Frequency of microsatellite instability in unselected sebaceous gland neoplasias and hyperplasias

Sebaceous gland neoplasias are the cutaneous manifestation of the Muir-Torre syndrome, which is known to be a phenotypical variant of hereditary nonpolyposis colorectal cancer. Both hereditary nonpolyposis colorectal cancer and Muir-Torre syndrome are caused by inherited DNA mismatch repair defects. As a prominent molecular genetic feature, all tumors associated with a DNA mismatch repair defect exhibit high microsatellite instability. So far, the frequency of DNA mismatch repair defects in patients selected solely on the basis of a sebaceous gland tumor has never been determined. In order to estimate this frequency, we assessed microsatellite instability with up to 10 microsatellite markers in a newly collected unselected series of 25 sebaceous gland neoplasias (six sebaceous adenomas, 16 sebaceous epitheliomas, three sebaceous carcinomas) in comparison to 32 sebaceous gland hyperplasias from unrelated patients. As many as 15 of the 25 sebaceous gland neoplasias (60%), but only one of the 32 sebaceous gland hyperplasias (3%), exhibited high microsatellite instability. Thus, in our study, the majority of patients with a sebaceous gland neoplasia in contrast to patients with a sebaceous gland hyperplasia are highly suspicious for an inherited DNA mismatch repair defect. On the basis of the subsequently collected tumor histories, nine of the 15 patients with a high microsatellite unstable sebaceous gland neoplasia were identified to have Muir-Torre syndrome. In none of these cases, however, were the clinical Amsterdam criteria for diagnosing hereditary nonpolyposis colorectal cancer fulfilled. In the sebaceous tumors of the remaining six patients, high microsatellite instability was an incidental finding. In two of these six patients, single relatives were known to be affected with internal cancer; however, their family histories were not suggestive of Muir-Torre syndrome or hereditary nonpolyposis colorectal cancer. In comparison with microsatellite instability screening studies in a variety of other randomly selected tumors, our study identifies sebaceous gland neoplasias as tumors with the highest frequency of high microsatellite instability reported so far, whereas sebaceous gland hyperplasia rarely exhibits high microsatellite instability. Therefore, screening for microsatellite instability in sebaceous gland neoplasias will be of great value in the detection of an inherited DNA mismatch repair defect, which predisposes to various types of internal cancers.     

Multiple sebaceous gland hyperplasias in X chromosome hypohidrotic ectodermal dysplasia]

We report on a 46-year-old man with X-linked hypohidrotic ectodermal dysplasia, who presented with large skin areas covered with aggregated sebaceous gland papules on the face and neck. This is rare, but has been observed in very similar form in association with this disorder in a not insubstantial proportion of cases.     

Tandem BRAF mutations in primary invasive melanomas

The RAS/RAF/MAPK pathway likely mediates critical cell proliferation and survival signals in melanoma. BRAF mutations have been found in a high percentage of melanoma cell lines and metastases; however, only a few studies with a limited number of specimens have focused on primary melanomas. We examined BRAF exon 15 mutational status in 37 primary invasive melanomas of varying thicknesses, which had undergone a standardized pathology review. BRAF mutational status was determined using direct manual sequencing of PCR products, followed by resequencing separately amplified DNA aliquots to confirm each mutation. BRAF exon 15 mutations were found in 17 of 37 (46%) primary melanomas. Tumor-specific tandem mutations, encoding either V599K, V599R, or V599E, were found in 5 of 17 (29%) melanomas with BRAF exon 15 mutations. Cloning of BRAF double base-pair substitutions confirmed that both base changes were on the same allele and can result in a positive charge at codon 599. BRAF mutations, including tandem mutations, were frequently found in both thin and thick primary melanomas, implying that these mutations can occur early in the progression of melanoma. The finding of tandem mutations in thin melanomas makes it more likely that they arise as a simultaneous rather than sequential event.     

Activating BRAF mutations in eruptive melanocytic naevi

Background Eruptive melanocytic naevi (EMN) are melanocytic proliferations developing rapidly on previously unaffected skin in association with various clinical scenarios, most commonly systemic immunosuppression. However, the exact mechanism leading to development of EMN is not understood. In particular, it is not known whether EMN harbour the BRAF mutations which occur frequently in melanoma and most common naevi. Objectives To evaluate whether activating BRAF mutations may play a role in genesis of EMN. Methods Genomic DNA was isolated from 20 EMN from a patient treated with 6‐mercaptopurine (6‐MP). Primary BRAF genotyping was performed by allele‐specific polymerase chain reaction, followed by validation using direct sequencing. Results The BRAF V600E mutation was identified in 85% of EMN examined. Conclusions Our results implicate mutational activation of the BRAF–MAPK pathway as a factor in development of EMN in the setting of 6‐MP treatment. The mechanism leading to development of EMN in this, and potentially other patients, may relate to synergistic mutagenic effects of thioguanines and ultraviolet (UV) A. Together with the documented importance of BRAF mutations in melanoma development and maintenance, these findings highlight the importance of UVA protection, especially in patients treated with thiopurines such as 6‐MP.     

BRAF and KRAS mutations in sporadic glomus tumors

Glomus tumors are rare soft tissue neoplasms resembling the normal glomus body, which is a specialized form of arteriovenous anastomosis that regulates heat. The molecular genetics of sporadic glomus tumors has not been studied. We genotyped tumors from 28 patients (16 female patients and 12 male patients) ranging from 13 to 77 years and correlated the results with the tumor site (15 finger/1 hand/4 arm/7 leg/1 eyelid), Ki-67 index, and clinical follow-up. Tumor DNA from paraffin-embedded tissue was screened by multiplex polymerase chain reaction and mass spectroscopy, using a panel covering 370 mutations across 30 genes, including AKT1, BRAF, CTNNB1, EGFR, ERBB2, FGFR1/2/3, HRAS, KIT, KRAS, MEK1/2, NRAS, PDGFRA, and PIK3CA. A BRAF V600E mutation was identified in 3 cases, all of which occurred in proximal locations (upper shin, thigh, and upper arm). Two of the patients with BRAF-mutated tumors were quite young (21 and 13 years) and one of the BRAF-mutated tumors recurred in 3 years. A KRAS G12A mutation was found in tumor removed from the finger. Ki-67 index did not correlate with genotype. To our knowledge, this is the first report of oncogenic mutations in sporadic glomus tumors.     

新疆80例恶性黑素瘤BRAF基因突变分析

目的 探讨BRAF基因突变与恶性黑素瘤临床表现的关系。方法 PCR及DNA直接测序法对新疆80例恶性黑素瘤及30例正常皮肤石蜡包埋组织BRAF基因11、15外显子进行检测。结果 80例恶性黑素瘤19例发生BRAF基因突变,突变率为23.8%（19/80）;有17例突变发生于15外显子,突变率为89.5% （17/19）,其中V600E突变占BRAF基因15外显子突变的88.2% （15/17）;2例突变位于11外显子,突变率10.5%（2/19）;30例正常皮肤组织均未发现BRAF基因突变。患者平均发病年龄为57.5岁,年龄在60岁以下患者BRAF基因突变率显著高于60岁以上（χ2 = 6.613,P < 0.05）。黏膜、肢端、非肢端突变率分别为：18.2%（4/21）,14.7%（5/34）,41.7%（10/24）,差异具有统计学意义（χ2 = 6.167,P < 0.05）。BRAF基因突变与恶性黑素瘤患者性别、民族、有无淋巴结转移无明显相关性（P > 0.05）。结论 BRAF基因仍为新疆地区恶性黑素瘤热点突变基因,且以该基因15外显子V600E突变为主。BRAF基因突变与恶性黑素瘤患者发病年龄、发病部位密切相关,而与民族、性别、有无淋巴结转移无相关性。     

BRAF mutations are common somatic events in melanocytic nevi

We determined mutations in the BRAF, N-ras, and CDKN2A genes in 27 histologically diverse melanocytic nevi and corresponding surrounding tissues from 17 individuals. Mutations in the BRAF and N-ras gene were found in 22 nevi (81%) from 16 individuals (94%). The predominant BRAF mutation T1799A (V600E) was detected in 18 nevi; 1 nevus had a novel A1781G (D594V) mutation in the same gene and 3 nevi had mutations in codon 61 of the N-ras gene. In 4 individuals both nevi carried a BRAF mutation, whereas in 2 other individuals 1 nevus showed a BRAF mutation and the second nevus had an N-ras mutation. In 2 individuals normal skin distant from nevi showed a BRAF mutation. No mutations were detected in the CDKN2A gene. The mutations in the BRAF and N-ras genes, in this study, were not associated with histologic type, location, skin type, size, or numbers of nevi. Our results suggest that mutations in the BRAF gene and to some extent in the N-ras gene represent early somatic events that occur in melanocytic nevi. We hypothesize the dual effect of solar ultraviolet irradiation on melanoma, through mutagenesis and by increasing the number of melanocytic nevi, many of which carry a BRAF or N-ras mutation.     

Absence of BRAF and HRAS mutations in eruptive Spitz naevi

Background Eruptive Spitz naevi have been reported rarely in the literature. In solitary Spitz naevi, BRAF and HRAS mutations, as well as increased copy numbers of chromosome 11p have been identified. Objectives To investigate the genetic changes underlying eruptive Spitz naevi. Methods We report on a 16‐year‐old boy who developed multiple disseminated eruptive Spitz naevi within a few months. We analysed BRAF, HRAS, KRAS and NRAS genes in 39 naevi from this patient for hotspot mutations. Furthermore, comparative genomic hybridization analysis was performed in three lesions. Results None of the Spitz naevi displayed a mutation in the analysed genes, and no chromosomal imbalances were observed. Conclusions Our results indicate that the typical genetic alterations described in solitary Spitz naevi appear to be absent in eruptive Spitz naevi. Yet unknown alternative genetic alterations must account for this rare syndrome.     

BRAF mutations might be more common than supposed in vulvar melanomas

Data on BRAF, NRAS and KIT mutations are scarce in patients with vulvo‐vaginal melanomas and are associated with important therapeutic issues. We investigated their prevalence in a cohort of patients with female lower genital tract melanomas between 2003 and 2017. Of the 22 patients, 5 (22.7%) harboured a BRAF mutation, which was much higher than the rate of 5% reported in the literature. One patient, who was tested negative on the primary melanoma, had a NRAS mutation in a cutaneous metastasis. Our data provide a rationale for prospective and repeated mutations testing in female lower genital tract melanomas.     

BRAF point mutations in primary melanoma show different prevalences by subtype

To elucidate the biological significance of activating mutations of BRAF in human malignant tumors, we performed a mutation analysis using 43 cell lines established from tumors that had developed in several kinds of human organs. Because the same V599E point mutation was observed in three of six melanoma cell lines and no such mutations were observed in other types of cancers, we focused further on melanoma, performed mutation analyses of NRAS, KRAS, CTNNB1, and p16/p14(ARF) in these cell lines, and found one NRAS mutation and three p16/p14(ARF) mutations. We further searched for mutations of BRAF and NRAS in 35 primary sporadic melanomas from 35 Japanese patients and detected the V599E BRAF point mutation in only nine (26%) of them. Significant differences in mutation frequency were observed among four histological subtypes; four (50%) of eight superficially spreading melanoma and five (33%) of 15 acral lentiginous melanoma had the mutation, whereas none of 12 other types (six nodular melanoma, five lentigo melanoma, and one mucosal melanoma) had it. The BRAF mutation was observed frequently even in small lesions, indicating that activation of this gene may be one of the early events in the pathogenesis of some melanomas.     

MC1R variants increase risk of melanomas harboring BRAF mutations

Melanocortin-1 receptor (MC1R) variants have been associated with BRAF (v-raf murine sarcoma viral oncogene homolog B1) mutations in non-CSD (chronic solar-damaged) melanomas in an Italian and an American population. We studied an independent Italian population of 330 subjects (165 melanoma patients and 165 controls) to verify and estimate the magnitude of this association and to explore possible effect modifiers. We sequenced MC1R in all subjects and exon 15 of BRAF in 92/165 melanoma patients. Patients with MC1R variants had a high risk of carrying BRAF mutations in melanomas (odds ratio (OR)=7.0, 95% confidence interval (CI)=2.1-23.8) that increased with the number of MC1R variants and variants associated with red hair color. Combining these subjects with the originally reported Italian population (513 subjects overall), MC1R variant carriers had a 5- to 15-fold increased risk of BRAF-mutant melanomas based on carrying one or two variants (P<0.0001, test for trend), and regardless of signs of chronic solar damage. In contrast, no association with BRAF-negative melanomas was found (OR=1.0, 95% CI=0.6-1.6). No characteristics of subjects or melanomas, including age, nevus count, pigmentation, and melanoma thickness or location on chronically or intermittently sun-exposed body sites, substantially modified this association, although results could be affected by the small numbers in some categories. This study confirms that the known MC1R-melanoma risk association is confined to subjects whose melanomas harbor BRAF mutations.     

Beyond the BRAFV600E hotspot: biology and clinical implications of rare BRAF gene mutations in melanoma patients

BRAF gene mutations can be found in approximately 50% of melanomas, but the most common BRAF mutation leads to substitution at residue 600 of the protein, from valine to glutamic acid. BRAF^V600E occurs in up to 95% of all melanoma cases and can be successfully blocked by using a combination of BRAF‐ and MEK inhibitors. The wider availability of next‐generation sequencing is revealing more non‐V600 BRAF mutations, and the clinical implications of these mutations are widely unknown. In this review, we will discuss the biology of the MAPK pathway and the different types of BRAF mutations as well as their effect on MEK activation. Current literature will be reviewed including in vitro data, case reports and case series.     

遗传性对称性色素异常症两家系基因突变检测研究

目的:检测遗传性对称性色素异常症患者家系中腺苷脱氨酶(ADAR)基因的突变.方法:收集2个遗传性对称性色素异常症患者家系的临床资料,采用聚合酶链反应及直接测序法对家系内成员ADAR基因突变位点进行检测,同时对50名无血缘关系健康对照者的该位点进行直接测序.结果:在2个家系的患者中分别检测到2个不同的ADAR基因移码突变位点c.633insT和c.2742delC,而在家系内非患者及正常对照者中均未发现该2个突变.结论:该研究中2个遗传性对称性色素异常症家系中的患者存在ADAR基因的移码突变,且皆为首次报道.     

A case of multiple sebaceous epithelioma: analysis of microsatellite instability

Sebaceous gland tumor is a rare disease that is a sign of Muir-Torre syndrome, an autosomal, dominantly inherited genodermatosis characterized by the presence of at least one sebaceous gland tumor and a minimum of one internal malignancy. Recent studies have indicated that defective DNA mismatch repair occurs in Muir-Torre syndrome. Cutaneous lesions may occur before diagnosis of the internal cancer. We describe a 64-year-old male patient with multiple sebaceous epitheliomas with no evident internal malignancy. Microsatellite instability, determined by examining dinucleotide CA repeats at the microsatellite loci, was observed in DNA from one sebaceous epithelioma but not from the other two sebaceous epitheliomas or from one basal cell epithelioma with sebaceous differentiation, suggesting that this condition is unlikely to be due to germ-line mutation of mismatch repair genes.     

Examination of mutations in BRAF, NRAS, and PTEN in primary cutaneous melanoma

Frequent somatic mutation of v-raf murine sarcoma viral oncogene homolog B (BRAF), a downstream effector of the rat sarcoma oncogene (RAS) signaling pathway, is described in melanoma and other tumors. Our analysis of melanoma cell lines suggests that activating mutations in BRAF can occur simultaneously with inactivation of phosphatase and tensin homolog (PTEN), but neuroblastoma RAS (NRAS) mutations are not coincident. We determined the concurrent prevalence of mutations in BRAF and NRAS, and alteration of PTEN expression in 69 primary cutaneous melanomas. BRAF mutations were seen in 57% of cases. NRAS was mutated in 17% of samples, exclusively in exon 2. Two cases showed concurrent BRAF and NRAS mutations. Using immunohistochemistry, PTEN protein expression was lost or greatly reduced in 19% of tumors. Seven tumors with reduced PTEN yielded DNA amenable to sequencing, and three also showed mutation in BRAF but none in NRAS. In all, 11 (85%) of 13 tumors showing reduced PTEN expression were greater than 3.5 mm thick, and the association of increasing Breslow thickness and loss or reduction of PTEN expression was statistically significant (P<0.0001). Mutations in NRAS were not coincident with reduced PTEN expression, and the concurrent mutation of NRAS and BRAF was rare.