Distinct Patterns of Acral Melanoma Based on Site and Relative Sun Exposure

Treatment of acral and mucosal melanoma: Current and emerging targeted therapies

Targeted therapies revolutionized the management of patients with advanced and metastatic cutaneous melanoma. However, despite recent advances in the understanding of the molecular drivers of melanoma and its treatment with targeted therapies, patients with rare and aggressive melanoma subtypes, including acral melanoma (AM) and mucosal melanomas (MM), show limited long-term clinical benefit from current targeted therapies. While patients with AM or MM and BRAF or KIT mutations may benefit from targeted therapies, the frequency of these mutations is relatively low, and there are no genotype-specific treatments for most patients with AM or MM who lack common driver mutations. The poor prognosis of AM and MM can also be attributed to the lack of understanding of their unique molecular landscapes and clinical characteristics, due to being under-represented in preclinical and clinical studies. We review current knowledge of the molecular landscapes of AM and MM, focusing on actionable therapeutic targets and pathways for molecular targeted therapies, to guide the development of more effective targeted therapies for these cancers. Current and emerging strategies for the treatment of these melanoma subtypes using targeted therapies are also summarized.

Update on nail unit histopathology

Histopathologic evaluation of the nail unit is an essential component in the diagnosis of nail unit disorders. This review highlights recent updates in nail unit histopathology and discusses literature covering a wide range of nail disorders including melanoma/melanocytic lesions, squamous cell carcinoma, onychomatricoma, onychopapilloma, onychomycosis, lichen planus, and other inflammatory conditions. Herein we also discuss recent literature on nail clipping histopathology, a useful and noninvasive diagnostic tool that continues to grow in popularity and importance to both dermatologists and dermatopathologists.

Differences in the Clinical and Molecular Profiles of Subungual Melanoma and Acral Melanoma in Asian Patients

Subungual melanoma (SUM) is a rare type of malignant melanoma that arises beneath the nails. SUM is categorized as a type of acral melanoma (AM), which occurs on the hands and feet. SUM is an aggressive type of cutaneous melanoma that is most common among Asian patients. Recent studies reveal that SUM and AM might have different molecular characteristics. Treatment of melanoma relies on analysis of both clinical and molecular data. Therefore, the clinical and molecular characteristics of SUM need to be established, especially during metastasis. To define the mutation profiles of SUM and compare them with those of AM, we performed next-generation sequencing of primary and metastatic tumors of SUM and AM patients. Subungual location was a better independent prognostic factor than acral location for better overall survival (p = 0.001). Patients with SUM most commonly had the triple wild-type (75%) driven by GNAQ (58%) and KIT (25%) mutations, whereas patients with AM had BRAF (28.6%) and RAF (14.3%) molecular types of mutations. Single-nucleotide variations (SNVs) were more common in SUM than in AM, whereas copy number alterations (CNAs) were more common metastatic lesions of AM. Metastatic tumors in patients with SUM and AM showed increases in CNAs (43% and 80%, respectively), but not in SNVs. The number of CNAs increased during metastasis. When compared with AM, SUM has distinct clinical and molecular characteristics.

Melanoma in skin of color: Part I. Epidemiology and clinical presentation

Although there is a higher incidence of melanoma among non-Hispanic White individuals, melanoma is diagnosed at more advanced stages and associated with worse survival rates among individuals with skin of color (SOC). The proportions of melanoma subtypes differ across racial groups, with acral lentiginous melanoma and mucosal melanoma representing higher proportions of melanoma diagnoses in individuals with SOC compared to White individuals. The recognition of distinct differences in anatomic locations and dermatoscopic patterns may facilitate the appropriate differentiation of physiologic from pathologic pigmentation. The first article of this continuing medical education series will focus on the epidemiology and clinical presentation of melanoma in individuals with SOC, with the aim of improving early diagnoses and clinical outcomes.

Distinct genomic features in a retrospective cohort of mucosal, acral, and vulvovaginal melanomas

BACKGROUND

Compared with sun-exposed melanomas, less is known regarding the pathogenesis of sun-protected melanomas. Sun-protected melanomas share many epidemiologic factors, but their genetic heterogeneity is not well studied.

OBJECTIVE

We investigated the genomic profile of acral, mucosal, and vulvovaginal melanomas. We hypothesize that mucosal melanomas, recognized for their uniquely aggressive clinical behavior, have distinct genomic features.

METHODS

We performed whole transcriptome messenger RNA and DNA (1711 genes) sequencing, messenger RNA expression profiling, tumor mutational burden, ultraviolet signature, and copy number variants analysis on 29 volar/digital acral, 7 mucosal, and 6 vulvovaginal melanomas.

RESULTS

There was significant genetic heterogeneity, particularly in acral melanomas, with 36% having BRAF alterations, whereas other melanomas had none (P = .0159). Nonzero ultraviolet signatures were more frequent in acral melanomas, suggesting greater ultraviolet involvement. Mucosal melanomas formed a distinct group with increased expression of cell cycle and proliferation genes. Various targetable aberrations were identified, such as AURKA and ERBB2, in mucosal and acral melanomas, respectively.

LIMITATIONS

The sample size was a small.

CONCLUSION

There is significant genetic heterogeneity among sun-protected melanomas. Mucosal melanomas have upregulation in cell cycle and proliferation genes, which may explain their aggressive behavior. Ultraviolet radiation plays some role in a subset of acral but not other melanomas.

Nail Apparatus Melanoma: Current Management and Future Perspectives

Nail apparatus melanoma (NAM) is a rare type of cutaneous melanoma that belongs to the acral melanoma subtype. NAM is managed principally in accordance with the general treatment for cutaneous melanoma, but there is scarce evidence in support of this in the literature. Acral melanoma is genetically different from non-acral cutaneous melanoma, while recently accumulated data suggest that NAM also has a different genetic background from acral melanoma. In this review, we focus on recent advances in the management of NAM. Localized NAM should be surgically removed; amputation of the digit and digit-preserving surgery have been reported. Sentinel lymph node biopsy can be considered for invasive NAM for the purpose of accurate staging. However, it is yet to be clarified whether patients with metastatic sentinel lymph nodes can be safely spared completion lymph node dissection. Similar to cutaneous melanoma, immune checkpoint inhibitors and BRAF/MEK inhibitors are used as the first-line treatment for metastatic NAM, but data on the efficacy of these therapies remain scarce. The therapeutic effects of immune checkpoint inhibitors could be lower for NAM than for cutaneous melanoma. This review highlights the urgent need to accumulate data to better define the optimal management of this rare melanoma.

Solar Ultraviolet Radiation, Skin Cancer and Photoprotective Strategies in South Africa†

The most recent data relating to the incidence of, and mortality from, the three commonest forms of skin cancer, namely basal cell carcinoma (BCC), squamous cell carcinoma (SCC) and cutaneous melanoma (CM), in the Black African, Colored, Asian/Indian and White population groups in South Africa are reviewed. While exposure to solar ultraviolet radiation is the major environmental risk factor for BCC in all four groups, for SSC in the White and Asian/Indian groups and for CM in the White group, this is unlikely to be the case for most SCCs in the Black African group and for most CMs in the Black African and Asian/Indian groups. Strategies for practical personal photoprotection in South Africa are discussed with particular emphasis on people at heightened risk of skin cancer including the White population group, those with HIV or oculocutaneous albinism and outdoor workers.

Acral Melanocytic Neoplasms: A Comprehensive Review of Acral Nevus and Acral Melanoma in Asian Perspective

Acral melanocytic neoplasms, including acral melanocytic nevus and acral melanoma, are common melanocytic lesions in Asian populations. Both lesions occur on the volar surface of the hands and feet, and on nail units. Acral melanocytic nevi occur on the arch area of the sole, whereas acral melanomas frequently occur on weight-bearing areas of the sole, and on the fingernails. Therefore, the development of acral melanoma may be associated with chronic pressure, physical stress, or trauma. Dermoscopy is a useful adjunctive diagnostic tool for differential diagnosis. Acral melanocytic nevus is characterized by a parallel furrow pattern, whereas acral melanoma has a parallel ridge pattern. Genetic alterations are also different between the two types of lesion. BRAF and NRAS mutations are common in acral melanocytic nevus, whereas acral melanoma shows lower rates of KIT, NF1, BRAF, and NRAS mutations and remarkable copy number variations in genes such as CCND1, CDK4, hTERT, PAK1, and GAB2. Sentinel lymph node biopsy is important for staging and prognosis. Contemporary treatments for melanoma include targeted therapy for mutations and immunotherapy, such as anti-PD1 inhibitors.

Clinical features, molecular pathology, and immune microenvironmental characteristics of acral melanoma

Acral melanoma (AM) has unique biology as an aggressive subtype of melanoma. It is a common subtype of melanoma in races with darker skin tones usually diagnosed at a later stage, thereby presenting a worse prognosis compared to cutaneous melanoma. The pathogenesis of acral melanoma differs from cutaneous melanoma, and trauma promotes its development. Compared to cutaneous melanomas, acral melanomas have a significantly lighter mutational burden with more copy number variants. Most acral melanomas are classified as triple wild-type. In contrast to cutaneous melanomas, acral melanomas have a suppressive immune microenvironment. Herein, we reviewed the clinical features, genetic variants, and immune microenvironmental characteristics of limbic melanomas to summarise their unique features.

Does acral melanoma need a distinctive prognostic staging system?

Linked Article: Wei et al. Br J Dermatol 2022; 186 :977–987 .

Actionable Mutation Profile of Sun-Protected Melanomas in South America

ABSTRACT

Melanomas that arise in sun-protected sites, including acral and oral mucosal melanomas, are likely under the control of unique, specific mechanisms that lead to mutagenesis through various pathways. In this study, we examined somatic mutations in tumors by targeted sequencing using a custom Ion Ampliseq Panel, comprising hotspots of 14 genes that are frequently mutated in solid tumors. Tumor DNA was extracted from 9 formalin fixation, paraffin-embedded sun-protected melanomas (4 primary oral mucosal melanomas and 5 acral lentiginous melanomas), and we identified mutations in the NRAS, PIK3CA, EGFR, HRAS, ERBB2, and ROS1 genes. This study reveals new actionable mutations that are potential targets in the treatment of photo-protected melanomas. Additional studies on more of these melanoma subtypes could confirm our findings and identify new mutations.

Limb melanomas: acral melanomas have worse survival

BACKGROUND

The anatomic site of primary melanoma is significantly correlated with survival, and extremity melanomas have better prognosis than trunk or head and neck melanomas.

AIM

The aim of this study was to review and evaluate the prognostic factors and survival outcomes associated with both upper and lower extremity melanomas.

METHODS

A total of 524 limb-located melanomas were analyzed retrospectively.

RESULTS

Lower extremity melanomas were predominant in number and feet/toes melanomas were more frequently found in the elderly. Acral lentiginous melanomas were found to affect more frequently lower limbs and showed mainly distal distributions for both limbs. However, acral melanomas were more often ulcerated and they were more frequently BRAF wild-type melanomas associated with significant lymphovascular invasion. Foot and toe melanomas relapsed more frequently than leg melanomas. The 5-year overall survival rates for upper and lower limbs were the same, 62%. The finger (p = .0001) and toe (p = .005) melanomas had worse overall survivals than arm and leg melanomas, respectively. Both overall and disease-free survivals of acral melanoma patients were found worse than those of nonacral melanoma patients, p = .0001 and p = .001 respectively. Despite not having adjusted by Breslow, ulceration and nodal involvement status, acral location per se could be associated with poorer outcome in our retrospective study.

CONCLUSION

Even though they were not found to be correlated with major predictors of poor prognosis, acral melanomas significantly predict poor survival.

Subungual melanoma with blue naevus-like morphological features: a clinicopathological retrospective analysis of nine cases

Melanocytic lesions in the nail apparatus are often challenging. Both subungual melanomas (SUM) and blue naevus of the nail are very rare. Occasionally, melanomas may mimic blue naevus histologically. Benign and malignant blue melanocytic lesions are commonly associated with G protein mutations, a distinct abnormality not associated with conventional subungual melanomas. We describe the clinical, histological and immunohistochemical features of nine cases of SUM with blue naevus-like morphological features. Mutations in exon 4 and 5 of GNAQ and GNA11 were investigated in two cases, which showed no mutations. RNA-seq of one case revealed unknown mutations along with mutations in ATM, METK and ARID1A. Our study delineates a variant of SUM that mimics blue naevus. Awareness of this pitfall is important when evaluating heavily pigmented lesions around the nail in order to avoid misdiagnosis. Appropriate sampling of subungual lesions and clinicopathological correlation are paramount to reach the correct diagnosis.

Acral Lentiginous Melanoma: A United States Multi-Center Substage Survival Analysis

Background

Acral lentiginous melanoma is associated with worse survival than other subtypes of melanoma. Understanding prognostic factors for survival and recurrence can help better inform follow-up care.

Objectives

To analyze the clinicopathologic features, melanoma-specific survival, and recurrence-free survival by substage in a large, multi-institutional cohort of primary acral lentiginous melanoma patients.

Methods

Retrospective review of the United States Melanoma Consortium database, a multi-center prospectively collected database of acral lentiginous melanoma patients treated between January 2000 and December 2017.

Results

Of the 433 primary acral lentiginous melanoma patients identified (median [range] age: 66 [8–97] years; 53% female, 83% white), 66% presented with stage 0–2 disease and the median time of follow-up for the 392 patients included in the survival analysis was 32.5 months (range: 0–259). The 5-year melanoma-specific survivals by stage were 0 = 100%, I = 93.8%, II = 76.2%, III = 63.4%, IIIA = 80.8%, and IV = 0%. Thicker Breslow depth ((HR) = 1.13; 95% CI = 1.05–1.21; P < .001)) and positive nodal status ((HR) = 1.79; 95% CI = 1.00–3.22; P = .050)) were independent prognostic factors for melanoma-specific survival. Breslow depth ((HR = 1.13; 95% CI = 1.07–1.20; P < .001), and positive nodal status (HR = 2.12; 95% CI = 1.38–3.80; P = .001) were also prognostic factors for recurrence-free survival.

Conclusion

In this cohort of patients, acral lentiginous melanoma was associated with poor outcomes even in early stage disease, consistent with prior reports. Stage IIB and IIC disease were associated with particularly low melanoma-specific and recurrence-free survival. This suggests that studies investigating adjuvant therapies in stage II patients may be especially valuable in acral lentiginous melanoma patients.

More than just acral melanoma: the controversies of defining the disease

Acral melanoma (AM) is a malignant cutaneous melanocytic tumour specifically located on the palms, soles, and nail apparatus, which are areas of glabrous (hairless) skin. Acral lentiginous melanoma, a subtype of AM, represents a histopathological subtype diagnosis of cutaneous melanoma with unique morphological and structural features. Despite clear definitions, the misuse of these terms and the inconsistency in reporting the histopathological features of AM cases have become a major obstacle to the study of the disease. In this review, we discuss the epidemiology, histopathological features, prognosis, and genetic profile of AM, highlighting the differences observed when histopathological subtypes are considered. The increasing global effort to characterise AM cases from ethnically diverse populations would benefit greatly from a more consistent classification of the disease.

Establishment of cultured primary acral melanoma cells and animal models for Chinese patients

Acral melanoma is the major subtype of melanoma in Chinese patients. However, a majority of current studies focused on non-acral melanoma. Most immortalized melanoma cell lines and primary cells were not from acral melanoma. Besides, there are rarely reports about methods for establishing primary acral melanoma cell cultures and related animal models. Here, we present four new human primary acral melanoma cell lines. To determine the mutational profile of the established primary melanoma cells for future targeted use, we performed exome sequencing. We next examined cell proliferation of the primary acral melanoma cells by colony-formation assays and CCK8 assay. We also evaluated the proliferative and metastatic potential of XYAM-4 in vivo. We report a detailed protocol for establishing cultured primary acral melanoma cells for Chinese patients and related animal models. We also summarize the features in our acral melanoma cell lines and the existing acral melanoma cell lines. This will provide an effective research tool for research on drug responses and individualized treatment for Chinese patients and comparative studies of melanomas between western and Chinese populations.

Comprehensive clinicopathological and molecular analysis of primary malignant melanoma of the oesophagus

AIMS

This study was performed to elucidate the clinicopathological characteristics, genetic alterations and therapeutic targets of primary malignant melanoma of the oesophagus (PMME).

METHODS AND RESULTS

The clinicopathology and molecular pathology of 13 PMME cases and 10 skin malignant melanoma (SKMM) cases were analysed with next-generation sequencing (NGS) and immunohistochemistry. The 3-year overall survival rate and the median survival time for PMME patients were 23.1% and 11.9 months, respectively. Three (23.1%) and eight (61.5%) PMME cases showed a papillary structure and lymph node metastasis, respectively. DNA and RNA hybridization capture-based NGS analysis revealed that NF1 was the most frequently mutated gene (30%) in 10 of the PMME cases. Other mutations detected in PMME included SF3B1 (20%), KRAS (10%), BRCA2 (10%), KIT (10%) and TP53 (10%) mutations. Commonly detected BRAF mutations in SKMM were not detected in PMME. Immunohistochemistry and mutation status were concordant between p53/c-Kit and TP53/KIT, respectively. Focal expression of programmed death-ligand 1 was observed in one PMME sample. The tumour mutation burden in PMME was significantly lower than that in SKMM (P = 0.030). No PMME case showed high microsatellite instability. RNA sequencing revealed a distinctive pattern with respect to RNA expression. T-cell co-stimulation differed between PMME and SKMM.

CONCLUSIONS

The RAS-mitogen-activated protein kinase pathway is one of the main pathways involved in PMME. The genetic profile of PMME was similar to that of mucosal/acral melanoma, but differed from the SKMM profile. A subset of PMMEs may contain actionable mutations. Immunotherapy seemed to be less effective for most PMMEs in this series.

The tumor genetics of acral melanoma: What should a dermatologist know?

Dermatologists stand at the gateway of individualization of classification, treatment, and outcomes of acral melanoma patients. The acral melanoma genetic landscape differs in vital ways from that of other cutaneous melanomas. These differences have important implications in understanding pathogenesis, treatment, and prognosis. The selection of molecularly targeted therapy must be adapted for acral melanoma. It is also critical to recognize that tumor development is far more complex than an isolated event, reliably treated by a medication acting on a single target. Tumors exhibit intratumor genetic heterogeneity, metastasis may have different genetic or epigenetic features than primary tumors, and tumor resistance may develop because of the activation of alternative genetic pathways. Microenvironmental, immune, and epigenetic events contribute and sustain tumors in complex ways. Treatment strategies with multiple targets are required to effectively disrupt the tumor ecosystem. This review attempts to translate the current molecular understanding of acral melanoma into digestible concepts relevant to the practice of dermatology. The focus is tumor genetics defining potentially treatable cancer pathways, contextualized within the relevant pathologic and molecular features.

Acral lentiginous melanoma: A retrospective study

BACKGROUND

Acral lentiginous melanoma (ALM) carries one of the worst prognoses among other subtypes. This malignant tumor is found on the distal limbs and is usually detected at late stages. Hereby, the authors present their experience on this melanoma subtype.

METHODS

A retrospective study was conducted. Data were extracted from patients' medical records and from phone interviews.

RESULTS

A total of 43 patients were included in the study. The main signs and symptoms disclosed by the patients were bleeding (41.9%), size greater than 6 mm (41.9%), change in size (37.2%), change in shape (30.2%), rise above the surface of the skin (27.9%), change in color (20.9%), irregular borders (16.3%), and inflammation (16.3%). The first healthcare professional consulted was a general practitioner or a dermatologist in the majority of cases (88.3%). Only 44.2% of the patients were sent by their first physician for a biopsy, whereas 30.3% were sent by the 2nd physician. 14 patients underwent biopsy within 1 month from the first appointment with a physician, while 20 patients within 3 months and 9 patients within 6 months. Only 7 patients sought medical attention in the first 3 months; 21 patients sought medical care between 3 months and one year from the appearance of the lesion, while the remaining 15 patients waited more than a year.

CONCLUSIONS

One of the major issues found in ALM is represented by the diagnostic delay; this may be due to either the patients or the physicians' failure to recognize warning signs.

BRAF, KIT, and NRAS Mutations of Acral Melanoma in White Patients

OBJECTIVES

Malignant acral melanoma (AM) is relatively infrequent in white patients. Molecular investigations have returned variable results regarding the mutational pattern. We sought to describe the mutation profile and clinicopathologic features of AM.

METHODS

We investigated BRAF, KIT, and NRAS mutational status in a series of 31 AM samples from white patients.

RESULTS

Nodular melanoma was the most common histopathologic subtype (48.4%), followed by acral lentiginous melanoma (25.8%) and superficial spreading melanoma (25.8%). BRAF, KIT, and NRAS mutational rates were 12.9%, 17.2%, and 30.0%, respectively. We observed significant associations between KIT mutational status and a thinner Breslow thickness compared with wild-type (WT) status (P = .002), NRAS mutation status and younger age compared with WT. In patients presenting at least one mutation, triple-WT patients presented metastases most frequently.

CONCLUSIONS

Although these data represent preliminary results, better knowledge of tumor biology and prognosis of AM can support the clinical approach and follow-up.

Getting under the skin: The role of CDK4/6 in melanomas

Melanoma is the deadliest type of cancer that affects the largest organ of our body, the skin. In recent years, there is an increase in the incidence and aggressiveness of melanomas. The number of treatment options has grown considerably in the past few years, leading to significant improvements in both overall and progression-free survival. One of the attractive candidates in this wave of treatment options is a cell cycle controller: cyclin-dependent kinases (CDK) 4/6 inhibitors. CDK4/6, a class of serine/threonine kinases expressed in most cell types, controls the first gap phase (G1 to S) of the cell cycle, indicating its vital importance in both normal cellular processes as well as tumorigenesis. Up to 90% of melanoma patients have genomic mutations affecting various parts of CDK4/6 pathway. Noticeably, with the help of next-generation sequencing technology, mutations with high frequency in the CDK4 pathway were also identified in relatively rare subtypes of melanoma including acral melanoma and mucosal melanoma. Therefore, CDK4/6 inhibitors have emerged as powerful and promising anticancer therapies, especially in combination treatment with immunotherapies or other targeted therapies. In this review, we will provide an overview of current scientific knowledge regarding the oncogenic properties of CDK4/6 in melanomas, we mainly discuss the latest genomic and preclinical findings of CDK4 signaling in melanoma, the progress of CDK4 inhibition as combined with other therapies for overcoming resistance and summarize recent advances from clinical trials as well as ongoing studies which gives us a better scope into the effectiveness of CDK4/6 therapy in treating malignant melanomas.

Mutation profile of primary subungual melanomas in Caucasians

Background: Specific genomic profile of cutaneous melanomas is related to UVR exposure, which exerts biological and therapeutic impact. Subungual melanoma (SUM) is an exceedingly rare disease; therefore, it is not well characterized. SUM pathogenesis is not related to UVR induced DNA damage and expected to differ from other melanoma subtypes. Our study aimed to define the mutation profile of SUM in Caucasians.

Materials and Methods: Next-generation sequencing-based genomic analysis was used to identify frequently mutated loci in 50 cancer-related genes in 31 SUM primary tumors.

Results: The most abundant mutations in SUM were found in KIT – in 13% of cases and NRAS – also in 13%, while BRAF - only in 3% of cases.

Conclusions: Our findings confirmed a high frequency of KIT and NRAS mutations in SUM, as well as a low incidence of BRAF mutations. We reported novel KRAS, CTNNB1, TP53, ERBB2, and SMAD4 mutations in SUM. Our findings provide new insights into the molecular pathogenesis of SUM.

Acral lentiginous melanoma: Basic facts, biological characteristics and research perspectives of an understudied disease

Acral lentiginous melanoma is a histological subtype of cutaneous melanoma that occurs in the glabrous skin of the palms, soles and the nail unit. Although in some countries, particularly in Latin America, Africa and Asia, it represents the most frequently diagnosed subtype of the disease, it only represents a small proportion of melanoma cases in European‐descent populations, which is partially why it has not been studied to the same extent as other forms of melanoma. As a result, its unique genomic drivers remain comparatively poorly explored, as well as its causes, with current evidence supporting a UV‐independent path to tumorigenesis. In this review, we discuss current knowledge of the aetiology and diagnostic criteria of acral lentiginous melanoma, as well as its epidemiological and histopathological characteristics. We also describe what is known about the genomic landscape of this disease and review the available biological models to explore potential therapeutic targets.

The Clinicopathological and Survival Profiles Comparison Across Primary Sites in Acral Melanoma

Background

The clinicopathological and survival profiles across primary sites in acral melanoma (AM) are still controversial and unclear.

Methods

This is a multi-center retrospective study. Clinicopathological data of AM patients diagnosed between 1 January 2000 and 31 December 2017 from 6 large tertiary hospitals in China were extracted. Chi square tests were used to compare basic characteristics between primary sites of sole, palm and nail bed. Melanoma-specific survival (MSS) differences based on primary sites were compared by log-rank tests and multivariate Cox regressions were used to identify prognostic factors for MSS.

Results

In total, 1157 AM patients were included. The sole group had a more advanced initial stage, deeper Breslow thickness, higher recurrence rate and distant metastases risk (all P < 0.05). The proportion of age < 65 years and ulceration were statistically lower in nail bed and palm groups, respectively. A total of 294 patients underwent sentinel lymph node biopsy and rates of positive SLN status had no statistical difference across primary sites. Among 701 patients with genetic profiles, the mutational frequency of BRAF, C-KIT, and PDGFRA were similar except for NRAS (higher in sole group, P = 0.0102). The median MSS of sole, nail bed and palm patients were 65.0 months, 112.0 months, and not reached, respectively (log-rank P = 0.0053). In multivariate analyses, primary site, initial stage, ulceration and recurrence were the prognostic factors for MSS in overall population, but the statistical significance varied over primary sites.

Conclusions

Substantial clinicopathological and survival heterogeneities exist across different primary sites in the AM population. Sole melanoma has worse prognosis compared with palm and nail bed subtypes.

Immunohistochemical BRAF V600E Expression and Intratumor BRAF V600E Heterogeneity in Acral Melanoma: Implication in Melanoma-Specific Survival

Acral melanoma, a distinct form of cutaneous melanoma originating in the glabrous skin of the palms, soles, and nail beds, has a different genetic background from other subtypes of cutaneous melanoma. The roles of oncogenic BRAF mutations of acral melanoma in pathogenesis and patient outcomes have not been fully elucidated. We retrieved a total of 112 patients with primary acral melanoma and checked their BRAF V600E status using immunohistochemical staining of VE1 antibody. Among these cases, 21 acral melanoma samples (18.8%) showed positive BRAF V600E staining, and of those, 11 samples (9.8%) showed a heterogeneous staining pattern, with a mixture of VE1-positive and VE1-negative cells. BRAF V600E positivity was significantly associated with thicker melanoma (p = 0.0015). There was no significant difference in clinicopathological factors between homogeneous and heterogeneous VE1-positive acral melanoma. Both patients with BRAF V600E-positive acral melanoma and those with heterogeneous BRAF V600E had significantly shorter melanoma-specific survival than those with BRAF V600E-negative melanoma in Kaplan–Meier analysis (p = 0.0283 and p = 0.0065, respectively). These findings provide novel insights into the pathobiology of acral melanoma.

Clinical and genetic analysis of melanomas arising in acral sites

STUDY AIM

Melanomas arising in acral sites are associated with a poorer prognosis than other melanoma subtypes. The aim of this study was to evaluate clinical-pathological and genetic characteristics as well as therapeutic responses of a larger cohort of patients with melanomas arising in acral sites.

METHODS

Clinical data of 134 patients with melanomas arising in acral sites from the Dept. of Dermatology Essen were collected and analysed with regard to clinicopathological characteristics and treatment responses. Genetic analysis with targeted next-generation sequencing was done on 50 samples.

RESULTS

In our cohort, BRAF (30%), NRAS (28%), TERT promoter (26%), NF1 (14%) and KIT (6%) were frequently identified mutations. Comparing tumours situated on palms and soles with melanomas arising on dorsal acral sites, a higher frequency of NRAS (39.1% versus 25%) and NF1 (17.3% versus 0%) and lower frequencies of BRAF (21.7% versus 75%) and TERT promoter (8.6% versus 50%) mutations were observed. MAPK activating mutations were identified in 64% of tumours. Overall survival was longer in patients treated with immune checkpoint inhibitors as first-line treatment than in patients receiving other systemic therapies (i.e. BRAF/MEK inhibitors and chemotherapy).

CONCLUSION

Our data suggest that the genetics of melanomas arising in acral sites varies by tumour location and may influence biological behaviour.

Frequent Occurrence of NRAS and BRAF Mutations in Human Acral Naevi

Acral naevi are benign melanocytic tumors occurring at acral sites. Occasionally they can progress to become malignant tumors (melanomas). The genetics of acral naevi have not been assessed in larger studies. In our study, a large cohort of 130 acral naevi was screened for gene mutations known to be important in other naevi and melanoma subtypes by targeted next-generation sequencing. Mutation status was correlated with clinicopathological parameters. Frequent mutations in genes activating the MAP kinase pathway were identified, including n = 87 (67%) BRAF, n = 24 (18%) NRAS, and one (1%) MAP2K1 mutations. BRAF mutations were almost exclusively V600E (n = 86, 99%) and primarily found in junctional and compound naevi. NRAS mutations were either Q61K or Q61R and frequently identified in dermal naevi. Recurrent non-V600E BRAF, KIT, NF1, and TERT promoter mutations, present in acral melanoma, were not identified. Our study identifies BRAF and NRAS mutations as the primary pathogenic event in acral naevi, however, distributed differently to those in non-acral naevi. The mutational profile of acral naevi is distinct from acral melanoma, which may be of diagnostic value in distinguishing these entities.

Clinical, Epidemiological, and Molecular Heterogeneity in Acral Melanoma

Acral melanoma comprises a poorly characterized and distinct type of melanoma, in terms of differing roles of UVR, molecular substrate, distribution among all ethnicities, and poor prognosis. Haugh et al. explore clinical, histological, and molecular aspects of acral melanomas and provide insights into the complexity of these tumors.

Early detection of acral melanoma: A review of clinical, dermoscopic, histopathologic, and molecular characteristics

Acral lentiginous melanoma is a distinct subtype of melanoma on acral skin. Patient presentation at later stages and delayed diagnosis by physicians contribute to a worse associated prognosis and survival rate. Despite our progress in understanding the key features of this disease, the diagnosis of early-stage acral melanoma is still challenging. It is essential to integrate clinical, dermoscopic, and histologic findings in the diagnosis of acral lentiginous melanoma. In addition, molecular studies can be helpful. In this review, we have summarized our current understanding of this disease entity from articles that were published between 1969 and 2018. We have outlined clinical and dermoscopic features as well as pathologic and molecular findings regarding acral melanoma and have presented an algorithm for diagnosis. Understanding and integrating these characteristics may assist clinicians in the early detection of acral melanomas.