BAP1‐deficient and VE1‐negative atypical Spitz tumor

Atypical Spitz tumor with loss of BAP1 or Wiesner nevus is a peculiar variant of intradermal spitzoid melanocytic neoplasm composed of epithelioid melanocytes with a sheet‐like growth pattern, abundant infiltrating lymphocytes and rare or absent mitotic activity. This subset of atypical spitzoid tumors is characterized by the BRAF^V600E mutation and loss of BAP1 expression. Recognition of these lesions is important because they can be a marker for a hereditary BAP1‐associated cancer syndrome. We present an unusual case of sporadic Wiesner nevus that had typical histopathologic features and a BAP1 but not a BRAF mutation. The biological significance of Wiesner nevus is controversial, and little is known about prognosis, particularly in atypical cases like this one.     

BRAF V600E mutation and the tumour suppressor IGFBP7 in atypical genital naevi

Background Atypical genital naevi (AGN) are naevi of special sites with atypical histological features that overlap with those of malignant melanoma. Activating BRAF mutations, identified in the majority of banal melanocytic naevi and cutaneous melanomas, are reportedly uncommon in naevomelanocytic proliferations in nonsun‐exposed sites. We have recently shown that constitutive activation of the BRAF‐MEK‐ERK signalling pathway in oncogenic BRAF‐positive naevi increases expression and secretion of IGFBP7, which induces senescence and apoptosis. Objectives To ascertain the frequency of BRAF V600E mutations in AGN compared with banal naevi without atypia. An additional aim was to assess the expression of IGFBP7 in oncogenic BRAF‐positive AGN. Methods Genomic DNA was isolated per protocol from seven genital naevi without atypia and 13 AGN for BRAF genotyping. Immunohistochemical staining for IGFBP7 was performed on all cases. Results The BRAF V600E mutation was identified in 43% of genital naevi without atypia and 23% of AGN (P = 0·61). In both groups, IGFBP7 expression was maintained in 67% of BRAF V600E‐positive cases. Conclusions The prevalence of BRAF V600E in AGN suggests that ultraviolet exposure is not essential for generating the mutation. The BRAF V600E mutational status appears to be of limited diagnostic utility in distinguishing genital naevi that exhibit atypia from those that do not. Similar to oncogenic BRAF‐positive common naevi without atypia, enhanced expression of the tumour suppressor IGFBP7 in oncogenic BRAF‐positive AGN supports that they are biologically inert.     

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.     

BRAF, NRAS and HRAS mutations in spitzoid tumours and their possible pathogenetic significance

Background The relationships between so‐called spitzoid tumours have proven difficult to understand. Objectives To address three questions: does spitzoid tumour morphological similarity reflect molecular similarity? Does Spitz naevus progress into spitzoid melanoma? Are ambiguous spitzoid tumours genuine entities? Methods BRAF, NRAS and HRAS mutations were analysed using single‐strand conformational polymorphism analysis and sequencing. Results Both Spitz naevi and spitzoid melanoma had a lower combined BRAF and NRAS mutation frequency compared with common acquired naevi (P = 0·0001) and common forms of melanoma (P = 0·0072), respectively. To look for evidence of progression from Spitz naevi to spitzoid melanoma, HRAS was analysed in 21 spitzoid melanomas, with no mutations identified. The binomial probability of this was 0·03 based on an assumption of a 15% mutation frequency in Spitz naevi with unbiased progression. Under these assumptions, HRAS mutations must be rare/absent in spitzoid melanoma. Thus, Spitz naevi seem unlikely to progress into spitzoid melanoma, implying that ambiguous spitzoid tumours cannot be intermediate degrees of progression. In addition, the data suggest that HRAS mutation is a potential marker of benign behaviour, in support of which none of three HRAS mutant spitzoid cases metastasized. Conclusions First, the morphological similarity of spitzoid tumours reflects an underlying molecular similarity, namely a relative lack of dependence on BRAF/NRAS mutations. Second, Spitz naevi do not appear to progress into spitzoid melanoma, and consequently ambiguous spitzoid tumours are likely to be unclassifiable Spitz naevi or spitzoid melanoma rather than genuine entities. Third, HRAS mutation may be a marker of Spitz naevus, raising the possibility that other molecular markers for discriminating Spitz naevi from spitzoid melanoma can be discovered.     

Spitzoid melanoma

Because spitzoid melanoma shares many histopathologic features with Spitz nevus, it is one of the most difficult lesions to diagnose in dermatopathology. Uncertainty exists in the medical literature about how to diagnose melanocytic proliferations including Spitz nevus and spitzoid melanoma. A misdiagnosis of a melanoma as Spitz nevus is one of the most frequent causes of malpractice lawsuits in surgical pathology and dermatopathology. This contribution provides a review of the clinical presentation, histopathology, ancillary studies, treatment, and the differential diagnosis of spitzoid melanoma.     

Mutated and amplified NRAS in a subset of cutaneous melanocytic lesions with dermal spitzoid morphology: report of two pediatric cases located on the ear

Extensive cytogenetic testing is slowly unveiling the complexity of the genomics of melanocytic tumors. NRAS mutations have been the first genetic abnormality described in malignant melanomas. We report the cases of two children, presenting a melanocytic lesion located on the ear. One appeared as a combined dermal clone inside a congenital nevus and the other as a centimetric purely dermal tumor. Both tumors were composed of spindled spitzoid melanocytes with atypical histologic features. aCGH and FISH revealed an amplification of the NRAS gene. Sequencing showed an exon 3 NRAS mutation. In the combined case, the amplification was limited to the spitzoid component, underscoring a possible phenotypic shift induced by the alteration. Similarly an overexpression of CyclinD1 and elevation of ki‐67 was found in the spitzoid component confirming a raise in proliferation. Such combination of mutation and copy number increase has been previously reported for the HRAS gene in a subset of Spitz nevi. Further studies must evaluate if mutated NRAS is also amplified in melanomas arising in this clinical setting. These combined alterations could represent an early event ultimately leading to malignancy.     

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.     

Genetic and epigenetic alterations in the differential diagnosis of malignant melanoma and spitzoid lesion

BACKGROUND: The histopathological differentiation of malignant melanoma and Spitz naevus often presents diagnostic problems. OBJECTIVES: We aimed to find out applicable diagnostic parameters other than routine pathology. METHODS: The cases included conventional melanomas and Spitz naevi as well as atypical spitzoid lesions that had posed diagnostic difficulties. We examined hotspots of mutation in the BRAF, NRAS and HRAS genes by polymerase chain reaction-based direct sequencing. We also analysed DNA copy number aberrations and the methylation of CpG sequences in several cancer-related genes by utilizing a novel methylation-specific multiplex ligation-dependent probe amplification method. RESULTS: Twenty three of 24 conventional melanomas showed at least one of the genetic and epigenetic alterations examined, although one acral melanoma did not show any alteration. By sharp contrast, 12 Spitz naevi with an unambiguous histopathology showed no or few chromosomal aberrations, no oncogene mutations and no methylation of CpG sequences. Of the 16 ambiguous spitzoid lesions, most of which were designated atypical Spitz tumour by one of the authors, all but one showed no mutations, no methylations and few copy number aberrations. However, three tumours showed copy number loss of the cyclin-dependent kinase inhibitor 2A gene (CDKN2A), an alteration observed frequently in melanomas but not found in conventional Spitz naevi. These results show that, although most atypical Spitz tumours do not differ from conventional Spitz naevi showing virtually no genetic and epigenetic aberrations, some cases may have chromosomal aberrations that include copy number loss of the CDKN2A gene. CONCLUSIONS: Genetic and epigenetic analyses may be useful as an additional diagnostic tool to distinguish between melanoma and Spitz naevus, and may help to define subgroups in atypical Spitz tumours.     

Classic and atypical Spitz nevi: review of the literature

Both classic and atypical Spitz nevi are uncommon melanocytic lesions usually presenting in children and adolescents. The classic Spitz nevus typically is benign and has characteristic clinical and histologic features. In contrast, the atypical Spitz nevus has an unknown clinical prognosis, and its clinical and histologic traits are loosely defined. Melanoma can have similar features to both classic and atypical Spitz nevi and must be ruled out in all cases. We review the literature on classic and atypical Spitz nevi, advances in differentiating both types of nevi from melanoma, and treatment options.     

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.     

Spitz样肿瘤研究进展

Spitz痣、非典型Spitz肿瘤和Spitz样黑素瘤的临床及组织学特征有重叠, 三者鉴别极具挑战。该文结合Spitz样肿瘤的临床和组织学特征, 综述其免疫组化特点和荧光原位杂交检测方法在本组疾病中的研究进展。     

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.     

Mutations of the BRAF gene in benign and malignant melanocytic lesions

A single-point mutation in exon 15 of the BRAF gene has recently been reported in a high percentage in cultured melanoma cells and in 6 of 9 primary melanomas examined. To evaluate the impact of the T1796A BRAF mutation, we screened primary melanomas, various types of nevi and lesions where a melanoma developed in an underlying nevus. We could detect the mutation in 28 of 97 (29%) melanomas and in 39 of 187 (21%) nevi, including blue nevi (0/20) and Spitz nevi (0/69), which did not carry the mutation. In melanomas with an underlying nevus, either the mutation was present in both the laser-microdissected nevus cells and the laser-microdissected melanoma cells (3/14) or both lesions were negative for the BRAF mutation except one case. In conclusion, mutations in exon 15 of the BRAF gene are nonspecific for progression of a nevus to a melanoma. Other so far unknown cofactors seem to be of importance.     

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.     

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。     

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.     

Oncogenic BRAF signalling increases Mcl‐1 expression in cutaneous metastatic melanoma

The Bcl‐2 family member Mcl‐1 is essential for melanoma survival; however, the influence of oncogenic BRAF signalling remains elusive. In this study, Mcl‐1 splice variant expression was determined in a panel of melanoma cell lines in relation to BRAF mutational status. Mcl‐1L mRNA expression was increased in melanoma cells compared with primary melanocytes with significantly increased mRNA and protein expression observed in BRAF^V600E mutant melanoma cells. Although no change in Mcl‐1S mRNA was observed, Mcl‐1S protein expression also increased in BRAF mutant melanoma cells. Additionally, while over‐expression of mutant BRAF^V600E increased both Mcl‐1L and Mcl‐1S expression, inhibition of hyperactive BRAF signalling resulted in decreased Mcl‐1L expression. These studies suggest that the regulation of Mcl‐1 expression by BRAF signalling is increased by oncogenic activation of BRAF, revealing a mechanism of apoptotic resistance which may be overcome by the use of more specifically targeted Mcl‐1 inhibitors.     

Aggressive melanoma in an infant with congenital melanocytic nevus syndrome and multiple,NRAS and BRAF mutation‐negative nodules

We report the case of a newborn boy with multinodular NRAS and BRAF mutation‐negative congenital melanocytic nevi and cerebral lesions compatible with congenital intraparenchymal melanosis. Histopathology from skin lesions showed atypical nodular melanocytic proliferation with marked melanocytic atypia and a large number of mitoses and apoptosis, indicating aggressive proliferation. The child developed several new subcutaneous tumors and multiple internal lesions, which were confirmed to be metastases, and died at 5 months of age. This case may represent an infantile melanoma developing from a giant congenital melanocytic nevus or a congenital melanoma.     

Update on dermoscopy of Spitz/Reed naevi and management guidelines by the International Dermoscopy Society

Spitzoid lesions represent a challenging and controversial group of tumours, in terms of clinical recognition, biological behaviour and management strategies. Although Spitz naevi are considered benign tumours, their clinical and dermoscopic morphological overlap with spitzoid melanoma renders the management of spitzoid lesions particularly difficult. The controversy deepens because of the existence of tumours that cannot be safely histopathologically diagnosed as naevi or melanomas (atypical Spitz tumours). The dual objective of the present study was to provide an updated classification on dermoscopy of Spitz naevi, and management recommendations of spitzoid‐looking lesions based on a consensus among experts in the field. After a detailed search of the literature for eligible studies, a data synthesis was performed from 15 studies on dermoscopy of Spitz naevi. Dermoscopically, Spitz naevi are typified by three main patterns: starburst pattern (51%), a pattern of regularly distributed dotted vessels (19%) and globular pattern with reticular depigmentation (17%). A consensus‐based algorithm for the management of spitzoid lesions is proposed. According to it, dermoscopically asymmetric lesions with spitzoid features (both flat/raised and nodular) should be excised to rule out melanoma. Dermoscopically symmetric spitzoid nodules should also be excised or closely monitored, irrespective of age, to rule out atypical Spitz tumours. Dermoscopically symmetric, flat spitzoid lesions should be managed according to the age of the patient. Finally, the histopathological diagnosis of atypical Spitz tumour should warrant wide excision but not a sentinel lymph‐node biopsy.     

Melanoma therapy: Check the checkpoints

Recent mutational and translational studies have revealed that the Ras/Raf/mitogen‐activated protein kinase kinase (MEK)/extracellular signal‐regulated kinase (ERK) pathway plays a key role in melanomagenesis. Mutations in NRAS and BRAF are found in the majority of melanomas resulting in the formation of constitutively active NRAS and BRAF molecules, which leads to the proliferation and survival of melanoma cells through the activation of MEK/ERK signals. Inhibitors of BRAF or MEK significantly extend the progression‐free survival and overall survival of melanoma patients compared with conventional chemotherapies. Combining BRAF and MEK inhibitors further enhances the clinical effectiveness. Cytotoxic T‐lymphocyte‐associated antigen 4 (CTLA‐4) is an immune checkpoint molecule that downregulates T‐cell activation by binding to B7 (CD80/CD86) molecules on antigen‐presenting cells. Programmed death receptor ligand 1 on melanoma cells negatively regulates T‐cell function by binding to the programmed death‐1 (PD‐1) receptor on T cells. Antibodies against CTLA‐4 and PD‐1 also enhance the survival of melanoma patients. In this review, we summarize the clinical effectiveness and adverse events of the BRAF inhibitors, MEK inhibitors and anti‐immune checkpoint antibodies in melanoma treatment.