Intramuscular fast-flow vascular anomaly contains somatic MAP2K1 and KRAS mutations

Sotorasib for Vascular Malformations Associated with KRAS G12C Mutation

KRAS gain-of-function mutations are frequently observed in sporadic arteriovenous malformations. The mechanisms underlying the progression of such KRAS-driven malformations are still incompletely understood, and no treatments for the condition are approved. Here, we show the effectiveness of sotorasib, a specific KRAS G12C inhibitor, in reducing the volume of vascular malformations and improving survival in two mouse models carrying a mosaic Kras G12C mutation. We then administered sotorasib to two adult patients with severe KRAS G12C-related arteriovenous malformations. Both patients had rapid reductions in symptoms and arteriovenous malformation size. Targeting KRAS G12C appears to be a promising therapeutic approach for patients with KRAS G12C-related vascular malformations. (Funded by the European Research Council and others.).

Somatic RIT1 delins in arteriovenous malformations hyperactivate RAS-MAPK signaling amenable to MEK inhibition

Arteriovenous malformations (AVM) are benign vascular anomalies prone to pain, bleeding, and progressive growth. AVM are mainly caused by mosaic pathogenic variants of the RAS-MAPK pathway. However, a causative variant is not identified in all patients. Using ultra-deep sequencing, we identified novel somatic RIT1 delins variants in lesional tissue of three AVM patients. RIT1 encodes a RAS-like protein that can modulate RAS-MAPK signaling. We expressed RIT1 variants in HEK293T cells, which led to a strong increase in ERK1/2 phosphorylation. Endothelial-specific mosaic overexpression of RIT1 delins in zebrafish embryos induced AVM formation, highlighting their functional importance in vascular development. Both ERK1/2 hyperactivation in vitro and AVM formation in vivo could be suppressed by pharmacological MEK inhibition. Treatment with the MEK inhibitor trametinib led to a significant decrease in bleeding episodes and AVM size in one patient. Our findings implicate RIT1 in AVM formation and provide a rationale for clinical trials with targeted treatments.

Extracranial Vascular Anomalies Driven by RAS/MAPK Variants: Spectrum and Genotype-Phenotype Correlations

BACKGROUND

We aimed to correlate alterations in the rat sarcoma virus (RAS)/mitogen-activated protein kinase pathway in vascular anomalies to the clinical phenotype for improved patient and treatment stratification.

METHODS AND RESULTS

This retrospective multicenter cohort study included 29 patients with extracranial vascular anomalies containing mosaic pathogenic variants (PVs) in genes of the RAS/mitogen-activated protein kinase pathway. Tissue samples were collected during invasive treatment or clinically indicated biopsies. PVs were detected by the targeted sequencing of panels of genes known to be associated with vascular anomalies, performed using DNA from affected tissue. Subgroup analyses were performed according to the affected genes with regard to phenotypic characteristics in a descriptive manner. Twenty-five vascular malformations, 3 vascular tumors, and 1 patient with both a vascular malformation and vascular tumor presented the following distribution of PVs in genes: Kirsten rat sarcoma viral oncogene (n=10), neuroblastoma ras viral oncogene homolog (n=1), Harvey rat sarcoma viral oncogene homolog (n=5), V-Raf murine sarcoma viral oncogene homolog B (n=8), and mitogen-activated protein kinase kinase 1 (n=5). Patients with RAS PVs had advanced disease stages according to the Schobinger classification (stage 3-4: RAS, 9/13 versus non-RAS, 3/11) and more frequent progression after treatment (RAS, 10/13 versus non-RAS, 2/11). Lesions with Kirsten rat sarcoma viral oncogene PVs infiltrated more tissue layers compared with the other PVs including other RAS PVs (multiple tissue layers: Kirsten rat sarcoma viral oncogene, 8/10 versus other PVs, 6/19).

CONCLUSIONS

This comparison of patients with various PVs in genes of the RAS/MAPK pathway provides potential associations with certain morphological and clinical phenotypes. RAS variants were associated with more aggressive phenotypes, generating preliminary data and hypothesis for future larger studies.

Arteriovenous malformation Map2k1 mutation affects vasculogenesis

Somatic activating MAP2K1 mutations in endothelial cells (ECs) cause extracranial arteriovenous malformation (AVM). We previously reported the generation of a mouse line allowing inducible expression of constitutively active MAP2K1 (p.K57N) from the Rosa locus (R26GT-Map2k1-GFP/+) and showed, using Tg-Cdh5CreER, that EC expression of mutant MAP2K1 is sufficient for the development of vascular malformations in the brain, ear, and intestines. To gain further insight into the mechanism by which mutant MAP2K1 drives AVM development, we induced MAP2K1 (p.K57N) expression in ECs of postnatal-day-1 pups (P1) and investigated the changes in gene expression in P9 brain ECs by RNA-seq. We found that over-expression of MAP2K1 altered the transcript abundance of > 1600 genes. Several genes had > 20-fold changes between MAP2K1 expressing and wild-type ECs; the highest were Col15a1 (39-fold) and Itgb3 (24-fold). Increased expression of COL15A1 in R26GT-Map2k1-GFP/+; Tg-Cdh5CreER+/- brain ECs was validated by immunostaining. Ontology showed that differentially expressed genes were involved in processes important for vasculogenesis (e.g., cell migration, adhesion, extracellular matrix organization, tube formation, angiogenesis). Understanding how these genes and pathways contribute to AVM formation will help identify targets for therapeutic intervention.

Intramuscular capillary-type hemangioma: Diagnosis, treatment, and outcomes. A French multicentric retrospective study of 66 cases

PURPOSE

Intramuscular capillary-type hemangiomas (ICTHs) are rare entities, belonging to the group of intramuscular "hemangiomas." The diagnosis remains challenging. We aimed to assess the diagnostic criteria, treatments and outcomes of ICTHs.

METHODS

This retrospective study collected all cases of ICTH followed up in 9 French hospital centers, reviewed by an adjudication expert group.

RESULTS

Among 133 patients screened, 66 with ICTH were included. The median age of patients at diagnosis was 28.0 years, interquartile range (21.0---36.0). The lesion, mainly presenting as a gradually increasing mass (83.9%), was painless (88.9%) and was located in the head and neck (42.4%). MRI (available in all cases) mainly revealed a well-delineated lesion, isointense to the muscle on T1-weighted images, with enhancement after contrast injection; hyperintense on T2-weighted images; and containing flow voids. Among the 66 cases, 59 exhibited typical ICTH features and 7 shared some imaging features with arteriovenous malformations. These latter were larger than typical ICTHs and more painful and appeared on imaging as less well delimited and more heterogeneous tissue masses, with larger tortuous afferent arteries, earlier draining vein opacification and mild arteriovenous shunting. We propose to name these lesions arteriovenous malformation (AVM)-like ICTH. Pathological reports were similar in typical and AVM-like ICTH, showing capillary proliferation with mainly small-size vessels, negative for GLUT-1 and positive for ERG, AML, CD31 and CD34, with low Ki67 proliferation index (<10%), and adipose tissue. The most frequent treatment for ICTH was complete surgical resection (17/47, 36.2%), preceded in some cases by embolization, which led to complete remission.

CONCLUSIONS

ICTH can be diagnosed on MRI when it is typical. Biopsy or angiography are required for atypical forms.

Characteristics, Natural Course and Treatment of Intramuscular Capillary-type Haemangioma: A Systematic Literature Review

Intramuscular capillary-type haemangiomas (ICTH) are rare vascular anomalies that can easily be misdiagnosed as other entities. A systematic review was performed of all cases of ICTH in the literature since its first description in 1972. An adjudication committee reviewed cases to include only ICTHs. Among 1,143 reports screened, 43 were included, involving 75 patients. The most frequent differential diagnosis was intramuscular venous malformations. The mean age of patients at diagnosis was 21.2 years. ICTH was mainly described as a gradually increasing mass (81.8%), painless (73.9%), that could occur anywhere in the body but most frequently on the head and neck (44.0%). Magnetic resonance imaging (MRI) was mainly used for diagnosis (69.1%) and displayed specific features. The most frequent treatment was complete surgical removal (73.9%), which could be preceded by embolization, and led to complete remission without recurrence in all but 1 case.

High-depth next-generation sequencing panel testing in the evaluation of arteriovenous malformations

Arteriovenous malformations (AVMs) are vascular lesions in which an overgrowth of blood vessels of varying sizes develops with one or more direct connections between the arterial and venous circulation. We performed a retrospective review of a cohort of 54 patients with AVMs referred to our clinical genomic laboratory for high-depth next-generation sequencing (NGS) panel of Disorders of Somatic Mosaicism (DoSM). Thirty-seven of 54 patients were female (68.5%). Among the 54 cases, 37 (68.5%) cases had pathogenic and/or likely pathogenic (P/LP) variants identified, two cases (3.7%) had variants of uncertain clinical significance, and the remaining 15 cases (27.8%) had negative results. MAP2K1 variants were found in 12 cases, followed by eight cases with KRAS variants and seven with TEK variants, and the remainder being identified in several other genes on the panel. Among the 37 positive cases, 32 cases had somatic alterations only; the remaining five cases had at least one germline P/LP variant, including four cases with PTEN and one with RASA1. Of note, two cases had the unexpected co-existence of two P/LP variants. In summary, this study illustrated the molecular diagnostic yield (68.5%) of this cohort of patients with a clinical indication of AVMs by our high-depth DoSM NGS panel.

Advances in droplet digital polymerase chain reaction on microfluidic chips

The PCR technique has been known to the general public since the pandemic outbreak of COVID-19. This technique has progressed through three stages: from simple PCR to real-time fluorescence PCR to digital PCR. Among them, the microfluidic-based droplet digital PCR technique has attracted much attention and has been widely applied due to its advantages of high throughput, high sensitivity, low reagent consumption, low cross-contamination, and absolute quantification ability. In this review, we introduce various designs of microfluidic-based ddPCR developed within the last decade. The microfluidic-based droplet generation methods, thermal cycle strategies, and signal counting approaches are described, and the applications in the fields of single-cell analysis, disease diagnosis, and pathogen detection are introduced. Further, the challenges and prospects of microfluidic-based ddPCR are discussed. We hope that this review can contribute to the further development of the microfluidic-based ddPCR technique.

Endothelial cell expression of mutant Map2k1 causes vascular malformations in mice

Extracranial arteriovenous malformation (AVM) is a congenital vascular anomaly causing disfigurement, bleeding, ulceration, and pain. Most lesions are associated with somatic MAP2K1 activating mutations in endothelial cells (ECs). The purpose of this study was to determine if EC expression of mutant activated MAP2K1 is sufficient to produce vascular malformations in mice. We generated mice with a ROSA26 allele containing a lox-stop-lox gene trap (GT), Map2k1 cDNA with an activating p.K57N missense mutation, an internal ribosomal entry site, and green fluorescent protein cDNA (R26GT-Map2k1-GFP). We expressed mutant MAP2K1 and GFP in ECs of fetal and newborn mice using Tg-Cdh5Cre or Tg-Cdh5CreER alleles. Tg-Cdh5Cre+/-;R26GT-Map2k1-GFP/+ animals that express mutant MAP2K1 in ECs in utero developed diffuse vascular abnormalities and died by embryonic (E) day 16.5. Tg-Cdh5CreER+/-;R26GT-Map2k1-GFP/+ animals in which mutant MAP2K1 expression was induced in ECs by tamoxifen at postnatal (P) day 1 developed vascular malformations in the brain, ear, and intestines by P23. The lesions consisted of abnormal networks of blood vessels containing recombined and non-recombined ECs. In conclusion, expression of MAP2K1 p.K57N is sufficient to cause vascular malformations in mice. This model can be used to study the malformation process and for pre-clinical pharmacologic studies.

Trametinib as a promising therapeutic option in alleviating vascular defects in an endothelial KRAS-induced mouse model

Somatic activating Kirsten rat sarcoma viral oncogene homologue (KRAS) mutations have been reported in patients with arteriovenous malformations. By producing LSL-Kras (G12D); Cdh5 (PAC)-CreERT2 [iEC-Kras (G12D*)] mice, we hoped to activate KRAS within vascular endothelial cells (ECs) to generate an arteriovenous malformation mouse model. Neonatal mice were treated daily with tamoxifen from postnatal (PN) days 1-3. Mortality and phenotypes varied amongst iEC-Kras (G12D*) pups, with only 31.5% surviving at PN14. Phenotypes (focal lesions, vessel dilations) developed in a consistent manner, although with unpredictable severity within multiple soft tissues (such as the brain, liver, heart and brain). Overall, iEC-Kras (G12D*) pups developed significantly larger vascular lumen areas compared with control littermates, beginning at PN8. We subsequently tested whether the MEK inhibitor trametinib could effectively alleviate lesion progression. At PN16, iEC-Kras (G12D*) pup survival improved to 76.9%, and average vessel sizes were closer to controls than in untreated and vehicle-treated mutants. In addition, trametinib treatment helped normalize iEC-Kras (G12D*) vessel morphology in PN14 brains. Thus, trametinib could act as an effective therapy for KRAS-induced vascular malformations in patients.

How we approach genetics in the diagnosis and management of vascular anomalies

Vascular anomalies are a heterogeneous group of disorders that are currently classified based on their clinical and histological characteristics. Over the past decade, there have been significant advances in molecular genetics that have led to identification of genetic alterations associated with vascular tumors, vascular malformations, and syndromes. Here, we describe known genetic alterations in vascular anomalies, discuss when and how to test, and examine how identification of causative genetic mutations provides for better management of these disorders through improved understanding of their pathogenesis and increasing use of targeted therapeutic agents in order to achieve better outcomes for our patients.

VEGF Pathway Gene Expression Profile of Proliferating versus Involuting Infantile Hemangiomas: Preliminary Evidence and Review of the Literature

Background. Infantile hemangiomas may have unexpected behavior. Initial regression (spontaneously or drug-induced) may be followed by unexplained recurrences. At this moment, there are no well-established criteria to predict infantile hemangioma reccurrences. Methods. We compared the VEGF pathway gene expression profile for one case of involuting infantile hemangioma versus one case of recurrent proliferative infantile hemangioma using TaqMan Array. Results. We found ten genes upregulated for both involuting and recurrent proliferative hemangiomas: ACTB, KRAS, MAP2K1, HRAS, NOS3, BAD, HSPB1, HPRT1, GUSB, and CASP9. Thirteen genes were downregulated for both involuting and proliferative hemangiomas: FIGF, ACTG1, GRB2, MAPKAPK2, ACTG2, MAP2K2, MAPK3, HSP90AA1, MAP2K6, NRAS, ACTA1, KDR, and MAPK1. Three genes showed divergent expression between proliferating and involuting hemangiomas. Proliferating hemangioma had MAPK14 and AKT1 gene upregulation and ACTA2 downregulation. Involuting infantile hemangioma was characterized by ACTA2 upregulation and AKT1 and MAPK14 downregulation. Conclusions. Three genes, AKT1, p38/MAPK14, and ACTA2, were found to have divergent expression in proliferating and involuting infantile hemangiomas. Excepting AKT1, which was mentioned in the last ISSVA classification (strictly related to Proteus Syndrome), none of the other genes were reported. An accurate gene expression profile mapping of infantile hemangiomas together with a gene expression-based hemangioma classification is stringently needed.

The Challenges of Upper Extremity Intramuscular Hemangioma: a Case Study and Systematic Review

BACKGROUND

Intramuscular hemangiomas (IMHs) are rare, benign vascular tumors, comprising 0.8% of all hemangiomas. Upper extremity (UE) IMHs pose diagnostic and therapeutic challenges given their rarity, invasive nature, and potential for neurovascular involvement. We report a comprehensive systematic review of UE IMH management and a challenging case report.

METHODS

A systematic review was performed using PRISMA guidelines. Electronic databases were used to identify papers describing UE IMHs through 2019. Patient demographics, clinical presentation, management, complications, and outcomes were reviewed. Based on operative timing, cases were categorized as either "primary" (excision performed at initial diagnosis) or "secondary" (excision performed after failure of conservative treatment).

RESULTS

Eighteen articles encompassing 25 patients were included in our systematic review. Of those, 18 underwent primary excision and 7 underwent secondary excision. The majority involved the forearm or antecubital region. Complete excision, evaluated by gross examination or pathology, was reported in all primary cases and 71% secondary cases. Primary excisions demonstrated smaller mass size (19.4cm2 versus 165.3cm2) and superior reported functional outcomes (100% versus 33%). Complications were reported in 5% of the primary excisions compared to 71% of the secondary excisions, where 1 complication was a fatal hematoma.

CONCLUSION

The literature concerning UE IMH is limited to mostly case reports and several case series with the potential risk of bias. With careful dissection and microsurgical technique, wide local excision followed by complete reconstruction can be successfully performed at initial diagnosis for UE IMHs. At early stages, smaller lesion size significantly reduces the risk of functional impairment and complications.

Parkes Weber syndrome with lymphedema caused by a somatic KRAS variant

Parkes Weber syndrome is a vascular malformation overgrowth condition typically involving the legs. Its main features are diffuse arteriovenous fistulas and enlargement of the limb. The condition has been associated with pathogenic germline variants in RASA1 and EPHB4. We report two individuals with Parkes Weber syndrome of the leg and primary lymphedema containing a somatic KRAS variant (NM_004985.5:c.35G > A; p.Gly12Asp). KRAS variants, which cause somatic intracranial and extracranial arteriovenous malformations, also result in Parkes Weber syndrome with lymphatic malformations.

Newcomers in Vascular Anomalies

Vascular anomalies are composed of tumors and malformations and with overlapping histologies, thus are often misdiagnosed or labeled with imprecise terminology. Lesions are common and usually diagnosed during infancy or childhood; the estimated prevalence is 4.5%. Vascular tumors rapidly enlarge postnatally and demonstrate endothelial proliferation. Malformations are errors in vascular development with stable endothelial turnover; they are typically named based on the primary vessel that is malformed (capillary, arterial, venous, lymphatic). This article reviews the pathologic and molecular genetic characteristics for select recently described vascular anomalies.

Arteriovenous Malformations-Current Understanding of the Pathogenesis with Implications for Treatment

Arteriovenous malformations are a vascular anomaly typically present at birth, characterized by an abnormal connection between an artery and a vein (bypassing the capillaries). These high flow lesions can vary in size and location. Therapeutic approaches are limited, and AVMs can cause significant morbidity and mortality. Here, we describe our current understanding of the pathogenesis of arteriovenous malformations based on preclinical and clinical findings. We discuss past and present accomplishments and challenges in the field and identify research gaps that need to be filled for the successful development of therapeutic strategies in the future.

Functional assessment of two variants of unknown significance in TEK by endothelium-specific expression in zebrafish embryos

Vascular malformations are most often caused by somatic mutations of the PI3K/mTOR and the RAS signaling pathways, which can be identified in the affected tissue. Venous malformations commonly harbor PIK3CA and TEK mutations, whereas arteriovenous malformations are usually caused by BRAF, RAS, or MAP2K1 mutations. Correct identification of the underlying mutation is of increasing importance, since targeted treatments are becoming more and more relevant, especially in patients with extensive vascular malformations. However, variants of unknown significance are often identified and their pathogenicity and response to targeted therapy cannot be precisely predicted. Here we show, that zebrafish embryos can be used to rapidly assess the pathogenicity of novel variants of unknown significance in TEK, encoding for the receptor TIE2, present on endothelial cells of venous malformations. Endothelium-specific overexpression of TEK mutations leads to robust induction of venous malformations whereas MAP2K1 mutations cause arteriovenous malformations in our zebrafish model. TEK mutations are often found as double mutations in cis; using our model, we show that double mutations have an additive effect in inducing venous malformations compared to the respective single variants. The clinically established mTOR-inhibitor sirolimus (rapamycin) efficiently abrogates the development of venous malformations in this zebrafish model. In summary, endothelium-specific overexpression of patient-derived TEK variants in the zebrafish model allows assessment of their pathogenic significance as well as testing of candidate drugs in a personalized and mutation-specific approach.

Somatic Mosaicism in the Pathogenesis of de novo Cerebral Arteriovenous Malformations: A Paradigm Shift Implicating the RAS-MAPK Signaling Cascade

Cerebral arteriovenous malformations (AVMs) are leading causes of lesional hemorrhagic stroke in both the pediatric and young adult population, with sporadic AVMs accounting for the majority of cases. Recent evidence has identified somatic mosaicism in key proximal components of the RAS-MAPK signaling cascade within endothelial cells collected from human sporadic cerebral AVMs, with early preclinical models supporting a potential causal role for these mutations in the pathogenesis of these malformations. Germline mutations that predispose to deregulation of the RAS-MAPK signaling axis have also been identified in hereditary vascular malformation syndromes, highlighting the key role of this signaling axis in global AVM development. Herein, we review the most recent genomic and preclinical evidence implicating somatic mosaicism in the RAS-MAPK signaling pathway in the pathogenesis of sporadic cerebral AVMs. Also, we review evidence for RAS-MAPK dysregulation in hereditary vascular malformation syndromes and present a hypothesis suggesting that this pathway is central for the development of both sporadic and syndrome-associated AVMs. Finally, we examine the clinical implications of these recent discoveries and highlight potential therapeutic targets within this signaling pathway.

Surgical Management of Intramuscular Venous Malformations

BACKGROUND

Intramuscular venous malformations, often erroneously called "intramuscular hemangiomas," present to pediatric orthopaedic surgeons either as a differential diagnosis of tumor or as a cause of muscle pain. Treatment options include injection sclerotherapy or surgery. There is some literature to indicate that sclerotherapy can reduce pain, but little evidence on the effectiveness of surgery. The primary aim of this study was to evaluate the efficacy of surgical resection for intramuscular venous malformations, with a secondary aim to evaluate the natural history and presentation of intramuscular venous malformations to improve clinician understanding of this condition.

METHODS

A retrospective chart analysis was performed of cases identified from a vascular anomalies database from January 2004 and December 2018. Primary outcome was change in preoperative and postoperative pain. Natural history of the lesion was assessed, including age when the lesion was first noticed, when it became painful, and when it required treatment.

RESULTS

Fifty-four cases were identified in the study period of which 40 underwent surgery. Pain improved in 36 of 39 patients (92.3%) who had pain before surgery and 29 (74.4%) were pain free after surgery. All 13 patients who required whole muscle excision to resect the lesion experienced an improvement in pain and 10 (76.9%) were pain free. A history of previous intervention, with surgery or sclerotherapy showed a trend towards less successful surgical outcomes. Patients presented across a wide age range from infancy to adulthood, but the most common presentation was pain with exercise between 9 and 16 years of age, with presence of a mass in about half of cases.

CONCLUSIONS

Surgery, when performed by a surgeon with appropriate experience, is an effective first-line treatment for painful intramuscular venous malformations, offering pain relief in the majority of cases. Magnetic resonance imaging and ultrasound are diagnostic in most cases. The majority of lesions are resectable, meaning they can be removed with a margin leaving a functional limb. Sometimes resection of a whole muscle is required.

LEVEL OF EVIDENCE

Level IV-case series.

[Classification of vascular tumours and vascular malformations. Contribution of the ISSVA 2014/2018 classification]

The study of vascular anomalies, "angiomas", vascular tumours and vascular malformations is made difficult by the great variety and confusion of the names used in the literature for these diseases, some of which are rare. The great merit of the classification proposed by the International Society for the Study of Vascular Anomalies (ISSVA), adopted in 2014 and modified in 2018, is to propose a unambiguous nomenclature and to try to group these lesions in a logical way, contrasting with the lists of the usual "classifications". This classification is based on the distinction between proliferative lesions (tumours and reactive lesions) and those which are due to a congenital anomaly of vascular morphogenesis (vascular malformations). It incorporates recent data on the molecular causes of these diseases. The major groups of lesions recognised in this classification will be presented and some lesions of interest briefly discussed. This classification aims to be usable by all medical specialties and applicable to all tissues and organs, even if efforts are still needed to integrate organ-specific names in order to unify the nomenclature and eliminate confusion. Even if it does not solve all the problems in this complex field, the unification of the nomenclature is a major contribution of this classification and pathologists are strongly encouraged to refer to it in daily practice.

Update on extracranial arteriovenous malformations: A staged multidisciplinary approach

Arteriovenous malformations (AVMs) are vascular lesions that are thought to arise from congenital errors during development of vessels resulting in abnormal connections between arteries and veins. Though most AVMs develop in the brain or spinal cord, they can occur anywhere in the body. These extracranial or peripheral AVMs have a predilection for the head, neck, and limbs. Since these malformations infiltrate normal soft tissue, management requires selective treatment with preservation of normal surrounding architecture. Therefore, they are best addressed through a staged multimodal and multidisciplinary approach, using a combination of different laser, interstitial, intravascular and surgical techniques to specifically target anomalous vessels. The goal of treatment is overall disease improvement and symptom control with interventions that do not result in outcomes worse than the disease itself. Recently, the discovery of somatic and germline mutations in peripheral AVMs have contributed to a better understanding of the pathophysiology, resulting in promising new pharmacologic treatments. Recent evidence suggests that adjuvant medical therapy can enhance and sustain interventional and/or surgical outcomes. Herein we describe how a new understanding of the etiology and physiology of extracranial AVM provides guidance to current treatment approaches.

Arteriovenous malformation phenotype resembling congenital hemangioma contains KRAS mutations

Extracranial arteriovenous malformation (AVM) is most commonly caused by a somatic mutation in MAP2K1. We report two patients with vascular anomalies that had an unclear clinical diagnosis most consistent with either an AVM or congenital hemangioma. Lesions were cutaneous, reddish-purple with telangiectasias, present at birth, and had defined borders. Histopathology indicated AVM and both lesions contained somatic KRAS mutations. A rare AVM phenotype exists that shares clinical features with congenital hemangioma.

Novel genetic alteration in congenital melanocytic nevus: MAP2K1 germline mutation with BRAF somatic mutation

Congenital melanocytic nevus (CMN) represent a benign proliferative skin disease in the epidermis and dermis. CMN are historically known to be associated with activating NRAS or BRAF mutations. Melanoma frequently harbors the BRAF p.Val600Glu mutation, which is also commonly found in benign nevi. A recent study reported mutation of MAP2K1, a downstream effector of the RAS-RAF-MEK pathway, in melanoma with an overall frequency of 8%. Later, in 2019, Jansen P detected one activating MAP2K1 mutation in acral nevi. However, it is unknown whether MAP2K1 mutations are common in CMN, and how MAP2K1 contributes to the pathogenesis of CMN remains to be determined.In this study, we report one patient clinically and histologically diagnosed with CMN, with the MAP2K1 germline mutation and a BRAF p.Val600Glu somatic hit in the lesion. To the best of our knowledge, this is the first report of the coexistence of mutated BRAF and MAP2K1 in CMN, which may suggest that MAP2K1 mutations contribute to the occurrence and development of nevus expanding our knowledge of the genetics of CMN.