cytoplasm with well-defined cytoplasmic borders. A characteristic immunohistochemical finding is loss of nuclear labeling for BAP1. In contrast to classic Spitz nevi, the lesions carry the BRAF mutation. They may present as a pure large epithelioid cell proliferation or as a combined lesion in association with a conventional nevus. Here we report a series of 8 combined melanocytic lesions, in which a dominant large epithelioid cell proliferation with loss of BAP1 expression was associated and intimately admixed with a BAP1-positive conventional nevus. These biphenotypic lesions were from 6 patients, 3 female and 3 male, ranging in age from 16 to 59 years. Immunohistochemical analysis for BAP1 showed loss of nuclear labeling confined to the large epithelioid melanocyte subpopulation. The conventional melanocytes retained BAP1 expression. Both large epithelioid and conventional melanocytes were immunoreactive with the monoclonal antibody VE1, which recognizes the protein encoded by mutant BRAF. In 6 cases the conventional nevus component was a compound nevus of small "type B" melanocytes. In 2 cases, the nevus remnant was entirely intradermal. The lesions described herein may represent a peculiar combined melanocytic nevus variant. However, longer follow-up and more studies are needed to determine the biological potential of the BAP1-negative melanocyte proliferations.

Eponyms, morphology, and pathogenesis of some less mentioned types of melanocytic nevi

Some types of melanocytic nevi are seldom mentioned in the literature and are therefore less well known. In the current study, we focus on the concepts of eponyms, synonyms, clinical presentation, and morphology of the following types: Meyerson nevus, cockarde (or cockade) nevus, Hori nevus, Sun nevus, Hidanos nevus, Duperrat nevus, Spark nevus, nevus spilus, eclipse nevus, Kerl nevus, and Kopf nevus.

The natural history of halo nevi: a retrospective case series

BACKGROUND

The time period between onset of depigmentation around the halo nevus (HN) to complete resolution of the nevus and halo has not been well studied.

OBJECTIVE

We sought to better understand the natural history of the HN.

METHODS

A retrospective chart review of patients with a clinical diagnosis of HN selected from a private practice database (1994-2010) was performed. In all, 52 patients with 80 HN were identified. The current stage of the HN was determined by a follow-up questionnaire and physical examination of 36 patients with 56 HN.

RESULTS

Seven HN were excised. Of the remaining 49 HN, 51% (25) demonstrated no change in the halo or nevus after an average of 4.2 years; 14.3% (7) demonstrated partial nevus regression with persistence of the halo after an average of 6.7 years; 4.1% (2) demonstrated complete involution of the nevus with persistent halo depigmentation after an average of 7.7 years; 8.2% (4) demonstrated complete nevus involution with some repigmentation of the halo after an average of 11.8 years; 22.4% (11) demonstrated complete resolution of the nevus with complete repigmentation of the halo after an average of 7.8 years.

LIMITATION

Some subjects were lost to follow-up. The time of initial HN onset was dependent on patient recall.

CONCLUSION

These results demonstrate that HN typically persist for a decade or longer. A subgroup may progress through stages of involution with a return to normal-appearing skin, but even these lesions persisted for an average of 7.8 years. Education about the prolonged natural history of HN may reassure patients and avoid unnecessary excision.

State of the art, nomenclature, and points of consensus and controversy concerning benign melanocytic lesions: outcome of an international workshop

The following communication summarizes the proceedings of a one-day International Workshop focusing on the histology of benign melanocytic nevi. Areas of controversy identified in 6 focus sessions were the nomenclature and relationships among common nevi including nevi with halo reactions, traumatized nevi, "dysplastic" nevi, and nevi from particular anatomic sites; developmental biology and frequency of malignant transformation associated with congenital nevi; the characterization and biologic nature of atypical spitzoid neoplasms; the basic definition of particular melanocytic cellular phenotypes, and the nomenclature and biologic nature of many candidate blue nevi, combined nevi, and other controversial lesions such as deep penetrating nevus and pigmented epithelioid melanocytoma. Concentrated data collection and follow-up, molecular characterization, and future consensus Workshops may facilitate the resolution of some of these problems. The Group recommended the description of ambiguous or "borderline" lesions as tumors with indeterminate or uncertain biologic/malignant potential. The participants also advised that such lesions at a minimum should be managed by complete excision with clear surgical margins.

Spitz nevus: a clinicopathological study of 349 cases

Spitz nevus is an infrequent, usually acquired melanocytic nevus composed of epithelioid and/or spindle melanocytes that can occasionally be confused with melanoma. Currently, there are no immunohistochemical markers or molecular biology techniques that can be used to make an entirely safe diagnosis of Spitz nevus or melanoma in problematic cases. A retrospective study has been carried out that included all the cases diagnosed as Spitz nevus from our files. Follow-up information of the patients was unavailable. Three hundred forty-nine cases of unequivocal Spitz nevi were included, and their clinical and histopathological parameters were reviewed. One hundred and forty patients (40%) were 15 years old or younger, with a male to female ratio of 1:1. In patients older than 15 years, there was an evident predominance of women, with a male to female ratio of around 1:3. Spitz nevus was most commonly located on the lower extremities, followed by the trunk in both children and adults. Despite the fact that the head and neck were the third most common location in children, it was a much more frequent location in children than in adults. The constitution by epithelioid and/or spindled cells was the only histopathological finding present in 100% of cases. The other pathological findings studied were, from more to less frequent: maturation (72%), inflammatory infiltrate (70%), epidermal hyperplasia (66%), melanin (50%), telangiectasias (40%), Kamino bodies (34%), desmoplastic stroma (26%), mitosis (23%), pagetoid extension (13%), and hyalinization of the stroma (8%). Hyalinization was the only histopathological parameter that was statistically more frequent in adults than in children.

[Regression in malignant melanoma. Definition, etiopathogenesis, morphology and differential diagnosis]

Malignant melanoma is a neoplasm that more often tends to undergo regression. Clinically, variation in color is perhaps the most important hallmark of primary cutaneous melanoma. The change in color to white, off-white, blue-white and gray-white is a sign of (spontaneous) regression in malignant melanoma. Histopathologically the process starts with a dense lichenoid infiltrate of lymphocytes, and ends with fibrosis and/or melanosis within a thickened papillary dermis. The dense infiltrate of lymphocytes permeates the thin melanoma and destroys the atypical melanocytes in the epidermis and the papillary dermis. A key concern is how to define regression in a reproducible way. Using the following definition, a statistically significant risk of metastases can be demonstrated in thin melanomas (<1.0 mm) with extensive regression (>50%): "fibroplasia with an absence of epidermal and dermal involvement by melanoma cells, but allowing for (lentiginous) single-cell proliferation of atypical melanocytes along the dermo-epidermal junction".

Melanocytic nevi simulant of melanoma with medicolegal relevance

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

Low prevalence of RAS-RAF-activating mutations in Spitz melanocytic nevi compared with other melanocytic lesions

Melanocytic lesions, including Spitz nevi (SN), common benign nevi (CBN) and cutaneous metastatic melanoma (CMM), were analyzed for activating mutations in NRAS, HRAS and BRAF oncogenes, which induce cellular proliferation via the MAP kinase pathway. One of 22 (4.5%) SN tested showed an HRAS G61L mutation. Another lesion, a 'halo' SN, showed a BRAF V600E (T1796A) mutation. BRAF V600E mutations were found in two thirds (20/31) of CBN, while a further 19% (6/31) showed NRAS codon 61 mutations. One third of CMM (10/30) had various BRAF mutations of codon 600, and a further 6% (2/31) showed NRAS codon 61 mutations. Seventeen SN tested for loss of heterozygosity (LOH) at 9p and 10q regions, known to be frequently deleted in melanoma, showed LOH at the 9p loci D9S942 and IFNA. A further lesion was found with low-level microsatellite instability at one locus, D10S214. The low rate of RAS-RAF mutations (2/22, 9.1%) observed in SN suggests that these lesions harbor as yet undetected activating mutations in other components of the RAS-RAF-MEK-ERK-MAPK pathway. Germline DNA from members of 111 multiple-case melanoma families, representing a range of known (CDKN2A) and unknown predisposing gene defects, was analyzed for germline BRAF mutations, but none was found.

Fibrosis in regressing melanoma versus nonfibrosis in halo nevus upon melanocyte disappearance: could it be related to a different cytokine microenvironment?

BACKGROUND

It is not clear why melanocyte disappearance occurs without fibrotic evolution in halo nevus and with fibrotic evolution in regressing melanoma.

METHODS

Six halo nevi, seven regressing primary melanomas, and seven primary melanoma (PM) without regression were studied using immunohistochemistry for the phenotype of inflammatory infiltrate and the expression of cytokines involved in fibrogenesis or macrophage regulation. Melanocytes were also evaluated using electron microscopy.

RESULTS

CD8(+) lymphocytes predominated in halo nevus, whereas CD4(+) lymphocytes prevailed in melanoma; a few macrophages were only found in melanoma. Fibrogenic cytokines, IL-6, platelet-derived growth factor, and transforming growth factor-beta were only expressed in melanoma, whereas basic fibroblastic growth factor was also expressed in halo nevus. Antifibrotic cytokine tumor necrosis factor (TNF)-alpha was expressed at a higher degree in halo nevus. Cytokines involved in macrophage regulation were only expressed in melanoma.

CONCLUSIONS

Fibrogenic cytokines were more frequently expressed in melanoma than in halo nevus, irrespective of regression. At ultrastructural level, melanocytes showed a more activated status in regressing melanoma than in halo nevus, in compliance with a milieu richer in cytokines. Although the cytokine microenvironment does not completely justify the fibrotic evolution in regressing PM, the higher TNF-alpha expression in halo nevus suggests a possible role in nonfibrotic evolution of this lesion.

Spitz nevus is relatively frequent in adults: a clinico-pathologic study of 247 cases related to patient's age

Spitz nevus is a clinico-pathologic entity that can cause diagnostic concern, particularly in adults. Many studies have been performed to establish reliable histologic criteria, in the attempt to differentiate this lesion from melanoma. A series of 247 Spitz nevi, 6 of which were formerly classified as melanomas, were reviewed for clinical and histopathological parameters. Patients older than 20 comprised 66% of cases, with a predominance of women. The lower extremity was more affected in females of any age, whereas the trunk was more frequently involved in men over 40. Histopathologic examination showed the following differences among Spitz nevi related to age: acanthosis, parakeratosis, pagetoid infiltration, and Kamino bodies were more frequent in young people, whereas multinucleated melanocytes were more frequent in adults. The latter also had lesions that were less pigmented, with less maturation and more desmoplasia. At a mean follow-up of 94 months (range 52-172), recurrence at the site of biopsy or metastases were absent. In our study, a greater proportion of Spitz nevi occurred in adults than in previous series. Moreover, the relative incidence of Spitz nevus compared with melanoma in our population was higher than in other studies. Histopathologic criteria elaborated to diagnose Spitz nevus, applied to our cases, appeared reliable, allowing a correct diagnosis, even in adults.

Unusual clinical presentation of regression in a congenital melanocytic nevus

BACKGROUND

Regression of congenital melanocytic nevi is usually accompanied by the halo phenomenon and is considered a rare event.

OBJECTIVE

A 15-year-old woman presented for the evaluation of multiple halo nevi. She had on her trunk a figure-of-eight pigmentary lesion, which had been developed after the coalescence of two distinct congenital melanocytic nevi. Close to the indentation between the two portions of the lesion, there was an achromic rounded area, extending from the perinevic skin to the nevus, causing its partial regression.

METHODS AND MATERIALS

Dermoscopic examination disclosed a globular and homogeneous pattern, which was irregularly present at the edge of the achromic area. The histopathologic diagnosis was compound congenital melanocytic nevus with an eccentric area of regression.

CONCLUSIONS

In our case, the presence of a regression area in the surrounding skin and the association with multiple halo nevi suggest a similarity with halo phenomenon, despite the atypical "halo," which was discontinuous and eccentric.

Targetoid Hemosiderotic Nevus

BACKGROUND

Simulators of malignant melanoma comprise a heterogenous group of melanocytic and nonmelanocytic lesions of the skin. Among frequent clinical mimickers of melanoma are injured melanocytic nevi. Any change in the clinical appearance of a pre-existing nevus should alert the clinician to exclude the possibility of malignant transformation in order to early identify a lesion at a stage when complete cure can still be achieved.

OBJECTIVE

The purpose of this study was to present the clinical, dermoscopic and histopathologic findings of a series of acquired melanocytic nevi which abruptly developed a pigmented peripheral halo, presumably following minor trauma.

METHODS

A series of 6 cases of acquired melanocytic nevi which suddenly developed a targetoid halo were included in the study. All lesions were evaluated by dermoscopy. Three cases were surgically removed at different stages of evolution and submitted to histopathologic examination. In all cases, follow-up was obtained.

RESULTS

All the lesions arose on trauma-prone skin sites of young women. The sudden development of an asymptomatic, targetoid halo on a long-lasting, acquired exophytic nevus was the main presentation. Whereas the central nevus persisted, the ecchymotic halo ultimately disappeared. Histopathologic examination disclosed changes of the traumatized nevus in the central part, whereas the ring showed hemorrhage and hemosiderin deposits. Increased numbers of small vessels with hobnail characteristics were associated features.

CONCLUSIONS

Targetoid hemosiderotic nevus is a distinctive clinicopathologic variant of traumatized acquired melanocytic nevus which should be included in the list of clinical simulators of melanoma.

Consumption of the epidermis: a diagnostic criterion for the differential diagnosis of melanoma and Spitz nevus

The distinction between melanoma and its most important simulant, Spitz nevus, is usually made on microscopically. We point out "consumption of the epidermis" (COE) as an additional diagnostic criterion. We defined COE as thinning of the epidermis with attenuation of the basal and suprabasal layers and loss of rete ridges in areas of direct contact with neoplastic melanocytes. We analyzed 102 unequivocal melanomas and 125 unequivocal Spitz nevi for the presence of COE. COE had not been used in arriving at the diagnosis of these cases because we were unaware of the criterion at the time that the cases were first evaluated. COE was found in 88 of 102 (86%) of melanomas but only 12 of 125 (9.6%) of Spitz nevi (P < 0.001). We then looked for COE in an independent set of 61 ambiguous melanocytic lesions with overlapping histopathologic features that could not be classified unequivocally as Spitz nevus or melanoma. The cases were analyzed by comparative genomic hybridization (CGH) for aberration patterns suggesting a benign or a malignant process, based on previous studies. COE was found in only 6 of 42 (14%) of the ambiguous cases in which CGH suggested a benign process and 14 of 19 (74%) of the ambiguous cases in which CGH suggested melanoma (P < 0.001). Our data suggest that COE is a useful criterion in the evaluation of melanocytic neoplasms. Because COE was frequently found at the edges of ulcers in the majority of ulcerated melanomas, the thinning of the epidermis in COE may represent an early phase of ulceration. This may prove to be important in distinguishing ulceration due to an effect of the tumor from ulceration due to trauma, which would be expected not to have the same prognostic import. Future studies are required to analyze the prognostic value of COE itself.

Proliférations mélanocytaires de l’enfant

Melanocytic nevi in children can be acquired or congenital. The vast majority are benign but diagnosis can be difficult. Nevi in newborns and nodular proliferations in giant congenital nevi can display histological features that lend to their misdiagnosis as melanoma. Acquired melanocytic nevi in children are often Spitz nevi or related nevi. These lesions are too often misdiagnosed as melanoma. On the other hand, clinicians and pathologists must be aware that melanoma does occur in childhood, albeit very rarely. It is exceptionally rare in prepubescent individuals. It can be associated with the following risk factors: giant congenital nevus, family history of melanoma, xeroderma pigmentosum, and immunosuppression. Melanoma in children younger than 10 years of age is extremely rare and has different clinical and histopathological features than those that arise in postpubescents, often being confused with a Spitz's nevus. Consequently, the diagnosis is often made too late. It should be emphasized that thickness is the main prognostic parameter in childhood melanoma and that early diagnosis is also crucial in this age group. The lesion must therefore be examined in a complete excision and not in a partial biopsy, and if atypical features are present it must be reviewed by an expert. On the other hand extreme caution should be exercised when diagnosing melanoma in children, as some benign lesions exhibit similar histologic features.

Combined naevus: a benign lesion frequently misdiagnosed both clinically and pathologically as melanoma

BACKGROUND

Combined naevi are characterised pathologically by the presence of two or more different types of melanocytic naevi in a single lesion. They are prone to clinical and pathological misdiagnosis as melanoma. Misdiagnosis may result in inappropriate treatment, patient anxiety and medicolegal consequences.

AIMS

With the aim of reducing the incidence of misdiagnosis, this study documents the clinical and pathological features of a large series of combined naevi and describes how to distinguish them from melanoma.

PATIENTS AND METHODS

The slides of skin lesions from 220 patients that were coded as combined naevus between 1990 and 2001 were retrieved from the archival files of the Department of Anatomical Pathology, Royal Prince Alfred Hospital, Sydney, Australia. The clinical notes, letters from referring pathologists (for consultation cases) and slides were reviewed and for each lesion clinical and pathological features were assessed. Thirty-eight cases were excluded either because they included only one naevus component or because there were atypical pathological features in the slides available for review. The remaining 182 cases formed the study population.

RESULTS

The patients included 92 females and 87 males (1.1:1). In three cases the gender was not known. Mean and median patient ages were 29.6 and 28 years, respectively. The anatomical site of involvement was the trunk in 64 cases (35.2%), head and neck region in 43 cases (23.6%), upper extremity in 40 cases (22.0%), lower extremity in 18 cases (9.9%) and perineum and buttock region in eight cases (4.4%). In nine cases the site of involvement was not known. A pre-operative clinical diagnosis was recorded in 126 cases; of these, melanoma was suspected clinically in 33 cases (26.2%) while combined naevus was diagnosed clinically in only three cases (2.4%). Histologically, 180 cases included two different naevus components, and in two cases three different naevus components were present. The most common combination was a common acquired naevus of compound type associated with a blue naevus of deep penetrating naevus type; this occurred in 57 cases (31.3%). The referring pathologist recorded a preferred diagnosis in 88 of 122 consultation cases; of these, melanoma was suspected in 23 cases (26.1%) and in 23 cases combined naevus was favoured (26.1%).

CONCLUSIONS

Combined naevus is an uncommon type of melanocytic naevus that is frequently misdiagnosed both clinically and pathologically. Knowledge and recognition of the pathological features of combined naevi and the important features that distinguish them from melanomas should reduce the frequency of misdiagnosis.

The immunopathology of regression in benign lichenoid keratosis, keratoacanthoma and halo nevus

BACKGROUND

Regression is a phenomenon present in a variety of cutaneous lesions. It is likely that similar immunologic mechanisms explain the phenomenon of spontaneous regression occurring in the various lesions.

METHODS

Twenty-seven specimens, nine each of halo nevus, keratoacanthoma, and benign lichenoid keratosis, including three examples each of predominantly early, mid, and late regression were examined with antibodies to HLA-II, CD1a, CD3, CD4, CD8, CD20, CD34, CD56, and CD68.

RESULTS

Epidermotropism of inflammatory cells, including CD1a positive, CD68 positive, CD3 positive, and CD8 positive cells, was present in benign lichenoid keratosis and keratoacanthoma, but not in halo nevus. In halo nevus, the nests of halo nevus cells tended to be infiltrated by CD1a positive, CD68 positive, CD3 positive, and CD8 positive cells. The blood vessels exhibited endothelial cell swelling with luminal narrowing and disruption within the dermis of all lesions. The CD1a positive cells were increased in number in lesional epidermis except in keratoacanthoma lesions where the density of CD1a positive cells was increased in the epithelial lip, but decreased within the epithelial portion of the keratoacanthoma proper. Conversely, the CD8 positive cells were scarce in the dermis below the epithelial lip of the keratoacanthoma, but increased in the dermis of the neoplastic epithelium. CD1a positive cells were also seen throughout the dermal portion of the lesion, particularly at the lesion base. In halo nevus, the CD1a positive cells and CD68 positive cells within the lesions were larger than those in non-lesional skin, indicating activation. The composition of the inflammatory infiltrate varied within each lesion type according to stage of regression, but T-lymphocytes predominated.

CONCLUSION

Cytotoxic T-cells may be the final common denominator of regression in benign lichenoid keratosis, keratoacanthoma, and halo nevus. In halo nevus, cytotoxic T-cells may play the predominant role in regression. In keratoacanthoma and benign lichenoid keratosis, cytotoxic T-cells play a pivotal role, but additional mechanisms may also be involved in the phenomenon of regression. Benign lichenoid keratoses progress through stages of regression accompanied by varying proportions of inflammatory cells, including CD3, CD4, and CD8 positive T-lymphocytes, natural killer cells, macrophages and Langerhans cells.

Myxoid Spitz nevus

BACKGROUND

The deposition of extracellular mucin has not been described in Spitz nevus and herein such a case is reported.

METHODS

A 6-year-old male presented with a growing 1.0-cm pigmented lesion on his left anterior knee. The lesion was excised.

RESULTS

The histologic sections demonstrated a symmetrical and dome-shaped proliferation of spindle and epithelioid melanocytes with sharp lateral demarcation at the dermal-epidermal junction and within the superficial dermis. Features of Spitz nevus such as retraction from the epidermis, eosinophilic bodies, and uniform cytologic atypia were seen. Of interest, there was marked mucin deposition within the epidermal clefts and between the neoplastic cells. The mucin was highlighted by alcian blue and colloidal iron stains, and it was negative with mucicarmine and periodic acid-Schiff stains.

CONCLUSION

Awareness that soitz nevi can rarely have extracellular mucin helps in avoiding diagnostic pitfalls.

Congenital Spitz nevus clinically mimicking melanoma

The differentiation between atypical variants of Spitz nevus and melanoma is often difficult given the many clinical and histopathologic similarities between the two. We report a case of an infant with a congenital scalp lesion exhibiting clinical features of melanoma, including variegation and regression of pigmentation and a rapidly changing appearance. Histologic examination of the excised lesion revealed a benign congenital Spitz nevus. This case emphasizes the need for clinical and histologic correlation in determining the benign or malignant nature of atypical pigmented lesions in infants.

Spitz nevus and its histologic simulators

Spitz nevi continue to pose a considerable diagnostic challenge to the histopathologist. Key features of Spitz nevus and its variants are discussed and contrasted with the telltale signs of malignancy of "Spitzoid" melanomas. The importance of the histologic features of the deep, rather than superficial, part of the lesions is emphasized.

Plexiform spitz nevus

In 1999, Spatz et al. reported the first 2 cases of a plexiform variant Spitz nevus. We describe another case of this variant on the upper thigh of a 10-year-old boy and discuss the differential diagnosis. Histologically, it comprised nodules of epithelioid cells with a plexiform arrangement distributed throughout the superficial and deep dermis. The cells had moderate eosinophilic cytoplasm with vesicular nuclei and prominent nucleoli. Intranuclear inclusions were present focally. The tumor nodules were embedded in a myxoid stroma with intratumoral and peritumoral inflammatory cells including both lymphocytes and eosinophils. There were occasional melanin-containing spindle-shaped cells. An intraepidermal component could not be assessed, since the lesion was ulcerated. The differential diagnosis includes both melanocytic and nonmelanocytic lesions exhibiting a plexiform pattern of growth as well as myxoid lesions.

Conjunctival melanocytic nevi of childhood

Two young patients with conjunctival compound nevi are presented to illustrate two types of abnormalities that lead to difficulty in distinction of these nevi from invasive melanomas. In Case 1, inflammation is associated with disruption of the nevus cell architecture and cytologic atypia. In Case 2, the occurrence of a combined nevus (compound and blue nevus types) in the conjunctiva leads to diagnostic problems. Circumscription of the lesions, lack of mitoses in the substantia propria, and lack of pagetoid spread of atypical cells in the adjacent conjunctival epithelium support benign diagnoses in both cases.