Nevo de Spitz y otros tumores spitzoides en la infancia. Parte 1: aspectos clínicos,histológicos e inmunohistoquímicos

A Spitz nevus is a melanocytic neoplasm of epithelioid and/or spindle cells that usually appears in childhood. These lesions are by nature benign, but their features can sometimes make them difficult to distinguish from melanomas. Spitzoid melanocytic lesions have been grouped into 3 types in recent decades: Spitz nevi, atypical Spitz tumors, and spitzoid melanomas. Atypical Spitz tumors are spitzoid melanocytic proliferations that have atypical histopathologic features that are insufficient to support a diagnosis of melanoma. The malignant potential of these lesions is at present uncertain. This review examines the clinical, dermoscopic, and histopathologic features of this group of lesions.     

Spitz Nevi and Other Spitzoid Neoplasms in Children: Overview of Incidence Data and Diagnostic Criteria

Spitz nevi are benign melanocytic neoplasms characterized by epithelioid or spindle melanocytes or both. In some rare cases their presentation overlaps with the clinical and histopathologic features of malignant melanoma, so a differential diagnosis can be difficult to make. Intermediate forms between Spitz nevi and malignant melanoma, with unpredictable behavior, have been called atypical Spitz tumors. A literature search was performed to review the clinical, dermoscopic, genetic, and histopathologic aspects of spitzoid tumors. Spitz nevi mainly occur in children, with no predilection for sex, and in young women. Common sites are the head and lower arms, where Spitz nevi present as pink nodules or hyperpigmented plaques. Spitzoid lesions may have diverse dermoscopic patterns: vascular, starburst, globular, atypical, reticular, negative homogeneous, or targetoid. The management of spitzoid lesions can be invasive or conservative; surgical excision is usually reserved for those with doubtful features, whereas clinical and dermoscopic follow‐up is preferred for typical pediatric Spitz nevi. The role of sentinel lymph node biopsy in atypical Spitz tumors is debated. Immunohistochemistry and new molecular techniques such as comparative genomic hybridization, polymerase chain reaction, and fluorescence in situ hybridization offer new diagnostic perspectives, investigating genetic alterations that are specific for malignant melanoma or for Spitz nevi.     

Spitz nevus and atypical spitzoid neoplasm

Spitz nevus (SN) and Spitzoid malignant melanoma (SMM) represent benign and malignant counterparts at both ends of the spectrum of Spitzoid lesions. Atypical Spitzoid neoplasm (ASN) is a poorly defined and characterized category of melanocytic tumors with histologic features of both benign Spitz nevi and malignant melanomas. The group of ASN represents a mixture of Spitz nevi with atypical features and Spitzoid melanomas. However, at the current moment in time, histopathologists are not capable of differentiating between the 2 in some cases and are forced to place them in this ambiguous category, where the behavior of these lesions cannot be predicted with certainty. Because this group encompasses both benign and malignant lesions, and perhaps also a separate category of melanocytic tumors that behave better than conventional melanomas, some of these neoplasms can metastasize and kill patients, whereas others have no metastatic potential, and yet others might only metastasize to regional lymph nodes. Although diagnostic accuracy has improved over the years, many of these lesions remain controversial, and there is still poor interobserver agreement in classifying problematic Spitzoid lesions among experienced dermatopathologists. The objective of this review article is to summarize the most relevant information about SN and ASNs. At this time histologic examination remains the golden standard for diagnosing these melanocytic neoplasms. We therefore concentrate on the histopathologic, clinical, and dermoscopic aspects of these lesions. We also review the most recent advances in immunohistochemical and molecular diagnostics as well as discuss the controversies and dilemma regarding whether to consider sentinel lymph node biopsy for diagnostically ambiguous melanocytic neoplasms.     

Significant melanocytic lesions in infancy, childhood, and adolescence

Malignant melanoma is diagnosed yearly in approximately 300 persons under age 20 in the United States. Relatively recent advances in dermatology include the recognition of lesions felt to be potential precursors of malignant melanoma. Small congenital melanocytic nevi, present in 1 per cent of all newborn infants, may have a small but definite potential for developing malignant melanoma. Furthermore, despite inconclusive data, many leading dermatologists now advocate removal of these small congenital lesions. Giant congenital melanocytic nevi, with their strong predilection for undergoing malignant change, are removed surgically at an early age, often in multistaged procedures. Dermabrasion, once felt to have a role in the treatment of giant congenital nevi, does not remove the malignant potential of these lesions. The dysplastic nevus syndrome, recognized in 1976, identifies individuals at increased risk for developing melanoma. Adolescents who have the dysplastic nevus syndrome or who are members of families with the syndrome require close medical supervision and patient education. The benign Spitz nevus, with its histologic similarity to malignant melanoma, continues to challenge the dermatopathologist and clinician. These lesions--the Spitz nevus, dysplastic nevus, congenital melanocytic nevus, and malignant melanoma--must all be actively considered when regarding the many other benign melanocytic lesions found in infancy, childhood, and adolescence.     

Spitz样肿瘤320例临床及组织病理分析

【摘要】 目的 总结Spitz样肿瘤的临床及组织病理特征。方法 回顾2005年1月至2020年1月西京皮肤医院确诊的320例Spitz样肿瘤患者的临床及病理资料。结果 320例患者中,男141例,女179例,年龄0 ~ 65（12.5 ± 11.7）岁,病程1个月至30年;其中,Spitz痣307例,不典型Spitz肿瘤（AST）8例,Spitz痣样黑素瘤（SM）5例。皮损多为单发,可见于头面部、躯干和四肢,边界均清楚。307例Spitz痣皮损以黑色（132例,43.0%）和红色（108例,35.1%）为主,多数色素均匀（262例,85.3%）且表面平滑（272例,88.6%）。Spitz痣存在特殊临床亚型,11例 （3.6%）发生在斑痣上,11例 （3.6%）呈簇发性,6例（2.0%）播散性,7例（2.3%）结节性,1例（0.3%）为瘢痕疙瘩样。Spitz痣特征性病理表现包括表皮内痣细胞呈Paget样扩散（123例,40.1%）,真表皮交界处出现Kamino小体（74例,24.1%）,痣细胞呈水平带状（177例,57.8%）及楔形分布（118例,38.4%）,痣细胞巢周围出现裂隙（177例,57.8%）,可见生理性核分裂象（117例,38.1%）,核染色质均细腻。根据特殊组织病理表现,Spitz痣又分为色素性上皮样Spitz痣（9例,2.9%）、结缔组织增生性Spitz痣（13例,4.2%）、血管瘤样Spitz痣（8例,2.6%）、疣状Spitz痣（12例,3.9%）、黏液样Spitz痣（10例,3.3%）、晕痣样Spitz痣（4例,1.3%） 等。4例AST皮损为黑色,7例色素均匀,3例皮损表面粗糙;特征病理表现包括细胞均有轻度至中度的异型性,均可见核分裂象（7例为2 ~ 6个/mm2）,5例核染色质粗糙。3例SM皮损呈红色,4例色素不均匀,3例表面粗糙;特征病理表现包括黑素细胞呈Paget样扩散（3例）,瘤细胞呈无极性浸润性生长且均未见成熟现象,均有明显异型性,并可见病理性核分裂象（3例, > 6个/mm2）,核染色质均粗糙且核膜明显着色。结论 Spitz样肿瘤的临床及组织病理表现具有特征性,Spitz痣的临床及病理亚型繁多,AST同时具有Spitz痣和黑素瘤的临床及组织学特征。     

Spitz nevi display allelic deletions.

BACKGROUND: Spitz nevi are acquired benign melanocytic lesions that occur in childhood and adolescence. Histologically, they resemble malignant melanoma and were first termed benign juvenile melanoma. Several studies have attempted the difficult task of establishing diagnostic criteria to differentiate between Spitz nevi and malignant melanoma. OBJECTIVE: To elucidate sets of diagnostic criteria for differentiation between the 2 lesions. DESIGN: We aimed to search for allelic deletions in Spitz nevi and to evaluate whether loss of heterozygosity (LOH) or microsatellite instability (MSI) would be a valuable diagnostic tool to differentiate between Spitz nevi and malignant melanoma. SETTING: Two areas within each of 5 lesions were microdissected, and LOH and MSI were evaluated at chromosomes 6q (using polymorphic DNA marker D6S305), 9p21 (D9S171, IFNA, D9S265, and D9S270), 10q (D10S185), and 14q (D14S53). PATIENTS: Five Swiss patients with Spitz nevi. INTERVENTIONS: None. MAIN OUTCOME MEASURE: Allelic deletions may serve as a diagnostic tool to distinguish Spitz nevi from melanoma. RESULTS: All lesions were informative, displaying LOH or MSI with at least one marker. No LOHs were found at 14q. At 6q, MSI was found in 2 dissected areas from the same lesion; the remaining lesions were noninformative. Loss of heterozygosity was found in 2 of 6 areas at D9S171, 2 of 6 at IFNA, 3 of 6 at D9S270, 3 of 4 at D9S265, and 1 of 4 at D10S185. Microsatellite instability was found in 1 of 4 areas at D9S265. CONCLUSIONS: With the markers used in our study, Spitz nevi display LOH and MSI similar to those in melanoma. Analysis of LOH or MSI is therefore not a suitable diagnostic tool in distinguishing Spitz nevi from melanoma.     

Nucleolar organizer regions argyrophilic associated proteins in cutaneous melanocytic lesions.

We applied a simple silver staining technique to visualize nucleolar organizer regions associated proteins (AgNORs) for the study of 47 melanocytic lesions (20 malignant melanomas, 5 dysplastic nevi, 4 Spitz nevi, 2 Reed and Gartman's fusiform nevi and 16 melanocytic nevi). A statistically significant difference existed between the numbers of AgNORs per cell in benign and malignant lesions as a group. However, some overlapping counts were found, limiting the usefulness of the technique in differentiating benign from malignant lesions in individual cases.     

IMP‐3 expression in melanocytic lesions

Background: Insulin‐like growth factor‐II mRNA‐binding protein 3 (IMP‐3 ), a member of the insulin‐like growth factor mRNA‐binding protein family, is expressed in several human malignancies, including melanomas. However, the expression of IMP‐3 has not been explored in melanoma in situ, various histologic subtypes of invasive melanomas and atypical Spitz tumors. Methods: IMP‐3 immunostain was performed in 157 melanocytic lesions. Results: Nearly all benign (8/8), dysplastic (8/8) and Spitz nevi (8/9) were negative for IMP‐3. Focal IMP‐3 positivity was observed in 5/12 melanoma in situ and 4/15 superficial melanomas (Breslow depth ≤1 mm). Half (10/20) of deep melanomas (Breslow depth >1 mm) and 25/52 metastatic melanomas demonstrated strong IMP‐3 staining. IMP‐3 expression differs significantly between non‐desmoplastic melanomas (superficial and deep) and benign or dysplastic or Spitz nevi (p = 0.0427, respectively). Four of 23 desmoplastic melanomas expressed IMP‐3 , which was significantly different from deep melanomas (p = 0.0109). IMP‐3 stained 7 of 10 atypical Spitz tumors. The difference between atypical Spitz tumors and Spitz nevi was statistically significant (p = 0.0256). Conclusion: A malignant circumstance, such as non‐desmoplastic melanoma or atypical Spitz tumor, can be inferred when IMP‐3 is expressed, suggesting potential diagnostic value of IMP‐3 in melanocytic lesions. Yu L, Xu H, Wasco MJ, Bourne PA, Ma L. IMP‐3 expression in melanocytic lesions.     

The T1796A mutation of the BRAF gene is absent in Spitz nevi

BACKGROUND: BRAF, a serine/threonine kinase, is a component of the retrovirus-associated sequence (RAS)-RAF-extracellular-regulated protein kinase (ERK)-MAP kinase signal transduction pathway mediating signals from RAS to ERK. The T1796A single point mutation in exon 15 of the BRAF gene has recently been reported in a high percentage of malignant melanomas and benign melanocytic lesions such as congenital nevi, compound nevi, intradermal nevi and dysplastic nevi. The T1796A mutation has been shown to promote cell proliferation. METHODS: We screened 21 Spitz nevi and six spitzoid malignant melanomas for the presence of the T1796A BRAF mutation. RESULTS: The T1796A BRAF mutation could not be detected in any of the 21 Spitz nevi but was present in two of the six spitzoid malignant melanomas. CONCLUSIONS: Our results, in conjunction with data from a previous investigation, suggest that the melanocytic proliferation of Spitz nevi might be induced by components of the RAS-RAF-ERK-MAP kinase pathway different from BRAF, possibly combined with other genetic aberrations. The lack of the T1796A BRAF mutation might be of practical importance in distinguishing Spitz nevi from other melanocytic lesions simulating Spitz nevi as a part of a future complex diagnostic assay.     

Understanding spitzoid tumours: new insights from molecular pathology

Spitzoid tumours are a morphologically diverse group of lesions that share histological similarity to the Spitz naevus, a benign melanocytic skin tumour. Distinguishing classic Spitz naevi from cutaneous malignant melanoma is usually achievable on standard histology sections, but occasionally equivocal lesions are encountered that show features intermediate between these two entities and consequently generate considerable clinical and histopathological concern. The nomenclature and diagnostic criteria for spitzoid lesions are not standardized and this article begins by considering the adverse effect this has on our understanding of spitzoid tumour biology. Investigations of some of the hallmark features of cancer and neoplasia in spitzoid tumours are described, and the contribution of these studies to our understanding of spitzoid tumour biology is considered, along with their potential diagnostic utility. These studies compare spitzoid tumours with better-characterized melanocytic lesions, and from such comparisons assumptions concerning the biological nature of different spitzoid tumours can be made. In contrast, investigations of the mitogen-activated protein kinase (MAPK) pathway and DNA gains and losses have suggested that Spitz naevi may be genetically distinct from other melanocytic tumours. The studies that led to this conclusion are reviewed, as well as subsequent work examining whether the same applies to all spitzoid tumours. Possible explanations for the considerable inconsistencies within some of these data are explored. Finally, potential pathways of tumour progression within spitzoid lesions are considered, with an emphasis placed upon insights gained from investigations of MAPK genes and DNA gains and losses.     

Spitz nevi and other Spitzoid lesions part II. Natural history and management

For dermatologists, evidence-based management guidelines for Spitz tumors have not been established. Despite the lack of a standardized approach, most dermatologists recommend the excision of Spitz tumors occurring in adults and adopt more conservative measures towards pediatric cases. The histopathologic attributes and the clinical scenario are factored into management in each case. While the metastatic behavior of certain Spitz tumors is well known, the malignant potential of these lesions remains unclear because they only rarely result in negative outcomes. The risks and benefits of adjunctive measures, such as sentinel lymph node biopsy and interferon use, remain untested and are subjects of ongoing controversy. (In part II of this continuing medical education article, we will continue to use the terminology defined in part I for purposes of continuity. "Spitz tumor" is used as the umbrella term for the entire category of lesions, "common Spitz nevi" refers to only the most typical lesions seen in pediatric cases, and "atypical Spitz tumors" encompass the "all other" category, which continues to cause debate.).     

Argyrophilic staining of nucleolar organizer region count and morphometry in benign and malignant melanocytic lesions

Differentiation between malignant melanomas (MMs) and benign nevi based on histologic features can sometimes be difficult. This study evaluated the diagnostic effectiveness of argyrophilic staining of nucleolar organizer regions (AgNORs) in separating benign nevi from MMs by assessing 27 compound nevi (CN), 20 dysplastic nevi (DN), 10 Spitz nevi (SN), and 24 MMs. Both AgNOR count and morphology variables were measured from the superficial, middle, and deep zones of the lesions using video image analysis. Malignant melanomas had a significantly greater AgNOR number per nucleus, mean AgNOR area per nucleus, and variation in AgNOR area per nucleus compared with all types of benign nevi (p < 0.05). In multivariate discriminant analysis using a combination of four AgNOR counts and morphometric parameters, all CN and DN, 8 of 10 SN, and 23 of 24 MMs could be correctly classified as benign or malignant. The results suggest that both AgNOR count and morphology help to separate benign and malignant melanocytic lesions and that the combination of both sets of parameters improves their discriminating ability.     

Nevo de Spitz y otros tumores spitzoides en la infancia. Parte 2: características citogenéticas y moleculares. Pronóstico y tratamiento

Melanocytic neoplasms with spitzoid morphology (Spitz nevi, atypical Spitz tumors, and spitzoid melanomas) may be benign or malignant. Because the malignant potential of atypical Spitz tumors is uncertain, the proper therapeutic approach has been much debated over the years. Promising new techniques for molecular analysis have enabled better predictions of the biological behavior of these tumors. We review their cytogenetic features and prognosis and also provide an update of the most recent recommendations for management.     

Comparison of pHH3, Ki-67, and survivin immunoreactivity in benign and malignant melanocytic lesions

Differentiating malignant melanoma from benign melanocytic lesions can be challenging. We undertook this study to evaluate the use of the immunohistochemical mitosis marker phospho-Histone H3 (pHH3) and the proliferation markers Ki-67 and survivin in separating malignant melanoma from benign nevi. Sixty-six melanocytic lesions (18 malignant melanomas, 8 Spitz nevi, 20 dysplastic nevi, and 20 compound nevi) were stained with antibodies to pHH3, Ki-67, and survivin. No pHH3 expression was detected in the dermis of compound and dysplastic nevi. Rare mitoses were observed in the superficial dermis in 3 of 8 Spitz nevi (37%). Staining for pHH3 was higher in malignant melanomas [average 25 per 10 high-power field (HPF), range 2-75 per 10 HPF] than in Spitz nevi (average 0.5 per 10 HPF, range 0-2 per 10 HPF) and was heterogeneously distributed in the malignant melanomas compared with a superficial dermal location in Spitz nevi. There was no cytoplasmic staining for survivin in any of the 66 melanocytic lesions and no nuclear staining in any of the benign ones. Survivin nuclear staining was present in 12 of 18 cases of malignant melanoma (67%) with an average index of 7% (range 0%-15%). In benign melanocytic lesions, the Ki-67 index was less than 5% (range 0%-4%) and staining was present close to the dermo-epidermal junction compared with an average index of 27% in melanomas (range 5%-50%) and a generally heterogeneous pattern of staining throughout the dermis. pHH3 and Ki-67 can be useful adjuncts to histopathology to separate malignant melanoma from benign nevi. pHH3 is especially useful to highlight mitoses and to rapidly assess the mitotic activity in melanocytic lesions.     

HMB-45 staining in benign and malignant melanocytic lesions. A reflection of cellular activation.

The antibody HMB-45 used as an immunohistochemical reagent has often been labeled as a marker for melanoma, even though some benign lesions have been noted to show positive staining reactions with this reagent. Biopsy specimens from 225 benign and malignant melanocytic lesions were examined after immunoperoxidase staining for S-100 protein and HMB-45. The lesions studied included common acquired nevi, spindle cell and epithelioid cell nevi (Spitz nevi), cellular blue nevi, deep penetrating nevi, congenital nevi, nevi from hormonally reactive areas (genital), malignant melanoma, and desmoplastic malignant melanoma. A positive reaction for HMB-45 was seen in the dermal component in a high percentage of each of these types of lesions except for the common acquired nevi and the desmoplastic malignant melanomas that were uniformly negative for HMB-45 in the dermal component. HMB-45 correlates with melanosome production and thus a melanocytic origin of HMB-45-positive cells. HMB-45 may correlate best with factors that stimulate melanocytic proliferation and production of melanosomes.     

Expression of p-27 (kip1) in nevi and melanomas

Histopathologic criteria are usually sufficient for the accurate distinction of benign from malignant melanocytic lesions of the skin. A minority of cases, however, particularly Spitz nevi, continue to pose a vexing diagnostic challenge. Recent research, however, suggests that p27 (kip1), a cell cycle inhibitory protein, may prove helpful in predicting the biologic behavior of a diverse array of human neoplasms. We analyzed 63 melanocytic lesions of the skin (21 Spitz compound nevi, 21 compound nevi, 21 melanomas, and a variety of other benign and malignant cutaneous neoplasms as a control group) for expression of p27 (kip1). The distribution of immunoreactivity was analyzed by quantifying nuclear staining in each case without knowledge of the diagnosis or outcome. Clinical history and follow-up information were obtained by chart review. There was no difference in the expression of p27 between Spitz nevi (labeling index=38.4+/-4.0), compound nevi (labeling index=40.1+/-4.8), and melanoma (labeling index=42.3+/-5.1). Logistic regression failed to show any difference in p27 labeling index between the nevi and melanoma (p=0.736). These results indicate that antibodies to p27 are not useful in distinguishing between these melanocytic lesions.     

Differential diagnosis of Spitzoid melanocytic neoplasms

Atypical Spitzoid neoplasms represent a controversial and incompletely defined diagnostic category for lesions with intermediate architecture and cytomorphology between Spitz nevus and melanoma. The vast majority of these neoplasms have a good overall prognosis. Only a small proportion of patients will end up developing distant metastases and death. The distinction between Spitz tumours with atypical features and Spitzoid melanoma remains difficult on clinical and histological grounds and the prediction of the biological behaviour of those tumours even with sentinel lymph node biopsy is impossible. Tools such as immunohistochemistry, genetic analysis, mutation analysis and mass spectometry have contributed to the better understanding of those tumours and may be useful in the differential diagnosis of Spitzoid tumours.     

Agminated Spitz Nevi: Case Report and Review of the Literature

Spitz nevi are benign melanocytic lesions with many histologic similarities to malignant melanoma. A case of agminated Spitz nevi on a 2‐year‐old boy's left cheek is reported and 41 other cases of agminated Spitz nevi are reviewed. In this case, two biopsies were performed on two different‐appearing lesions and the results of both biopsies showed Spitz nevi.     

Multiple agminated Spitz nevi arising on a café au lait macule: review of the literature with contribution of another case

The majority of Spitz nevi are acquired solitary lesions. Multiple Spitz nevi are rare and may develop on hyperpigmented skin. We report a 16-year-old girl with multiple Spitz nevi arranged on a café au lait macule. Immunohistochemistry showed positivity for S-100 and HMB-45. Of interest, expression of Polo-like kinase (PLK), a novel proliferation marker that recently proved to be positive in up to 98% of malignant melanoma cells, showed positivity in 40% of the nevus cells. The clinical development of multiple Spitz nevi is not yet clear, as they are preferentially excised. Reviewing 70 cases in the literature we found that multiple agminated Spitz nevi occur more frequently than reported previously. In about one-third of these cases Spitz nevi arose on congenitally hyperpigmented skin.     

Immunohistochemical expression of cyclooxygenage-2 in melanocytic skin lesions

Background Several reports have shown expression of cyclooxygenase‐2 (COX‐2) in malignant skin tumors. COX‐2 has also recently been reported as a marker of malignant melanoma (MM). Objective Our aim was to investigate whether there is a difference in the immunohistochemical expression of COX‐2 between malignant and benign melanocytic lesions of the skin. Methods We selected 40 archival cases of MM including 10 cases of superficial spreading melanoma, 10 of lentigo maligna melanoma, 10 of nodular melanoma, and 10 of acral lentiginous melanoma. For comparison, we also selected 35 benign melanocytic lesions, which included 15 nonatypical nevi and 10 atypical nevi. The remaining 10 cases were Spitz nevi. COX‐2 immunohistochemical staining was performed, and intensities were assessed quantitatively. Results The MM group and the benign melanocytic nevi group showed a highly statistically significant difference in the intensity of COX‐2 expression (P < 0.0001). Staining intensity in the dermal component of MM cases also showed a tendency to increase with increasing tumor depth. By contrast, the intensity of the dermal component in the melanocytic nevi group decreased with increasing depth as the nevus cells matured from type A to type C cells. No statistical difference was noted between the MM and Spitz nevi cases (P = 0.20). Conclusions Malignant melanoma shows stronger immunohistochemical expression of COX‐2 than benign melanocytic nevi. Although COX‐2 cannot be used alone to differentiate MM from melanocytic nevi, it may serve as an aid in the differential diagnosis of melanocytic skin lesions.