Abdominal inflammatory myofibroblastic tumour: Clinicopathological and molecular analysis of 20 cases, highlighting potential therapeutic targets.

AIMS: Inflammatory myofibroblastic tumour (IMT) is a rare mesenchymal neoplasm of intermediate malignant potential, occurring at any age and at multiple sites. Epithelioid inflammatory myofibroblastic sarcoma (EIMS) is an aggressive subtype of IMT, typically involving the abdomen. Most IMTs harbour kinase gene fusions, especially involving ALK and ROS1, but 20-30% of IMTs show no detectable translocations. The aim of this study is to further delineate clinicopathological and molecular characteristics of abdominal IMT and discover potential new therapeutic targets. METHODS AND RESULTS: In 20 IMTs, including four EIMS, RNA fusion analysis was performed, followed by multiplex DNA analysis if no ALK or ROS1 fusion was detected. Fourteen IMTs (70.0%) had an ALK translocation and the fusion partner was identified in 11, including a RRBP1::ALK fusion, not previously described in classical (non-EIMS) IMT. RANBP2::ALK fusion was demonstrated in all EIMS. One IMT had a ROS1 fusion. In all ALK/ROS1 translocation-negative IMTs mutations or fusions - as yet unreported in primary IMT - were found in genes related to the receptor tyrosine kinase (RTK)/PI3K/AKT pathway. Three of four patients with EIMS died of disease [mean survival 8 months (4-15 months)], whereas only one of 14 classical IMT patients succumbed to disease [mean follow-up time 52 months (2-204 months); P < 0.01]. CONCLUSION: This study shows the wide clinical spectrum of abdominal IMTs and affirms the poor prognosis of EIMS, raising discussion about its status as IMT subtype. Furthermore, the newly detected alterations of the RTK/PI3K/AKT pathway expand the molecular landscape of IMTs and provide potential therapeutic targets.

Mapping of Human Polyomavirus in Renal Cell Carcinoma Tissues.

Worldwide, the incidence of renal cell carcinoma (RCC) is rising, accounting for approximately 2% of all cancer diagnoses and deaths. The etiology of RCC is still obscure. Here, we assessed the presence of HPyVs in paraffin-embedded tissue (FFPE) resected tissue from patients with RCC by using different molecular techniques. Fifty-five FFPE tissues from 11 RCC patients were included in this study. Consensus and HPyV-specific primers were used to screen for HPyVs. Both PCR approaches revealed that HPyV is frequently detected in the tissues of RCC kidney resections. A total of 78% (43/55) of the tissues tested were positive for at least one HPyV (i.e., MCPyV, HPyV6, HPyV7, BKPyV, JCPyV, or WUyV). Additionally, 25 tissues (45%) were positive for only one HPyV, 14 (25%) for two HPyVs, 3 (5%) for three HPyVs, and 1 one (1%) tissue specimen was positive for four HPyVs. Eleven (20%) RCC specimens were completely devoid of HPyV sequences. MCPyV was found in 24/55 RCC tissues, HPyV7 in 19, and HPyV6 in 8. The presence of MCPyV and HPyV6 was confirmed by specific FISH or RNA-ISH. In addition, we aimed to confirm HPyV gene expression by IHC. Our results strongly indicate that these HPyVs infect RCC and nontumor tissues, possibly indicating that kidney tissues serve as a reservoir for HPyV latency. Whether HPyVs possibly contribute to the etiopathogenesis of RCC remains to be elucidated.

Optical coherence tomography versus punch biopsy for diagnosis of basal cell carcinoma: a multicentre, randomised, non-inferiority trial.

BACKGROUND: Punch biopsy is the gold standard for diagnosis and subtyping of basal cell carcinoma. The aim of this study was to assess whether use of optical coherence tomography (OCT), a non-invasive imaging tool, might avoid the need for biopsy. METHODS: In a multicentre, randomised, non-inferiority trial, patients (aged ≥18 years) with an indication for biopsy of a suspected basal cell carcinoma outside the H-zone (high-risk zone) of the face were randomly assigned (1:1) to receive either OCT or punch biopsy (regular care) via a web-based randomisation system. Patients were enrolled from three participating centres in the Netherlands: Maastricht University Medical Centre+, Catharina Hospital Eindhoven, and Zuyderland Medical Centre Heerlen. Stratification factors for randomisation were participating centre and the grade of clinical basal cell carcinoma suspicion (high vs low). The primary endpoint was the proportion of patients free from a recurrent or residual lesion (malignant or premalignant) 12 months after treatment. Modified intention-to-treat and per-protocol analyses were conducted, with a predefined non-inferiority margin of -10%. This trial is registered with ClinicalTrials.gov number, NCT03848078, and is complete. FINDINGS: Between Feb 25, 2019, and Sept 2, 2020, 598 patients were enrolled and randomly assigned to either the regular care group (n=299) or the OCT group (n=299). Data on the primary endpoint were available in 553 patients (n=268 in the regular care group, n=285 in the OCT group). After median follow-up of 12·7 months (IQR 11·2-14·1) in the OCT group and 12·6 months (10·8-14·3) in the regular care group, 253 (94%) of 268 patients in the OCT group and 266 (93%) of 285 patients in the regular care group were free from recurrent or residual lesions (malignant or pre-malignant) 12 months after treatment. According to our modified intention-to-treat analysis, the absolute difference (OCT vs regular care) was 1·07% (95% CI -2·93 to 5·06; one-sided p=0·30), with the lower limit of the 95% CI not exceeding the predefined non-inferiority margin of -10%. Per-protocol analyses led to proportions free from a residual or recurrent lesion (premalignant or malignant) of 95% (250 of 263) in the OCT group and 94% (262 of 278) in the regular care group, and an absolute difference of 0·81% (95% CI -2·98 to 4·60; one-sided p=0·34). INTERPRETATION: OCT-guided diagnosis and treatment of basal cell carcinoma is non-inferior to regular care punch biopsy. Implementation of OCT for diagnosis of basal cell carcinoma could reduce the number of consultations and invasive procedures. FUNDING: The Netherlands Organization for Health Research and Development and Maurits en Anna de Kock Stichting.

Rethinking the biology of metastatic melanoma: a holistic approach.

Over the past decades, melanoma-related mortality has remained nearly stable. The main reason is treatment failure of metastatic disease and the inherently linked knowledge gap regarding metastasis formation. In order to elicit invasion, melanoma cells manipulate the tumor microenvironment, gain motility, and adhere to the extracellular matrix and cancer-associated fibroblasts. Melanoma cells thereby express different cell adhesion molecules like laminins, integrins, N-cadherin, and others. Epithelial-mesenchymal transition (EMT) is physiological during embryologic development, but reactivated during malignancy. Despite not being truly epithelial, neural crest-derived malignancies like melanoma share similar biological programs that enable tumorigenesis, invasion, and metastasis. This complex phenomenon is termed phenotype switching and is intertwined with oncometabolism as well as dormancy escape. Additionally, it has been shown that primary melanoma shed exosomes that create a favorable premetastatic niche in the microenvironment of secondary organs and lymph nodes. Although the growing body of literature describes the aforementioned concepts separately, an integrative holistic approach is missing. Using melanoma as a tumor model, this review will shed light on these complex biological principles in an attempt to clarify the mechanistic metastatic pathways that dictate tumor and patient fate.

Cutaneous metastases of internal malignancies: a single-institution experience.

AIMS: Cutaneous metastases of internal malignancies occur in 1-10% of cancer patients. The diagnosis can sometimes be challenging, especially in cases with an unknown primary cancer. MATERIALS AND METHODS: A retrospective case review was performed including all cases of skin metastases from primary internal malignancies diagnosed at the Department of Pathology at the Maastricht University Medical Centre+ from 2007 to 2021. The clinicopathological data were collected and immunohistochemical and molecular diagnostic tests were performed to confirm the primary origin of the metastases. RESULTS: We identified 152 cases (71 female; 31 male patients) of cutaneous metastases of internal malignancies. 28 patients (20 women and 8 men) were diagnosed with multiple cutaneous metastases. Among the female patients, the most common primary tumour was breast cancer (50% of the cases), followed by lung (13.6%), gynaecological (7.3%), and gastrointestinal origin (7.3%). Among the male patients, the most common primary sites were gastrointestinal and lung origin (altogether, 50% of the cases). In 19 patients, the cutaneous metastasis was the first presentation of a clinically silent internal malignancy (18.6%), of which most (78.9%) represented metastatic lung carcinomas. Finally, metastasizing patterns were different across tumour types and gender. CONCLUSION: Breast, lung, gastrointestinal, and gynaecologic cancers are the most common primary tumours demonstrating skin metastases. Infrequently, cutaneous metastases can be the first clinically visual manifestation of an underlying not yet diagnosed internal malignancy; therefore, occasional broad immunohistochemical profiling, molecular clonal analysis, and a continuous high level of awareness are necessary for a precise diagnosis of cutaneous metastases of internal malignancies.

Integrative histopathological and immunophenotypical characterisation of the inflammatory microenvironment in spitzoid melanocytic neoplasms.

AIMS: The role of inflammation in conventional cutaneous melanoma has been extensively studied, whereas only little is known about the inflammatory microenvironment and immunogenic properties of spitzoid melanocytic neoplasms. The composition of infiltrating immune cells and the architectural distribution of the inflammation, in particular, are still obscure. This is the first study, to our knowledge, to systematically characterise the inflammatory patterns and the leucocyte subsets in spitzoid melanocytic lesions. METHODS AND RESULTS: We examined 79 spitzoid neoplasms including banal Spitz naevi (SN, n = 50), atypical Spitz tumours (AST, n = 17) and malignant Spitz tumours (MST, n = 12) using histopathological analysis and immunohistochemistry. Spitzoid melanocytic lesions showed a high frequency (67.1%, n = 53 of 79) of inflammation. Four inflammatory patterns were identified according to architectural composition, distribution and intensity of inflammation. The majority of the inflammatory infiltrate corresponded to CD3+ /CD8+ T lymphocytes (56.1%), followed by CD3+ /CD4+ T cells (35.7%) and CD68+ histiocytes (20.3%). CD3+ /TIA-1+ cytotoxic T lymphocytes constituted 3.7% of inflammatory cells. Rarely, CD3+ / granzyme B+ cytotoxic T lymphocytes (2.7%) and CD138+ plasma cells (0.5%) were detected in the infiltrating immune cells. There was no significant difference in the inflammatory cellular composition among the spitzoid melanocytic subgroups (SN versus AST versus MST). CONCLUSION: Our findings demonstrate that Spitz tumours are highly immunogenic lesions. Inflammation with the presence of lymphocytic aggregates predominated in SN, but was not distinctive for this melanocytic category. A strong and intense inflammation was suggestive of an underlying malignancy. The infiltrating cytotoxic T lymphocyte subsets in Spitz tumours deserve further investigation in larger study cohorts to elucidate prognostic and immuno-oncological therapeutic relevance.

Molecular testing in metastatic basal cell carcinoma.

BACKGROUND: Metastatic basal cell carcinoma (mBCC) is a very rare entity, and diagnosis can be challenging. Therapeutic options are limited, and response to targeted therapy is poor. OBJECTIVE: To demonstrate a clonal relationship between BCCs and their metastases and to explore which hedgehog pathway-related mutations are involved in mBCC. METHODS: Genetic analysis was conducted in 10 primary BCCs and their metastases. Genes relevant for BCC development were analyzed in tumor and metastasis material with small molecule molecular inversion probes (smMIPs) for PTCH1, PTCH2, SMO, SUFU, GLI2, and TP53 or with targeted next generation sequencing of the same genes and CDKN2A, CDKN2B, CIC, DAXX, DDX3X, FUBP1, NF1, NF2, PTEN, SETD2, TRAF7, and the TERT promoter. RESULTS: In 8 of 10 patients, identical gene mutations could be demonstrated in the primary tumors and their metastases. A broad spectrum of mutations was found. Four patients had SMO mutations in their tumor or metastasis, or both. All SMO mutations found were known to cause resistance to targeted therapy with vismodegib. LIMITATIONS: In 2 patients there was insufficient qualitative DNA available for genetic analysis. CONCLUSIONS: Molecular testing can help to identify the origin of a BCC metastasis and may be of prognostic and therapeutic value.

Surgery versus combined treatment with curettage and imiquimod for nodular basal cell carcinoma: One-year results of a noninferiority, randomized, controlled trial.

PURPOSE: Nodular basal cell carcinoma (nBCC) is mostly treated with surgical excision. Interest in minimally invasive treatment of these low-risk tumors is increasing. We assessed the effectiveness of nBCC treatment with curettage and imiquimod cream compared with surgical excision. METHODS: Patients with nBCC included in this randomized, controlled noninferiority trial were randomly assigned to either a curettage and imiquimod cream group or a surgical excision group. The primary endpoint was the proportion of patients free from treatment failure 1 year after the end of treatment. A prespecified noninferiority margin of 8% was used. A modified intention-to-treat and a per-protocol analysis was performed (ClinicalTrials.gov identifier NCT02242929). RESULTS: One hundred forty-five patients were randomized: 73 to the curettage and imiquimod cream group and 72 to the surgical excision group. The proportion of patients free of recurrence after 12 months was 86.3% (63/73) for the curettage and imiquimod group and 100% (72/72) for the surgical excision group. The difference in efficacy was -13.7% (95% confidence interval -21.6% to -5.8%; 1-sided P = .0004) favoring surgical excision. CONCLUSION: Noninferiority of curettage and imiquimod cream cannot be concluded. Given the still high efficacy of curettage and imiquimod cream and the indolent growth pattern of nBCC, curettage and imiquimod could still be a valuable treatment option with the possibility to prevent overuse of excisions. However, it cannot replace surgical excision.

Trends in the Incidence of Bowen Disease Based on a Single-Center Study in the Netherlands.

BACKGROUND: Incidence trends of nonmelanoma skin cancer show an increase. Few data have been published about the incidence of Bowen disease (BD). Three previous studies, conducted more than 15 years ago in North America, found large variation in incidence rates in Caucasians, and trends over longer periods have never been studied. OBJECTIVE: To estimate the incidence of BD in a Caucasian population in Northern Europe (Maastricht, the Netherlands) between 2003 and 2013. METHODS: Primary and histologically confirmed BD, diagnosed in Maastricht, the Netherlands, in the years 2003, 2008, and 2013, was retrieved from a pathology database. Age-standardized and sex-specific incidence rates per 100,000 inhabitants were calculated by using the age distribution of the European standard population of 2013. RESULTS: A statistically significant increase in the annual age-standardized incidence rates per 100,000 people was found from 8.1 (95% confidence interval [CI] 3.7-12.5) in 2003 to 68.9 (95% CI 57.2-80.7) in 2013 (p < .001). For women, there was an increase from 7.7/100,000 (95% CI 2.0-13.4) in 2003 to 76.8/100,000 (95% CI 60.2-93.5) in 2013, respectively (p < .001). An increase from 8.8/100,000 (95% CI 1.8-15.9) in 2003 to 59.2/100,000 men (95% CI 42.8-75.6) in 2013 (p < .001) was found. CONCLUSION: These findings suggest an increase in the annual age-standardized incidence rates in BD.

The effect of topical diclofenac 3% and calcitriol 3 µg/g on superficial basal cell carcinoma (sBCC) and nodular basal cell carcinoma (nBCC): A phase II, randomized controlled trial.

BACKGROUND: Nonsteroidal anti-inflammatory drugs and vitamin-D derivatives can target signaling pathways activated in basal cell carcinoma (BCC). OBJECTIVE: We investigated the efficacy of topically applied diclofenac sodium 3% gel, calcitriol 3 µg/g ointment, and a combination of both in superficial BCC (sBCC) and nodular BCC. METHODS: Patients with a primary, histologically proven sBCC (n = 64) or nodular BCC (n = 64) were randomized to topical diclofenac, calcitriol, combination of both, or no topical treatment (control group). After self-application twice daily under occlusion (8 weeks), tumors were excised. Primary outcome was posttreatment expression levels of proliferation (Ki-67) and antiapoptosis (B-cell lymphoma [Bcl-2]) immunohistochemical markers. Secondary outcomes were histologic clearance, adverse events, application-site reactions, and patient compliance. RESULTS: sBCC treated with diclofenac showed a significant decrease in Ki-67 (P < .001) and Bcl-2 (P = .001), and after combination therapy for Ki-67 (P = .012). Complete histologic tumor regression was seen in 64.3% (P = .0003) of sBCC (diclofenac) and 43.8% (P = .007) of sBCC (combination therapy) compared with 0.0% of controls. No significant changes were found in nodular BCC. Application-site reactions were mostly mild to moderate. LIMITATIONS: The sample size was small. CONCLUSION: Our results suggest that topical diclofenac is a promising new treatment for sBCC. Its mode of action differs from available noninvasive therapies, and thus has an additive value.

Biallelic inactivation of protoporphyrinogen oxidase and hydroxymethylbilane synthase is associated with liver cancer in acute porphyrias.

Variegate porphyria (VP) and acute intermittent porphyria (AIP), the two most common types of acute porphyrias (AHPs), result from a partial deficiency of protoporphyrinogen oxidase (PPOX) and hydroxymethylbilane synthase (HMBS), respectively. A rare but serious complication in the AHPs is hepatocellular carcinoma (HCC). However, the underlying pathomechanisms are yet unknown. We performed DNA sequence analysis in cancerous and non-cancerous liver tissue of a VP and an AIP patient, both with HCC. In samples of both cancerous and non-cancerous liver tissues from the patients, we identified the underlying PPOX and HMBS germline mutations, c.1082dupC and p.G111R, respectively. Additionally, we detected a second somatic mutation, only in the cancer tissue i.e., p.L416X in the PPOX gene of the VP patient and p.L220X in the HMBS gene of the AIP patient, both located in trans to the respective germline mutations. Both somatic mutations were not detected in 10 non-porphyria-associated HCCs. Our data demonstrate that in the hepatic cancer tissue of AHP patients, somatic second-hit mutations result in nearly complete inactivation of the enzymes catalyzing major steps in the heme biosynthetic pathway. Both PPOX and HMBS, which might act as tumor suppressors, play a crucial role in the development of HCC in these individuals.

Familial pityriasis rubra pilaris is caused by mutations in CARD14.

Pityriasis rubra pilaris (PRP) is a papulosquamous disorder phenotypically related to psoriasis. The disease has been occasionally shown to be inherited in an autosomal-dominant fashion. To identify the genetic cause of familial PRP, we ascertained four unrelated families affected by autosomal-dominant PRP. We initially mapped PRP to 17q25.3, a region overlapping with psoriasis susceptibility locus 2 (PSORS2 [MIM 602723]). Using a combination of linkage analysis followed by targeted whole-exome sequencing and candidate-gene screening, we identified three different heterozygous mutations in CARD14, which encodes caspase recruitment domain family, member 14. CARD14 was found to be specifically expressed in the skin. CARD14 is a known activator of nuclear factor kappa B signaling, which has been implicated in inflammatory disorders. Accordingly, CARD14 levels were increased, and p65 was found to be activated in the skin of PRP-affected individuals. The present data demonstrate that autosomal-dominant PRP is allelic to familial psoriasis, which was recently shown to also be caused by mutations in CARD14.

Tumor thickness and adnexal extension of superficial basal cell carcinoma (sBCC) as determinants of treatment failure for methylaminolevulinate (MAL)-photodynamic therapy (PDT), imiquimod, and 5-fluorouracil (FU).

BACKGROUND: Noninvasive treatments are frequently used in treatment of superficial basal cell carcinoma (sBCC) because of better cosmetic results, lower costs, and less burden on health care services when compared with surgical excision. However, probability of treatment failure is higher after noninvasive therapies and may depend on histologic tumor characteristics. OBJECTIVE: We sought to investigate whether tumor thickness and adnexal extension are determinants of treatment failure in sBCC treated with topical methylaminolevulinate-photodynamic therapy, imiquimod, or 5-fluorouracil. METHODS: Data were derived from a randomized controlled trial on the effectiveness of methylaminolevulinate photodynamic therapy, imiquimod, and 5-fluorouracil for treatment of sBCC (ISRCTN79701845). For tumors with treatment failure (n = 112) and a randomly selected control group of tumors without treatment failure (n = 224) data on tumor thickness and adnexal extension were retrospectively collected. Treatment failure was defined as a clinically and histologically persistent or recurrent tumor within 1-year posttreatment. RESULTS: Tumor thickness of included patients ranged from 0.2 to 1.0 mm. Tumor thickness and adnexal extension of sBCC were not significantly associated with treatment failure of methylaminolevulinate photodynamic therapy, imiquimod, or 5-fluorouracil. LIMITATIONS: Follow-up period of 1 year is a limitation. CONCLUSION: There seems to be no need to determine tumor thickness or adnexal extension in sBCC before treatment.

Photodynamic therapy in Bowen's disease: influence of histological features and clinical characteristics on its success.

BACKGROUND: In Bowen's disease (BD) there is no consensus on optimal treatment. Photodynamic therapy (PDT) is an effective non-invasive treatment modality for BD with excellent cosmetic results. OBJECTIVE: This retrospective study examines whether clinical and histological features of BD impact PDT response. METHODS: Patients with previously untreated BD from 2002 until 2007 were identified at the Maastricht University Medical Centre. Patients treated with PDT were included. All histological slides were re-examined. RESULTS: During the study period 98 tumours were treated with PDT. In univariate analysis severe atypia and higher age were associated with decreased probability of clinical clearance. Higher age was also associated with an increased risk of recurrence. In multivariate analysis severe atypia remained the only independent risk factor for therapy failure. CONCLUSION: In patients with BD, severe atypia and higher age are associated with an increased risk of treatment failure after PDT.

Bowen's disease: A six-year retrospective study of treatment with emphasis on resection margins.

Bowen's disease is an in situ squamous cell carcinoma of the skin with various treatment modalities available. A major advantage of surgical excision is the opportunity to histologically examine the resection margins. There is no consensus about the most appropriate margin. This retrospective study evaluates the clearance rates achieved by excision with a 5 mm margin and estimates how that might change after fictitiously reducing the resection margin by 1 or 2 mm. Patients with histologically confirmed Bowen's disease were selected at the Maastricht University Medical Centre from 2002 until 2007. Surgical margins and complete excision rates were evaluated and histological slides were re-examined. To our knowledge this is the first study investigating the safety margin for Bowen's disease. As Bowen's disease is not an invasive disease, minimisation of healthy tissue excision is desirable. Our data show that a hypothetical reduction of the safety margin from 5 mm to 4 or 3 mm decreases the complete excision rate from 94.4% to 87% and 74.1%, respectively.

Bovine Meat and Milk Factor-like Sequences Are Frequently Detected in Renal Cell Carcinoma Tissues.

Previous studies have indicated a potential role of diet in the pathogenesis of renal cell carcinoma (RCC). Recently, circular bovine meat and milk factor (BMMF) DNAs have been identified in peritumoral tissues of human colon and breast cancers. Here, we investigated the prevalence of the DNA of these novel human pathogenic infectious agents in RCC and adjacent peritumoral renal tissues. DNA was extracted from formalin-fixed and paraffin-embedded (FFPE) RCC and peritumoral kidney tissues, including a test (n = 11) and a validation (n = 152) collection. BMMF1 and BMMF2 consensus primers were designed to screen for the presence of BMMF1- and BMMF2-like DNA. In addition, BMMF-specific PCR was performed on selected cases to test for the presence of additional regions of BMMF1 and BMMF2 genomes. A reference collection of hepatocellular carcinomas (HCCs; n = 60) and adjacent peritumoral liver tissues (n = 50) was also included. Our results demonstrated that BMMF1 and BMMF2 DNAs are frequently found in human RCC tissues and are particularly more prevalent in peritumoral kidney tissues. Of note, BMMF1 and BMMF2 genotype heterogeneity was higher in peritumoral kidney tissues compared to RCC tissues. This is the first study to directly test human FFPE tissues for BMMF1- and BMMF2-like DNA using consensus PCR and demonstrate BMMF DNA in neoplastic and peritumoral kidney tissues. The findings are in line with the recently proposed indirect etiopathogenetic role of BMMFs in, e.g., colorectal carcinogenesis. Follow-up studies are needed to explore the potential role of BMMFs in the etiopathogenesis of RCC.

Genetics and epigenetics of cutaneous malignant melanoma: a concert out of tune.

Cutaneous malignant melanoma (CMM) is the most life-threatening neoplasm of the skin and is considered a major health problem as both incidence and mortality rates continue to rise. Once CMM has metastasized it becomes therapy-resistant and is an inevitably deadly disease. Understanding the molecular mechanisms that are involved in the initiation and progression of CMM is crucial for overcoming the commonly observed drug resistance as well as developing novel targeted treatment strategies. This molecular knowledge may further lead to the identification of clinically relevant biomarkers for early CMM detection, risk stratification, or prediction of response to therapy, altogether improving the clinical management of this disease. In this review we summarize the currently identified genetic and epigenetic alterations in CMM development. Although the genetic components underlying CMM are clearly emerging, a complete picture of the epigenetic alterations on DNA (DNA methylation), RNA (non-coding RNAs), and protein level (histone modifications, Polycomb group proteins, and chromatin remodeling) and the combinatorial interactions between these events is lacking. More detailed knowledge, however, is accumulating for genetic and epigenetic interactions in the aberrant regulation of the INK4b-ARF-INK4a and microphthalmia-associated transcription factor (MITF) loci. Importantly, we point out that it is this interplay of genetics and epigenetics that effectively leads to distorted gene expression patterns in CMM.