Mosaic RASopathies concept: different skin lesions, same systemic manifestations?

BACKGROUND: Cutaneous epidermal nevi are genotypically diverse mosaic disorders. Pathogenic hotspot variants in HRAS, KRAS, and less frequently, NRAS and BRAF may cause isolated keratinocytic epidermal nevi and sebaceous nevi or several different syndromes when associated with extracutaneous anomalies. Therefore, some authors suggest the concept of mosaic RASopathies to group these different disorders. METHODS: In this paper, we describe three new cases of syndromic epidermal nevi caused by mosaic HRAS variants: one associating an extensive keratinocytic epidermal nevus with hypomastia, another with extensive mucosal involvement and a third combining a small sebaceous nevus with seizures and intellectual deficiency. Moreover, we performed extensive literature of all cases of syndromic epidermal nevi and related disorders with confirmed pathogenic postzygotic variants in HRAS, KRAS, NRAS or BRAF. RESULTS: Most patients presented with bone, ophthalmological or neurological anomalies. Rhabdomyosarcoma, urothelial cell carcinoma and pubertas praecox are also repeatedly reported. KRAS pathogenic variants are involved in 50% of the cases, especially in sebaceous nevi, oculoectodermal syndrome and encephalocraniocutaneous lipomatosis. They are frequently associated with eye and brain anomalies. Pathogenic variants in HRAS are rather present in syndromic keratinocytic epidermal nevi and phacomatosis pigmentokeratotica. CONCLUSION: This review delineates genotype/phenotype correlations of syndromic epidermal nevi with somatic RAS and BRAF pathogenic variants and may help improve their follow-up.

MITF E318K: A rare homozygous case with multiple primary melanoma.

MITF E318K moderates melanoma risk. Only five MITF E318K homozygous cases have been reported to date, one in association with melanoma. This novel report uses 3D total-body-photography (TBP) to describe the dermatological phenotype of a homozygous MITF E318K individual. The case, a 32-year-old male, was diagnosed with his first of six primary melanomas at 26 years of age. Five melanomas were located on the back and one in the groin. Two were superficial spreading. Three arose from pre-existing naevi and one was a rare naevoid melanoma. 3D-TBP revealed a high naevus count (n = 162) with pigmentation varying from light to dark. Most naevi generally (n = 90), and large (>5 mm diameter) and clinically atypical naevi specifically were located on the back where sun damage was mild. In contrast, naevi count was low (n = 25 total) on the head/neck and lower limbs where sun damage was severe. Thus, melanoma location correlated with naevi density, rather than degree of sun damage. In addition to the MITF E318K homozygosity, there was heterozygosity for four other moderate-risk variants, which may contribute to melanoma risk. Further research is warranted to explore whether melanomas in E318K heterozygous and other homozygotes coincide with regions of high naevi density as opposed to sun damage. This could inform future melanoma screening/surveillance.

Immunohistochemistry for PRAME in Dermatopathology.

ABSTRACT: Preferentially expressed antigen in melanoma (PRAME) is a tumor-associated antigen first identified in a melanoma patient and found to be expressed in most melanomas as well as in variable levels in other malignant neoplasms of epithelial, mesenchymal, or hematolymphoid lineage. Detection of PRAME expression in formalin-fixed paraffin-embedded tissue is possible by immunohistochemistry (IHC) with commercially available monoclonal antibodies. In situ and invasive melanoma frequently show a diffuse pattern of nuclear PRAME immunoreactivity which contrasts with the infrequent and typically nondiffuse staining seen in nevi. In many challenging melanocytic tumors, results of PRAME IHC and other ancillary tests correlate well, but not always: The tests are not interchangeable. Most metastatic melanomas are positive for PRAME, whereas nodal nevi are not. Numerous studies on PRAME IHC have become available in the past few years with results supporting the value of PRAME IHC as an ancillary tool in the evaluation of melanocytic lesions and providing insights into limitations in sensitivity and specificity as well as possible pitfalls that need to be kept in mind by practicing pathologists.

Genetic and phenotypic diversities of nevus spilus phenotypes: Case series and a proposed diagnostic algorithm.

Nevus spilus (NS) is composed of multiple types that characterized by a congenital hyperpigmented patch within variable even superimposed lesions originating from melanocytic lineage cells. The molecular mechanism and classification of diverse NS phenotypes remain unclear. Five children with a phenotype of NS were genotyped by the panel based on next-generation sequencing in this study. DNA from biopsies, blood samples and hair follicle were sequenced to confirm the presence of a somatic mutation. Sequencing results indicated somatic mutation in the gene of NRAS or HRAS in all biopsies from the nevi, and the pathogenic variants were not detected in the samples of blood and hair follicle. This study successfully identified the somatic mutation in five unrelated children with diverse NS phenotypes. Moreover, it provided typical images and differential diagnoses between variable NS phenotypes in clinical, pathological, and genetic features, and first proposed a clinical diagnostic algorithm that contributed to simplifying and optimizing the diagnoses and management of these overlapped diseases.

Transcriptome Analysis Identifies Oncogenic Tissue Remodeling during Progression from Common Nevi to Early Melanoma.

Early detection and treatment of melanoma, the most aggressive skin cancer, improves the median 5-year survival rate of patients from 25% to 99%. Melanoma development involves a stepwise process during which genetic changes drive histologic alterations within nevi and surrounding tissue. Herein, a comprehensive analysis of publicly available gene expression data sets of melanoma, common or congenital nevi (CN), and dysplastic nevi (DN), assessed molecular and genetic pathways leading to early melanoma. The results demonstrate several pathways reflective of ongoing local structural tissue remodeling activity likely involved during the transition from benign to early-stage melanoma. These processes include the gene expression of cancer-associated fibroblasts, collagens, extracellular matrix, and integrins, which assist early melanoma development and the immune surveillance that plays a substantial role at this early stage. Furthermore, genes up-regulated in DN were also overexpressed in melanoma tissue, supporting the notion that DN may serve as a transitional phase toward oncogenesis. CN collected from healthy individuals exhibited different gene signatures compared with histologically benign nevi tissue located adjacent to melanoma (adjacent nevi). Finally, the expression profile of microdissected adjacent nevi tissue was more similar to melanoma compared with CN, revealing the melanoma influence on this annexed tissue.

Schimmelpenning-Feuerstein-Mims syndrome induced by HRAS Gly12Ser somatic mosaic mutation: Case report and literature review.

Schimmelpenning-Feuerstein-Mims syndrome (SFMS), an epidermal nevus disease, features skin lesions including craniofacial nevus sebaceous and extracutaneous anomalies (e.g. brain, eye, and bone). Recent genetic studies implicate HRAS, KRAS, and NRAS genes in somatic mutations. Our case, a 48-year-old man, presented with nevus sebaceous on the scalp; pigmented skin lesions on the right side of his neck, back, and chest along the Blaschko lines; a history of epilepsy; and mild intellectual disability. Accordingly, SFMS was suspected. DNA analysis of nevus sebaceous skin and peripheral blood leukocytes showed a pathogenic HRAS variant NM_005343.4:c.34G > A p.(Gly12Ser) in biopsy specimens from different skin layers but not blood, indicating somatic mosaic mutation. Until now, the HRAS p.(Gly12Ser) mutation has been reported in somatic RASopathies but not SFMS. The authors report this mutation in a case of SFMS, review another 15 cases of SFMS, and discuss HRAS c.34G > A p.(Gly12Ser) somatic mutations. RAS mutations of somatic RASopathies share activating hotspot mutations found in cancers, and produce different phenotypes depending on the developmental stage at which the somatic mutations occur.

RNA analysis of tape strips to rule out melanoma in lesions clinically assessed as cutaneous malignant melanoma: A diagnostic study.

BACKGROUND: Distinguishing cutaneous malignant melanoma (CMM) from nevi can be clinically challenging. Suspicious lesions are therefore excised, resulting in many benign lesions being removed surgically to find 1 CMM. It has been proposed to use tape strip derived ribonucleic acid (RNA) to distinguish CMM from nevi. OBJECTIVE: To develop this technique further and validate if RNA profiles can rule out CMM in clinically suspicious lesions with 100% sensitivity. METHODS: Before surgical excision, 200 lesions clinically assessed as CMM were tape stripped. Expression levels of 11 genes on the tapes were investigated by RNA measurement and used in a rule-out test. RESULTS: Histopathology showed that 73 CMMs and 127 non-CMMs were included. Our test correctly identified all CMMs (100% sensitivity) based on the expression levels of 2 oncogenes, PRAME and KIT, relative to a housekeeping gene. Patient age and sample storage time were also significant. Simultaneously, our test correctly excluded CMM in 32% of non-CMM lesions (32% specificity). LIMITATIONS: Our sample contained a very high proportion of CMMs, perhaps due to inclusion during COVID-19 shutdown. Validation in a separate trial must be performed. CONCLUSION: Our results demonstrate that the technique can reduce removal of benign lesions by one-third without overlooking any CMMs.

Conceptos modernos en tumores melanocíticos / Modern Concepts in Melanocytic Tumors

Con el desarrollo de la enfermedad molecular, el diagnóstico y la comprensión de los tumores melanocíticos ha experimentado un avance descomunal en los últimos años. Esto ha significado la aparición de conceptos de difícil asimilación en el mundo clínico, el cual no está siempre en contacto directo con las técnicas genéticas de laboratorio. Al mismo tiempo, sin embargo, al clínico se le está exigiendo una terapéutica basada en muchas ocasiones en los hallazgos moleculares más recientes de un tumor melanocítico. El presente artículo explora los conceptos moleculares más recientes de la clasificación en rutas patogénicas de los tumores melanocíticos, incluidas las formas intermedias conocidas como melanocitomas, y repasa las técnicas auxiliares usadas en el estudio de estos tumores, discutiendo los resultados más complejos, sus limitaciones, y sus solapamientos (AU)

The advent of molecular pathology has fueled unprecedented advances in the diagnosis and understanding of melanocytic tumors. These advances, however, have also generated concepts that may be difficult to grasp for clinical practitioners, who are not always conversant with the array of genetic techniques employed in the laboratory. These same practitioners, however, are being increasingly called on to provide treatments that are often based on the latest molecular findings for melanocytic tumors. We review the most recent concepts in the pathway classification of melanocytic tumors, including intermediate lesions known as melanocytomas. We examine the genetic and molecular techniques used to study these tumors, look at where they overlap, and discuss their limitations and some of the most difficult-to-interpret results (AU)

[Translated article] Modern Concepts in Melanocytic Tumors / Conceptos modernos en tumores melanocíticos

The advent of molecular pathology has fueled unprecedented advances in the diagnosis and understanding of melanocytic tumors. These advances, however, have also generated concepts that may be difficult to grasp for clinical practitioners, who are not always conversant with the array of genetic techniques employed in the laboratory. These same practitioners, however, are being increasingly called on to provide treatments that are often based on the latest molecular findings for melanocytic tumors. We review the most recent concepts in the pathway classification of melanocytic tumors, including intermediate lesions known as melanocytomas. We examine the genetic and molecular techniques used to study these tumors, look at where they overlap, and discuss their limitations and some of the most difficult-to-interpret results (AU)

Con el desarrollo de la enfermedad molecular, el diagnóstico y la comprensión de los tumores melanocíticos ha experimentado un avance descomunal en los últimos años. Esto ha significado la aparición de conceptos de difícil asimilación en el mundo clínico, el cual no está siempre en contacto directo con las técnicas genéticas de laboratorio. Al mismo tiempo, sin embargo, al clínico se le está exigiendo una terapéutica basada en muchas ocasiones en los hallazgos moleculares más recientes de un tumor melanocítico. El presente artículo explora los conceptos moleculares más recientes de la clasificación en rutas patogénicas de los tumores melanocíticos, incluidas las formas intermedias conocidas como melanocitomas, y repasa las técnicas auxiliares usadas en el estudio de estos tumores, discutiendo los resultados más complejos, sus limitaciones, y sus solapamientos (AU)

Whole-exome sequencing of secondary tumors arising from nevus sebaceous revealed additional genomic alterations besides RAS mutations.

Nevus sebaceous (NS) is a congenital hamartoma associated with an increased risk of secondary neoplasms in approximately 10%-20% of patients. However, additional genomic alterations underlying tumorigenesis in NS lesions have not been clarified. We performed whole-exome sequencing of archived tumor tissues (n = 8; six basal cell carcinomas and two trichoepitheliomas) and matched germline tissues (n = 7) with from seven patients with secondary tumors arising from NS. We also analyzed NS lesions without secondary tumors (n = 8). Somatic mutations and copy number alterations (CNAs) were analyzed. We identified a median of 129 somatic mutations (corresponding to 2.6/Mb in target regions, range 26-336) for eight tumors, while a median of 118 somatic mutations (2.3/Mb, range 1-196) for eight NS lesions. Known RAS hotspot mutations were found in seven of the eight tumors (six for HRAS p.G13R and one for HRAS p.Q61R) and in six of the eight NS lesions (four for HRAS p.G13R, one for KRAS p.G12C, and one KRAS p.G12D). Except RAS mutations, several putative driver mutations were detected in tumors: TP53 p.F134L/p.R213*, MYCN p.P59L, OR2Z1 p.P167S, PTPN14 p.Q768*, and SMO p.W535L. As for CNAs, two tumors harbored copy-loss in regions encompassing PTCH1 gene. However, eight NS lesions did not harbor both putative driver mutations and CNAs. In conclusion, our study revealed that secondary tumors arising from NS harbor known RAS hotspot mutations and additional genomic alterations, including putative driver mutations and PTCH1 copy-loss. These results could help to define the high-risk group for tumor development in patients with NS and provide evidence for prophylactic resection.

Murine models of HRAS-mediated cutaneous skeletal hypophosphatemia syndrome suggest bone as the FGF23 excess source.

Cutaneous skeletal hypophosphatemia syndrome (CSHS) is a mosaic RASopathy characterized by the association of dysplastic skeletal lesions, congenital skin nevi of epidermal and/or melanocytic origin, and FGF23-mediated hypophosphatemia. The primary physiological source of circulating FGF23 is bone cells. However, several reports have suggested skin lesions as the source of excess FGF23 in CSHS. Consequently, without convincing evidence of efficacy, many patients with CSHS have undergone painful removal of cutaneous lesions in an effort to normalize blood phosphate levels. This study aims to elucidate whether the source of FGF23 excess in CSHS is RAS mutation-bearing bone or skin lesions. Toward this end, we analyzed the expression and activity of Fgf23 in two mouse models expressing similar HRAS/Hras activating mutations in a mosaic-like fashion in either bone or epidermal tissue. We found that HRAS hyperactivity in bone, not skin, caused excess of bioactive intact FGF23, hypophosphatemia, and osteomalacia. Our findings support RAS-mutated dysplastic bone as the primary source of physiologically active FGF23 excess in patients with CSHS. This evidence informs the care of patients with CSHS, arguing against the practice of nevi removal to decrease circulating, physiologically active FGF23.

Verrucous epidermal nevus as a manifestation of a type 2 mosaic PTEN mutation in Cowden syndrome.

Linear Cowden nevus, also known as linear PTEN nevus, is a type of epidermal nevus, first described in 2007, which is seen in patients with PTEN hamartoma tumor syndrome. It is considered to be a type 2 form of segmental mosaicism, and we suggest that it has certain clinical features that distinguish it from epidermal nevi seen in similar conditions, such as Proteus syndrome. We present a case of linear Cowden nevus in a 4-year-old boy and review the literature.

A possible role for second-hit postzygotic GJB2 mutation in porokeratotic eccrine ostial and dermal duct nevus.

Porokeratotic eccrine ostial and dermal duct nevus (PEODDN) is a rare type of epidermal nevus involving the eccrine acrosyringia. It typically presents as asymptomatic linear keratotic papules and plaques along the lines of Blaschko and predominantly affects the extremities. This disease has recently been linked to somatic mutations within the GJB2 locus. Only four GJB2 mutations have been previously documented for PEODDN, and the underlying genetic basis remains inconclusive. Herein, we report an 18-year-old female with a hyperkeratotic plaque on the dorsa of the proximal interphalangeal joint of her right ring finger, as well as multiple small hyperkeratotic papules linearly distributed on the lateral sides of her fingers occurring since birth. Histopathological results revealed prominent parakeratotic cornoid lamella-like tiers at the opening of the eccrine secretory ducts. Whole-exome sequencing of the affected skin tissue revealed a heterozygous germline mutation and a postzygotic somatic mutation in GJB2. In summary, this study presents a case of PEODDN with compound heterozygous mutations in GJB2, which broadens the genetic spectrum of this disease entity and implies a possible role for second-hit mutations in the pathogenesis of PEODDN.

Etiological identification of recurrent male fatality due to a novel NSDHL gene mutation using trio whole-exome sequencing: A rare case report and literature review.

BACKGROUND: Congenital hemidysplasia with ichthyosiform nevus and limb defects (CHILD) syndrome is a rare X-linked dominant, lethal male disorder caused by mutations to the NSDHL (NAD(P)H steroid dehydrogenase-like protein) gene. It primarily exhibits strictly unilateral congenital hemidysplasia with ichthyosiform erythroderma and ipsilateral limb defects in female individuals. METHODS: A Chinese couple suffering from recurrent spontaneous abortion in male fetuses was enrolled in this study. Chromosomal microarray analysis and whole-exome sequencing were performed for genetic etiological diagnosis. RESULTS: A 33-year-old pregnant woman with recurrent spontaneous abortion was experiencing her third pregnancy with a male embryo. In this pregnancy, a miscarriage occurred at a gestational age of 10+6  weeks with no copy number variants. However, a novel mutation c.790-6C>T in the NSDHL gene was observed in the fetus through whole-exome sequencing (WES). Parental verification indicated that the NSDHL gene variant was inherited from the mother. Additionally, the variant in the NSDHL gene was absent in her subsequent pregnancy with a female fetus. CONCLUSION: In this study, we detected c.790-6C>T, a novel variant in the NSDHL gene that results in recurrent miscarriage in males. Our study may broaden the scope of research on the NSDHL gene in CHILD syndrome and strengthens the application value of WES for the genetic etiological identification of recurrent miscarriage.

Dysplastic nevus part II: Dysplastic nevi: Molecular/genetic profiles and management.

Dermatologists frequently see patients with clinically atypical nevi and dermatopathologists interpret histologically dysplastic nevi on a near-daily basis, but there is great variability in the definition and management of such lesions. This part of the CME review focuses on information published since the previous comprehensive review (2012), with emphasis on molecular and genetic attributes of histologically dysplastic nevi and clinical management.

Epidermal nevus syndrome with the mutation of PTCH1 gene and cerebral infarction: a case report and review of the literature.

BACKGROUND: Epidermal nevus syndrome is a group of congenital neuroectodermal and/or mesodermal disorders characterized by the epidermal nevi in common association with cerebral, eye, skeletal, cardiovascular, and renal abnormalities. Epidermal nevus syndrome is a rare syndrome, and epidermal nevus syndrome with the mutation of PTCH1 gene and cerebral infarction is even rarer and has not been reported to the best of our knowledge. CASE PRESENTATION: We report the case of a 10-month-old Chinese female patient who presented to our pediatric neurologic department, University of Wenzhou medical teaching Hospital, Hangzhou. She has mobility disorders on the right limbs and recurrent seizures. She had congenital disorder accompanied by brownish-black and verrucose plaques on the right side of the face as well as extensive brownish-black plaques and brown nevi on the right side of the trunk and the right arm. Epidermal nevus syndrome was diagnosed on the basis of her symptoms. Somatic sebaceous nevi and hypoplastic defects of skin, cerebra, eyes, skeleton, and cardiovascular and renal system were observed. However, in addition to the typical clinical characteristics, the patient also has a mutation (c.109G > T) in PTCH1 gene and cerebral infarction. We present a novel case report and literature review. CONCLUSION: To our knowledge, epidermal nevus syndrome with a mutation of PTCH1 gene and cerebral infarction has not been reported previously. This case report may contribute to characterizing the phenotype of epidermal nevus syndrome, help clinicians be aware of the association of this condition with PTCH1 gene and cerebral infarction, raise clinical suspicion, and improve early therapy.

Inflammatory linear verrucous epidermal nevus (ILVEN) encompasses a spectrum of inflammatory mosaic disorders.

BACKGROUND: Inflammatory linear verrucous epidermal nevus (ILVEN) is a rare skin disease characterized by pruritic erythematous scaly plaques distributed along the lines of Blaschko. Two cases of ILVEN with CARD14 mutations and one case with a GJA1 mutation have been previously reported. OBJECTIVE: To elucidate the genetic cause of a cohort of patients diagnosed based on clinical and histopathological evaluation with ILVEN. METHODS: We recruited patients diagnosed with ILVEN based on clinical and histopathological criteria. Exome sequencing of affected skin with or without blood/saliva was performed and germline and somatic pathogenic variants were identified. RESULTS: Five patients were enrolled. All had skin lesions from birth or early childhood. Two patients developed psoriasis vulgaris after the diagnosis of ILVEN. The first had a germline heterozygous CARD14 mutation and a post-zygotic hotspot mutation in KRT10. The histopathologic evaluation did not show epidermolytic hyperkeratosis. The second had a post-zygotic hotspot mutation in HRAS. Her ILVEN became itchy once psoriasis developed. One patient was re-diagnosed with linear porokeratosis based on a germline mutation in PMVK and a post-zygotic second-hit mutation. Two patients were re-diagnosed with congenital hemidysplasia with ichthyosiform nevus and limb defect nevus based on germline NSDHL mutations. CONCLUSION: ILVEN is a clinical descriptor for a heterogenous group of mosaic inflammatory disorders. Genetic analysis has the potential to more precisely categorize ILVEN and permits pathogenesis-directed therapies in some cases.