Spitz naevus: diagnostic problems and their management implications

Spitz naevus is an uncommon, benign melanocytic neoplasm that shares many clinical and histological features with melanoma. While Spitz naevi typically occur in children and melanomas typically occur in adults, either tumour can occur in a patient of any age. In cases displaying all or most of the classical histological features, particularly when occurring in a young patient, it is possible to make a confident diagnosis of Spitz naevus. However, for those lesions with atypical features it may be difficult to predict the biological behaviour with certainty from the histopathological appearance. Hence, such tumours have been referred to by a variety of names including atypical Spitz naevus, atypical Spitz tumour and spitzoid tumours of uncertain malignant potential. However, even acknowledged experts in dermatopathology have a low concordance in distinguishing Spitz naevus with atypical features from melanoma. In this article, we highlight the histopathological features of Spitz naevi and those that may be useful in distinguishing Spitz naevi from melanomas. A suggested practical guide to clinical management of such lesions is provided.     

Allelic imbalance in the diagnosis of benign,atypical and malignant Spitz tumours

To test the diagnostic usefulness of allelic imbalance (AI) analysis based on routinely paraffin-embedded tissue, a series of 55 benign Spitz naevi, Spitz tumours with uncertain malignant potential, and malignant Spitzoid melanomas was investigated. Laser microdissection was used to ensure representative sampling of lesional cells and to investigate AI in separate tumour areas of four melanomas. AI was found in 2/12 (17%) typical Spitz naevi, 3/9 (33%) atypical Spitz tumours, 12/17 (65%) atypical Spitz tumours suspicious for melanoma and 15/17 (88%) Spitzoid melanomas. Additional immunohistochemical staining for Ki-67 using the MIB-1 antibody revealed positive deeply situated lesional cells in 0/6 (0%) Spitz naevi, 1/8 (13%) atypical Spitz tumours, 5/14 (35%) atypical Spitz tumours suspicious for melanoma, and 7/14 (50%) Spitzoid melanomas, respectively. Two of the melanomas examined for AI in separate tumour areas showed intratumoural genetic heterogeneity. In view of the finding of AI and deeply situated Ki-67 positive cells not only in melanomas but also in Spitz tumours with uncertain malignant potential, these approaches appear to have no direct diagnostic applicability for the distinction between benign and malignant Spitz tumours. Further molecular studies will be required to determine whether Spitz tumours and Spitzoid melanomas are unrelated entities, or whether there is a true spectrum of tumour progression.     

Nuclear pseudoinclusions in melanocytic naevi and melanomas.

Melanocytes in melanocytic naevi and melanomas can display great variation. The presence of nuclear pseudoinclusions (NPI) is said to be useful in the histological and cytological differential diagnosis of malignant melanoma. The prevalence and characteristics of NPI in a series of 493 naevi and 50 melanomas are described. NPI were found in 31% of adult naevi, 30% of congenital naevi from children, 42% of Spitz naevi, 20% of dysplastic naevi, and 56% of melanomas. The presence of NPI is not a reliable criterion for differentiating melanoma from benign melanocytic lesions, although it is useful in distinguishing melanocytic from non-melanocytic tumours.     

Fluorescence in situ hybridization for the differential diagnosis between Spitz naevus and spitzoid melanoma

Requena C, Rubio L, Traves V, Sanmartín O, Nagore E, Llombart B, Serra C, Fernández‐Serra A, Botella R & Guillén C
(2012) Histopathology  61, 899–909 Fluorescence in situ hybridization for the differential diagnosis between Spitz naevus and spitzoid melanoma Aims: The differential diagnosis between Spitz naevus and spitzoid melanoma can be extremely difficult, or even impossible. In recent years, many attempts have been made to find specific histopathological or immunohistochemical markers, although none has proved successful. Because the prognosis and treatment of each are very different, it is important to distinguish between these entities. We evaluated the ability of the fluorescence in situ hybridization (FISH) assay–designed to detect the copy number of the RREB1 (6p25), MYB (6q23) and CCND1 (11q13) genes and of centromere 6 (Cep 6)–in order to distinguish between Spitz naevus and spitzoid melanoma. Methods and results: We evaluated 12 spitzoid melanomas and six Spitz naevi from our records. The diagnosis of both conditions was based on previously described histopathological criteria. We obtained valuable results for FISH in eight spitzoid melanomas and five Spitz naevi. Chromosomal aberrations were detected in seven of the eight spitzoid melanomas (FISH‐positive) and in none of the five Spitz naevi. The FISH‐negative spitzoid melanoma was the least typical in its group. Conclusions: FISH was able to distinguish between Spitz naevus and spitzoid melanoma, with a sensitivity of 87.5% and a specificity of 100%. Our findings suggest that FISH could prove a useful tool in the differential diagnosis between these entities.     

Classifying melanocytic tumors based on DNA copy number changes

Melanoma and benign melanocytic nevi can overlap significantly in their histopathological presentation and misdiagnoses are common. To determine whether genetic criteria can be of diagnostic help we determined DNA copy number changes in 186 melanocytic tumors (132 melanomas and 54 benign nevi) using comparative genomic hybridization. We found highly significant differences between melanomas and nevi. Whereas 127 (96.2%) of the melanomas had some form of chromosomal aberration, only 7 (13.0%) of the benign nevi cases had aberrations. All seven cases with aberrations were Spitz nevi, in six of which the aberration was an isolated gain involving the entire short arm of chromosome 11. This aberration was not observed in any of the 132 melanomas. We also analyzed the 132 melanomas for genetic differences depending on anatomical site, Clark's histogenetic type, and sun-exposure pattern. We show that melanomas on acral sites have significantly more aberrations involving chromosomes 5p, 11q, 12q, and 15, as well as focused gene amplifications. Melanomas classified as lentigo maligna melanomas or as occurring on severely sun-damaged skin showed markedly more frequent losses of chromosomes 17p and 13q. This study shows a pattern of chromosomal aberration in melanoma that is distinct from melanocytic nevi and should be further evaluated as a diagnostic test for melanocytic lesions that are now ambiguous. In addition, we show marked differences in the genetic make-up of melanomas that depend on anatomical location and sun-exposure pattern indicating that potential therapeutic targets might vary among melanoma types.     

Presence of cytogenetic abnormalities in Spitz naevi: a diagnostic challenge for fluorescence in-situ hybridization analysis

Martin V, Banfi S, Bordoni A, Leoni‐Parvex S & Mazzucchelli L
(2012) Histopathology  60, 336–346
Presence of cytogenetic abnormalities in Spitz naevi: a diagnostic challenge for fluorescence in‐situ hybridization analysis Aims: Spitz naevi are difficult to diagnose, because of significant overlap with melanomas. It has been recently demonstrated that the LSI RREB1(6p25)/LSI MYB(6q23)/LSI CCND1(11q13)/CEP6 fluorescence in‐situ hybridization (FISH) assay is a reliable tool with which to distinguish benign naevi and melanomas. Little is known about its diagnostic usefulness in Spitz naevi. Methods and results: We investigated 51 patients with Spitz naevi and long‐term median follow‐up (8.18 years) with the multicolour FISH probe. Control groups included 11 benign naevi and 14 melanomas. Spitz naevi from 32 (63%) patients did not show cytogenetic abnormalities (FISH?). In contrast, Spitz naevi from 19 (37%) patients showed changes in the investigated loci (FISH+). Spitz naevi with the FISH+ profile showed chromosome X polysomy in 14/18 (78%) patients. All Spitz naevi with the FISH? profile were disomic. All melanomas displayed a FISH+ profile, and 4/11 (36%) showed chromosome X polysomy. No differences in clinicopathological features were detected between Spitz naevi with and without genetic abnormalities. Conclusions: The presence of gene copy number changes in Spitz naevi as detected by FISH is higher than expected, and Spitz naevi at the genetic level represent a heterogeneous group. The findings of similar cytogenetic alterations in Spitz naevi and melanomas suggest that there should be cautious interpretation of FISH analysis in this setting.     

Common and uncommon variants of melanocytic naevi

Numerous variants of melanocytic naevi have been described. Their main pathological significance lies in their distinction from melanoma, as well as being precursors and risk markers for melanoma. Various degrees of atypia such as cytological atypia, architectural disorder and pagetoid spread (pagetoid melanocytosis) may be present in naevi and need to be recognised as appropriate for the subtype. As well as the distinction from melanoma, naevi must be differentiated from atypical lesions, such as atypical Spitz tumours, which do not fulfil all the criteria of melanoma, may be benign or malignant and have been called 'melanocytic tumours of unknown malignant potential'. The diagnostic grey area also includes a group of benign atypical naevi which are difficult to subclassify into specific entities. In this paper naevi are divided into: firstly, the common acquired group with a brief discussion of junctional, compound and intradermal naevi, minor variants such as halo and balloon naevi and the major variants that may cause problems -- dysplastic naevi, naevi of special sites, recurrent naevi and Spitz naevi; secondly, congenital naevi; thirdly, blue naevi and related lesions (dermal melanocytoses); and finally, combined naevi. The emphasis is on diagnostic pathological features and the differential diagnosis with melanoma.     

Molecular cytogenetics of cutaneous melanocytic lesions – diagnostic,prognostic and therapeutic aspects

Blokx W A M, van Dijk M C R F & Ruiter D J
(2010) Histopathology 56 , 121–132
Molecular cytogenetics of cutaneous melanocytic lesions – diagnostic, prognostic and therapeutic aspects This review intends to update current knowledge regarding molecular cytogenetics in melanocytic tumours with a focus on cutaneous melanocytic lesions. Advantages and limitations of diverse, already established methods, such as (fluorescence) in situ hybridization and mutation analysis, to detect these cytogenetic alterations in melanocytic tumours are described. In addition, the potential value of more novel techniques such as multiplex ligation‐dependent probe amplification is pointed out. This review demonstrates that at present cytogenetics has mainly increased our understanding of the pathogenesis of melanocytic tumours, with an important role for activation of the mitogen‐activated protein kinase (MAPK) signalling pathway in the initiation of melanocytic tumours. Mutations in BRAF (in common naevocellular naevi), NRAS (congenital naevi), HRAS (Spitz naevi) and GNAQ (blue naevi) can all cause MAPK activation. All these mutations seem early events in the development of melanocytic tumours, but by themselves are insufficient to cause progression towards melanoma. Additional molecular alterations are implicated in progression towards melanoma, with different genetic alterations in melanomas at different sites and with varying levels of sun exposure. This genetic heterogeneity in distinct types of naevi and melanomas can be used for the development of molecular tests for diagnostic purposes. However, at the moment only few molecular tests have become of diagnostic value and are performed in daily routine practice. This is caused by lack of large prospective studies on the diagnostic value of molecular tests including follow‐up, and by the low prevalence of certain molecular alterations. For the future we foresee an increasing role for cytogenetics in the treatment of melanoma patients with the increasing availability of targeted therapy. Potential targets for metastatic melanoma include genes involved in the MAPK pathway, such as BRAF and RAS. More recently, KIT has emerged as a potential target in melanoma patients. These targeted treatments all need careful evaluation, but might be a promising adjunct for treatment of metastatic melanoma patients, in which other therapies have not brought important survival advantages yet.     

An update on cutaneous melanocytic lesions

Significant advances in our understanding of melanocytic neoplasms at the genomic level have occurred in the last decade. This includes identifying initiating genomic events which correlate highly to morphology for benign intermediate and malignant melanocytic neoplasms. Among spitzoid melanocytic neoplasms, mRNA sequencing has revealed specific genomic fusions correlating to morphologic features. Additionally a number of biomarkers for intermediate and malignant grade lesions have been identified. This includes molecular studies looking for copy number aberrations or specific mutations in spitzoid neoplasms, deep penetrating nevi, and blue nevi. mRNA expression profiling has become an important test for prognostication of melanoma. In this review, we provide an overview of the molecular landscape and summarize the histomorphology of a subset of melanocytic neoplasms, including blue nevi, deep penetrating nevi, pigmented epithelioid melanocytomas, Spitz nevi, and BAPomas. We further discuss novel biomarkers for prognostication and the recent updates to melanoma staging.     

Spitz naevi and malignant melanomas of childhood and adolescence

We reviewed 33 cases of Spitz naevus and 19 of malignant melanoma in patients aged 20 years or less who were evaluated at our institution from 1950 to 1975 and followed-up for up to 32 years. The histological findings were studied prior to review of clinical data. There were no malignant melanomas in patients less than 9 years old; almost half (15/33) of the Spitz naevi were in this age group. Among the 25 histological criteria evaluated in the 52 lesions, the most striking differences between malignant melanomas and Spitz naevi were a higher degree of pagetoid spread, cellular pleomorphism, nuclear hyperchromasia and mitotic activity in the malignant melanomas, and a more prominent spindle cell component in Spitz naevi. We stress the importance of cytological as well as architectural criteria in distinguishing between Spitz naevi and malignant melanomas and emphasize the pitfalls that may be encountered because of overlap in histological features between the two groups.     

DEK expression in melanocytic lesions

The diagnosis of malignant melanoma presents a clinical challenge and relies principally on histopathological evaluation. Previous studies have indicated that increased expression of the DEK oncogene, a chromatin-bound factor, could contribute to the development of melanoma and may be a frequent event in melanoma progression. Here, we investigated DEK expression by immunohistochemistry in a total of 147 melanocytic lesions, including ordinary nevi, dysplastic nevi, Spitz nevi, melanoma in situ, primary invasive melanomas, and metastatic melanomas. Most benign nevi (ordinary, dysplastic, and Spitz nevi) were negative or exhibited weak staining for DEK, with only 4 of 49 cases showing strong staining. Similar to benign nevi, melanoma in situ also demonstrated low levels of DEK expression. In contrast, the expression of DEK in primary invasive melanomas was significantly higher than benign nevi (P < .0001). Moreover, DEK expression was significantly increased in deep melanomas (Breslow depth >1 mm) and metastatic melanomas as compared with superficial melanomas (Breslow depth ≤1 mm) (P < .05). Our findings indicate that DEK overexpression may be a frequent event in invasive melanomas, and further augmentation of DEK expression may be associated with the acquisition of ominous features such as deep dermal invasion and metastasis. These data suggest a role of DEK in melanoma progression.     

IMP-3 is a novel progression marker in malignant melanoma

Insulin-like growth factor-II messenger RNA (mRNA)-binding protein-3 (IMP-3), also known as K homology domain-containing protein overexpressed in cancer (KOC) and L523S, is a member of the insulin-like growth factor-II mRNA-binding protein family and is expressed during embryogenesis and in some malignancies. IMP-3 expression in melanocytic neoplasms has not been investigated. Fifty-six melanocytic neoplasms from 48 subjects were immunohistochemically studied using a monoclonal antibody against L523S/IMP-3. IMP-3 expression in melanoma was significantly higher than in Spitz nevi (P<0.05), and the staining intensity in the Spitz nevi was weak. IMP-3 expression in metastatic melanoma was significantly higher than in primary cutaneous melanoma with a Breslow depth 相似文献   

S100 protein, neurone specific enolase, and nuclear DNA content in Spitz naevus

The differentiation between Spitz naevus and melanoma is at times difficult. The present study was undertaken to define means to positively identify such melanocytic tumours of doubtful malignancy. Immunohistochemical staining intensity for S100 protein and neurone specific enolase (NSE) was measured in sections of 35 Spitz naevi using a microcomputer image analysis system. The data were compared with results previously obtained from 19 cases of malignant melanoma and 16 benign compound naevi. Disaggregated cells from paraffin-embedded material were stained by the Feulgen technique for DNA estimation. The nuclear DNA content distributions were measured using the same image analysis system. Compared with the malignant cases, the Spitz naevi showed significantly lower staining intensity for both S100 protein (P less than 0.0001) and NSE (P less than 0.0001). When compared with the benign compound naevi, the staining intensity was significantly lower for S100 protein (P = 0.003). The nuclear DNA distribution in Spitz naevi proved to be a normal diploid pattern in 31 cases. Four cases showed a small proportion of hyperdiploid nuclei. The results show that Spitz naevi can be significantly distinguished from malignant melanoma by staining intensity for S100 protein and NSE. A normal diploid DNA content distribution appears to be typical for Spitz naevi. Spitz and benign compound naevi show dissimilar expression of S100 protein which may indicate different patterns of differentiation in these two types of lesion. The image analysis equipment used in this study is accurate, simple to use, produces results rapidly, and is economic. Therefore, it is clinically practicable.     

VS38 immunostaining in melanocytic lesions.

AIMS: To investigate the immunoreactivity of a range of melanocytic lesions, both benign and malignant, with the monoclonal antibody VS38. This was recently described as a marker of reactive/neoplastic plasma cells and, therefore, is useful in the diagnosis of plasmacytoma/myeloma and lymphomas with plasmacytic differentiation. This study was prompted by the recent observation that a plasmacytoid melanoma arising in the nasal cavity was strongly immunoreactive with VS38, which was therefore a potential source of major diagnostic error. METHODS: The Streptavidin-peroxidase complex technique was used on paraffin wax embedded sections of 167 melanocytic lesions. Diaminobenzidine (DAB) was used as chromogen for non-pigmented or lightly pigmented lesions and nickel/DAB for more heavily pigmented lesions. RESULTS: Positive immunostaining for VS38 was seen in 14.5% (10/69) of benign naevi (including 40% (four of 10) of Spitz naevi), 10.5% (two of 19) of dysplastic naevi/in situ melanomas, 92% (35/38) of primary cutaneous melanomas, 100% (four of four) of primary mucosal melanomas, 91.7% (33/36) of recurrent/metastatic melanomas, and 100% (one of one) of clear cell sarcomas of soft tissues. CONCLUSIONS: VS38 immunostaining is frequently positive in primary and recurrent/metastatic malignant melanoma and is also reactive less commonly with benign naevi. These results should be borne in mind when this recently described marker of normal/neoplastic plasma cells is used to identify tumour lineage, particularly in tumours arising at unusual sites, such as in the nasal cavity. The possibility of malignant melanoma should be actively considered and excluded in any undifferentiated tumour which shows VS38 immunoreactivity.     

Wnt ligand expression in malignant melanoma: pilot study indicating correlation with histopathological features.

AIMS: Secreted Wnt ligands are key proteins regulating cell-cell interactions and cell growth and differentiation. These proteins, along with other components of the Wnt signalling pathway, are involved in the malignant transformation of various human cancers, including malignant melanoma. This study defines the expression of several members of the Wnt ligand family and correlates their expression with histological characteristics. METHODS: The expression of Wnt2, Wnt5a, Wnt5b, Wnt7b, and Wnt10b was defined by in situ, antisense RNA hybridisation of paraffin wax embedded sections of benign naevi and malignant melanoma. Immunoperoxidase based antibody staining was used to define the expression of frizzled (Fz) receptors. RESULTS: All naevi tested strongly expressed Wnt2, Wnt5a, Wnt7b, and Wnt10b. Melanomas characterised by small, uniform cells expressed each of the Wnts in a pattern similar to that seen for benign naevi. In contrast, melanomas characterised by large, pleomorphic cells expressed Wnt10b but did not express Wnt2 and had low levels of expression of Wnt5a. Expression of Wnt7b was variable in these melanomas. Fz receptor expression was present at a low level in normal epithelium and all naevi and melanomas. CONCLUSIONS: The expression pattern of Wnt ligands in malignant melanoma correlates with histopathological features and may provide a basis for the molecular classification of this disease.     

KP1 (CD 68) staining of malignant melanomas

The monoclonal antibody KP1, which recognizes the CD 68 antigen on macrophages and myeloid precursors, was tested on 28 malignant (primary and metastatic) melanomas, 28 naevi, and 17 skin biopsies showing either normal (10) or hyperplastic melanocytes (7). Sixteen of 20 primary melanomas and six of eight metastatic melanomas showed variable numbers of KP1 positive tumour cells. All but five benign melanocytic proliferations (two Spitz naevi and three intradermal naevi), as well as normal and hyperplastic melanocytes were negative. These results indicate that difficulties may occur with the use of KP1 in the differential diagnosis between melanomas and neoplasms derived from histiocytes-macrophages, and that the expression of CD 68 antigen might be related to tumour progression in melanocytic cells.     

Reduced expression of p16 and p27 is correlated with tumour progression in cutaneous melanoma

AIMS: To determine if the cyclin dependent kinase inhibitors (CDKIs) p16 and p27 show reduced expression in the progression from benign to malignant melanocytic tumours, and to correlate these findings with patient prognosis. METHODS: Ninety-two melanocytic tumours were assessed for immunohistochemical expression of p16 and p27. These specimens included nine compound naevi, 10 dysplastic naevi, 17 thin (<1 mm) melanomas, 22 thick (>1 mm) melanomas, nine in-transit metastases, 13 lymph node metastases, and 12 soft tissue metastases. Clinicopathological information on the 39 patients with melanoma primaries was obtained from the Sydney Melanoma Unit database. The median follow up period was 43.3 months. RESULTS: A significant loss of expression of p16 and p27 was found with tumour progression. Positive expression of p27 was found in all compound and dysplastic naevi but only 43.6% of melanoma primaries. Expression of p27 was greater in lymph node and in-transit metastases (63.6%), but lower in soft tissue metastases (36.4%). Positive expression of nuclear p16 was evident in 73.7% of benign naevi, 28.2% of primary melanomas and 14.7% of metastatic melanomas. Neither p16 nor p27 expression was significantly correlated with overall survival, disease free survival or other clinicopathological markers. CONCLUSIONS: The CDKIs p16 and p27 are associated with tumour progression in melanoma, but do not reliably predict recurrence or survival.     

Two cases of unusual acral melanocytic tumors: illustration of molecular cytogenetics as a diagnostic tool

The differential diagnosis between benign Spitz nevus and malignant melanoma may present considerable difficulties in some cases. Here we report 2 unusual melanocytic tumors with spitzoid features developing in acral sites of Japanese patients to illustrate the use of comparative genomic hybridization (CGH) to classify these lesions. Case 1 was a 12-mm-thick, >2 cm-diameter nodule on the sole of a 37-year-old man. Case 2 was a subungual tumor of the left index finger in a 13-year-old boy. CGH showed absence of chromosomal aberrations in case 1 and multiple aberrations in case 2, including focused amplification as previously described in acral melanomas. Case 1 was free of disease after 2.5 years of follow-up, whereas case 2 developed lymph node metastasis. We conclude that molecular techniques such as CGH can be of diagnostic help in the classification of histologically ambiguous lesions.     

Expression of neurotrophins and their receptors in pigment cell lesions of the skin

The neurotrophins (NTs) are a group of growth factors involved in the development of the nervous system and presumed to play a role in neural crest-derived tumours. The expression of three NTs (NGF, BDNF, and NT-3) and their receptors (NTRs; i.e. low-affinity pan-NT receptor p75, Trk-B, and Trk-C) was studied in frozen sections of benign and malignant cutaneous pigment cell lesions, using immunohistochemistry. In order to understand the possible role of these growth factors and their receptors in the progression of primary cutaneous malignant melanomas (PCMMs), their distribution in the radial (RGP) and vertical (VGP) growth phases was particularly studied. While most of the common acquired naevi were unreactive, Spitz and blue naevi showed scattered immunoreactive cells, especially for the p75 NTR. Dysplastic naevi, but not common naevi, expressed NT-3 in their junctional component. PCMM and melanoma metastases often showed a diffuse pattern of immunostaining. NT-3 was significantly more frequently expressed in the RGP of PCMMs than in the junctional component of benign naevi, whereas more extensive immunoreactivity for NGF was found in the VGP of PCMMs, compared with the RGP; metastases more frequently expressed NGF, BDNF, and Trk-B than PCMMs. Interestingly, neurotropic melanoma expressed all NTs/NTRs except Trk-B. These immuunohistochemical data confirm suggestions from previous in vitro studies that autocrine loops of certain NTs and their respective receptors may be involved in melanoma progression; in addition, NT-3 may be involved in the junctional growth of dysplastic naevi. The precise role of these growth factors in melanoma, however, will await further functional studies.