Rockville Merkel Cell Carcinoma Group. Merkel cell carcinoma: recent progress and current priorities on etiology, pathogenesis, and clinical management

War or peace: Viruses and metastasis

Metastasis, the dissemination of malignant cells from a primary tumor to secondary sites, poses a catastrophic burden to cancer treatment and is the predominant cause of mortality in cancer patients. Metastasis as one of the main aspects of cancer progression could be strongly under the influence of viral infections. In fact, viruses have been central to modern cancer research and are associated with a great number of cancer cases. Viral-encoded elements are involved in modulating essential pathways or specific targets that are implicated in different stages of metastasis. Considering the continuous emergence of new viruses and the establishment of their contribution to cancer progression, the warfare between viruses and cancer appears to be endless. Here we aimed to review the critical mechanism and pathways involved in cancer metastasis and the influence of viral machinery and various routes that viruses adopt to manipulate those pathways for their benefit.

Merkel Cell Carcinoma Metastases to Caruncle With Orbital Extension: Report and Literature Review

Merkel cell carcinoma (MCC) is an uncommon and aggressive skin cancer of neuroendocrine origin. The tumor usually presents with a locoregional spread and most frequently metastasizes to the skin, liver, bone, lung, and brain. Despite the orbit being a relatively common site of metastases, it has rarely been reported in patients with MCC. The authors present a case of biopsy-proven orbital metastatic MCC in an 86-year-old male who presented with a rapidly enlarging right caruncle/subconjunctival mass with orbital extension and a history of forearm MCC excision 3 years prior. There are only 3 reported cases of distant metastatic MCC to the orbit, all presenting as a mass originating from extraocular muscles; and no cases of caruncle involvement.

Postoperative Radiation Therapy Is Indicated for "Low-Risk" Pathologic Stage I Merkel Cell Carcinoma of the Head and Neck Region but Not for Other Locations

Purpose

The role of postoperative radiation therapy (PORT) in early stage Merkel cell carcinoma (MCC) is controversial. We analyzed the role of PORT in preventing local recurrences (LR) among patients with low-risk, pathologic stage I MCC based on the location of the primary tumors: head/neck (HN) versus non-HN sites.

Methods and Materials

One hundred forty-seven patients with MCC were identified that had "low risk" disease (pathologic T1 primary tumor, negative microscopic margins, negative pathologic node status, no immunosuppression or prior systemic therapy). LR was defined as tumor recurrence within 2 cm of the primary surgical bed, and its frequency was estimated with the cumulative incidence method.

Results

Seventy-nine patients received PORT (30 HN, 49 non-HN) with a median dose of 50 Gy (range, 8-64 Gy) and 68 patients were treated with surgery alone (30 HN, 38 non-HN). Overall, PORT was associated with a decreased risk of LR (5-year rate: 0% vs 9.5%; P = .004) with 6 LRs observed in the surgery alone group. Although the addition of PORT significantly reduced LR rates among patients with HN MCC (0% vs. 21%; P = .034), no LRs were observed in patients with non-HN MCC managed with surgery alone. There was no significant difference in MCC-specific survival comparing HN versus non-HN groups, with or without PORT.

Conclusions

For low-risk, pathologic stage I MCC of the extremities and trunk, excellent local control rates were achieved with surgery, and PORT is not indicated. However, PORT was associated with a significant reduction in LRs among low-risk MCC of the HN.

Comparison of Prognostic Factors for Merkel Cell Carcinoma, Mucosal Melanoma and Cutaneous Malignant Melanoma: Insights into Their Etiologies

Little is known about the epidemiology of Merkel cell carcinoma (MCC) and mucosal melanoma (MM). Using the United States (US) National Cancer Institute’s Surveillance, Epidemiology, and End Results (SEER) program data, we compared MCC and MM with cutaneous malignant melanoma (CMM) with respect to incidence rates and prognostic factors to better understand disease etiologies. We describe the proportional incidences of the three cancers along with their survival rates based on 20 years of national data. The incidence rates in 2000–2019 were 203.7 per 1,000,000 people for CMM, 5.9 per 1,000,000 people for MCC and 0.1 per 1,000,000 people for MM. The rates of these cancers increased over time, with the rate of MM tripling between 2000–2009 and 2010–2019. The incidences of these cancers increased with age and rates were highest among non-Hispanic Whites. Fewer MCCs and MMS were diagnosed at the local stage compared with CMM. The cases in the 22 SEER registries in California were not proportional to the 2020 population census but instead were higher than expected for CMM and MCC and lower than expected for MM. Conversely, MM rates were higher than expected in Texas and New York. These analyses highlight similarities in the incidence rates of CMM and MCC—and differences between them and MM rates—by state. Understanding more about MCC and MM is important because of their higher potential for late diagnosis and metastasis, which lead to poor survival.

Prevalence of Merkel Cell Polyomavirus in Normal and Lesional Skin: A Systematic Review and Meta-Analysis

The prevalence of Merkel cell polyomavirus(MCPyV) in Merkel cell carcinoma(MCC) and non-MCC skin lesions and its possible role in the etiology of other skin diseases remain controversial. To systematically assess the association between MCPyV infection and MCC, non-MCC skin lesions, and normal skin. For this systematic review and meta-analysis, a comprehensive search for eligible studies was conducted using Medline Ovid, Pubmed, Web of Science, and the Cochrane CENTRAL databases until August 2021; references were searched to identify additional studies. Observational studies that investigated the association between MCPyV infection and MCC, non-MCC skin lesions, and normal skin using polymerase chain reaction(PCR) as a detection method and provided sufficient data to calculate the prevalence of MCPyV positivity. A total of 50 articles were included in the study after exclusion criteria were applied. Two reviewers independently reviewed and assessed the eligibility of the studies, and all disagreements were resolved by consensus. To determine the association between MCPyV and MCC, overall odds ratio (OR) were calculated with 95% CI using a random-effects model. Single-arm meta-analyses were performed to examine the prevalence rate of MCPyV+ in MCC, non-MCC skin lesions, and normal skin. The primary analysis was the prevalence rate of MCPyV+ in MCC. Secondary outcomes included the prevalence rate of MCPyV+ in non-MCC skin lesions and normal skin. A total of 50 studies involving 5428 patients were reviewed based on our inclusion and exclusion criteria. Compared with the control group, MCPyV infection was significantly associated with MCC (OR = 3.51, 95% CI = 2.96 - 4.05). The global prevalence of MCPyV+ in MCC, melanoma, squamous cell carcinoma, basal cell carcinoma, Bowen's disease, actinic keratosis, keratoacanthoma, seborrheic keratosis, and normal skin was 80%, 4%, 15%, 15%, 21%, 6%, 20%, 10%, and 11%, respectively. The current results suggest that MCPyV infection is significantly associated with an increased risk of MCC. However, the low prevalence rate of MCPyV+ in non-MCC skin lesions does not exclude a pathogenic association of this virus with the development of non-MCC skin lesions.

Merkel Cell Polyomavirus Small Tumor Antigen Activates Matrix Metallopeptidase-9 Gene Expression for Cell Migration and Invasion

Merkel cell polyomavirus (MCV) small T antigen (sT) is the main oncoprotein for the development of Merkel cell carcinoma (MCC). MCC is a rare, clinically aggressive neuroendocrine tumor of the skin with a high propensity for local, regional, and distant spread. The dysregulation of matrix metalloproteinase-9 (MMP-9) has been implicated in multiple essential roles in the development of various malignant tumor cell invasion and metastasis. Previously, MCV sT was shown to induce the migratory and invasive phenotype of MCC cells through the transcriptional activation of the sheddase molecule, ADAM 10 (A disintegrin and metalloprotease domain-containing protein 10). In this study, we show that MCV sT protein stimulates differential expression of epithelial-mesenchymal transition (EMT)-associated genes, including MMP-9 and Snail. This effect is dependent on the presence of the large T stabilization domain (LSD), which is known to be responsible for cell transformation through targeting of promiscuous E3 ligases, including FBW7, a known MMP-9 and Snail regulator. Chemical treatments of MMP-9 markedly inhibited MCV sT-induced cell migration and invasion. These results suggest that MCV sT contributes to the activation of MMP-9 as a result of FBW7 targeting and increases the invasive potential of cells, which can be used for targeted therapeutic intervention.IMPORTANCE Merkel cell carcinoma (MCC) is the most aggressive cutaneous tumor without clearly defined treatment. Although MCC has a high propensity for metastasis, little is known about the underlying mechanisms that drive MCC invasion and metastatic progression. MMP-9 has been shown to play a detrimental role in many metastatic human cancers, including melanoma and other nonmelanoma skin cancers. Our study shows that MCV sT-mediated MMP-9 activation is driven through the LSD, a known E3 ligase-targeting domain, in MCC. MMP-9 may serve as the biochemical culprit to target and develop a novel approach for the treatment of metastatic MCC.

Prognostic Impact of MCPyV and TIL Subtyping in Merkel Cell Carcinoma: Evidence from a Large European Cohort of 95 Patients

Merkel cell carcinoma is a rare (∼ 2000 cases/year in the USA) but aggressive neuroendocrine neoplasm of the skin. In 2008, the Merkel cell polyomavirus (MCPyV) was found to be clonally integrated in approximately 80% of Merkel cell carcinomas. The remaining 20% have large numbers of UV-associated mutations. Importantly, both the UV-induced neoantigens in virus-negative Merkel cell carcinoma and the Merkel cell polyomavirus oncogenes that are required for virus-positive tumor growth are highly immunogenic. Indeed, antigen-specific T cells detected in patients are frequently "dysfunctional/exhausted," and the inhibitory ligand PD-L1 is often expressed by Merkel cell carcinoma cells. These data led to point our attention on the quantity and the quality of the immune response in Merkel cell carcinoma. Here, we found CD8+ lymphocytes are the only singly evaluated lymphocyte subclass that strongly influenced overall survival and disease-specific survival in Merkel cell carcinoma. In addition, we highlighted as Merkel cell polyomavirus is a strong prognostic factor and as it prompts a host immune response involving various lymphocyte subclasses (CD3, CD8, FoxP3, and PD-L1 positive) in MCC. For this reason, we proposed a novel eye-based "immunoscore" model, obtained by tumor infiltrating lymphocytes subtyping (CD3, CD8, FoxP3, and PD-L1) that could provide additional prognostic information in Merkel cell carcinoma.

Prevalence and Viral Loads of Cutaneous Human Polyomaviruses in the Skin of Patients With Chronic Inflammatory Skin Diseases

BACKGROUND

Human skin microorganisms have been associated with various skin diseases. However, most studies have focused on bacterial communities, and little is known about normally resident skin viruses such as the Polyomaviridae and their association with cutaneous disorders.

METHODS

We investigated the infection levels of Merkel cell polyomavirus (MCPyV), human polyomavirus 6 (HPyV6), and human polyomavirus 7 (HPyV7), using triplet skin swabs collected from lesional and nonlesional skins of 86 Japanese patients with inflammatory skin diseases and mycosis fungoides, and from 149 healthy control individuals.

RESULTS

This age-matched case-control study provides the first analyses of the loads of polyomaviruses in association with various skin diseases. The viral loads were significantly higher for HPyV6/HPyV7 and lower for MCPyV in patients with psoriasis. The viral load variation was observed not only at lesion sites, but also at clinically unaffected skin sites in most of the patients. The viral strains tested were all of the Asian/Japanese genotype.

CONCLUSIONS

Our findings suggest a covariation in the infection levels of cutaneous polyomaviruses in certain inflammatory skin conditions. Worldwide prospective longitudinal studies are warranted to understand the influence of such alterations on the pathogenesis of inflammatory skin disorders.

Genetic Variability of the Noncoding Control Region of Cutaneous Merkel Cell Polyomavirus: Identification of Geographically Related Genotypes

Background

Merkel cell polyomavirus (MCPyV) is a ubiquitous cutaneous virus that causes Merkel cell carcinoma, which develops preferentially in white populations from Europe and North America. However, the genomic variations of MCPyV among ethnic groups have not been well delineated, and even less is known regarding alterations in the noncoding control region (NCCR) in the general population.

Methods

MCPyV strains recovered from skin swab specimens from 250 healthy participants with distinct ethnicities and geographic origins were subjected to sequencing analysis of the NCCR.

Results

A 25-base pair tandem repeat caused by a 25-base pair insertion within the NCCR was found predominantly in Japanese and East Asian individuals. Based on the presence of 2 other insertions and a deletion, the NCCR could be classified further into 5 genotypes. This tandem repeat was also found exclusively in the NCCR from Japanese patients with Merkel cell carcinoma, while other genotypes were detected in white patients from Europe and North America.

Conclusions

Our results suggest that the MCPyV NCCR varies according to ethnicity and that assessing the short NCCR sequence provides a rapid and simple means for identification of the Japanese and East Asian variant genotype. It remains to be established whether these NCCR variations are associated differentially with the pathogenesis of MCPyV-driven Merkel cell carcinoma between regions with varying endemicity.

PD-1 (PDCD1) promoter methylation in Merkel cell carcinoma: prognostic relevance and relationship with clinico-pathological parameters

Merkel cell carcinoma is an aggressive neuroendocrine skin tumor, for which several non-conclusive prognostic factors of adverse clinical behavior have been reported. As promoter methylation of the immune checkpoint receptor CD279/PD-1/PDCD1(mPDCD1) has been shown to be a prognostic factor in different cancers, we investigated its role in Merkel cell carcinoma. mPDCD1was assessed retrospectively in a cohort of 69 Merkel cell carcinoma patients from the University of Bologna, University of Turin and University of Insubria. Kaplan-Meier curves and log-rank tests were calculated for all variables. To assess the influence of mPDCD1, the Cox proportional hazards model and different Royston-Parmar models were evaluated. High PDCD1 methylation (mPDCD1_high) was associated with a higher overall mortality at both the univariate analysis (log rank test: χ² = 5.17, p = 0.023; permutation test: p = 0.023) and the multivariate analysis (HR = 2.111, p = 0.042). The other variables associated with a higher overall mortality at the multivariate analysis were clinical stage III-IV (HR = 2.357, p = 0.008), size > 2 cm (HR = 2.248, p = 0.031) and Merkel cell polyomavirus (HR = 0.397, p = 0.015). Further, mPDCD1_high was strongly associated with older age (81 vs 76 years, p = 0.042), absence of immune cells (92.6%, p < 0.001), no expression of PD-L1 by immune cells (70.4%, p = 0.041) and by both immune and tumor cells (70.4%, p = 0.001). mPDCD1 is a valid prognostic parameter in patients affected by Merkel cell carcinoma. In addition, it could provide an estimate of the global PD-1/PD-L1 expression with potentially relevant implications from a therapeutic point of view.

Merkel cell carcinoma. Report of a case with an atypical location and presentation

Merkel cell tumour is a rare skin tumour of high malignancy, poor prognosis and low survival. It is characterized by its tendency to lymph node and vascular invasion and by a high percentage of locoregional recurrence in the year following surgical removal. It affects adults between 60 and 80 years of age and often occurs in the head and neck. We present the case of an 85-year-old man presenting with an ulcerated gluteal mass of 4 months' evolution. Diagnosis was by histopathological and immunohistochemical study. Early diagnosis and appropriate treatment are important to improve the prognosis of these patients.

Prevalence and Genetic Variability of Human Polyomaviruses 6 and 7 in Healthy Skin Among Asymptomatic Individuals

Background

Despite the pathogenetic potential of human polyomavirus 6 (HPyV6) and human polyomavirus 7 (HPyV7), they have been found in the normal skin of healthy individuals. However, little is known about the prevalence, infection levels, and geographical variations of these polyomaviruses in the skin.

Methods

Using skin swabs from 470 participants aged 2-98 years, we estimated the prevalence of copy numbers of HPyV6 and HPyV7 with respect to age and ethnicity. Phylogenetic analyses were conducted based on viral sequences obtained from Asian and white populations.

Results

This study provides the first analyses of the age-specific prevalence and levels of HPyV6 and HPyV7 infections in normal skin. Comparisons of age groups revealed that the prevalence and viral loads were significantly higher in elderly persons. Phylogenetic analyses demonstrated the existence of Asian/Japanese-specific strains genetically distinct from strains prevalent in the skin of the white population studied.

Conclusions

This large study suggests that HPyV6 and HPyV7 infections in the skin are highly prevalent in elderly adults. Further research is warranted to understand whether persistent infection with high viral loads in the skin could be a risk factor for the development of HPyV6- and HPyV7-associated skin disorders.

Spontaneous Regression of Merkel Cell Carcinoma of the Male Breast with Ongoing Immune Response

Merkel cell carcinoma (MCC) is a rare cutaneous neuroendocrine tumor arising predominantly on sun-exposed skin among the elderly. The most common location is the head and neck, followed by the extremities. MCCs are highly aggressive tumors and rarely undergo spontaneous regression. We report a case of MCC which presented as a painless breast lump in an elderly male where the tumor regressed spontaneously after a biopsy.

Effect of Patient Immune Status on the Efficacy of Radiation Therapy and Recurrence-Free Survival Among 805 Patients With Merkel Cell Carcinoma

PURPOSE

Patients with Merkel cell carcinoma (MCC) with chronic immunosuppression (IS) have worse outcomes, but the mechanisms are not well understood. We hypothesized that these differences may be mediated in part by differential response to treatment, and we evaluated whether radiation therapy (RT) efficacy is altered among IS compared with immune-competent (IC) patients with MCC.

METHODS AND MATERIALS

Among 805 patients with MCC, recurrence-free survival (RFS) and patterns of first recurrence were compared between 89 IS and 716 IC patients with stage I to III MCC treated with curative intent. We used a Fine and Gray's competing risk multivariable analysis to estimate associations with RFS.

RESULTS

IS and IC patients with MCC had similar demographic and disease characteristics. Most (77% IC, 86% IS) were irradiated (median, 50.4 Gy IC, 50.3 Gy IS), although more IS patients were irradiated to the primary site (97% vs 81%). With a median follow-up of 54.4 months, IS patients had inferior RFS (2-year: 30% vs 57%; P < .0001) and higher rates of local recurrence as the first site of relapse (25% vs 12%; P = .0002). The association between RT and RFS differed by immune status (interaction P = .01). Although RT was associated with significantly improved RFS among IC patients (hazard ratio 0.56, 95% confidence interval 0.44-0.72), no difference in RFS was observed with RT among IS patients (hazard ratio 1.49, 95% confidence interval 0.70-3.17).

CONCLUSIONS

Radiation therapy efficacy at current standard RT doses for MCC is impaired among immunosuppressed patients with MCC. Although a strong link between durability of RT response and immune function does not appear to be evident in most cancers, our results may reflect an especially dynamic interaction between immune status and RT efficacy in MCC.

Chronic immunosuppression in the mature patient

In the ever-aging population of the world, the field of geriatrics continues to grow in importance. As human beings age, the skin undergoes a unique array of changes that predispose it to a specific set of dermatoses, infections, and neoplasms. Some of these physiologic alterations are comparable to the changes that happen in immunosuppressed individuals. Given the importance of immunosuppressive medications in treatment of many common skin conditions, we have reviewed the current literature to assist the practicing clinician in using immunosuppressive medications in the geriatric population.

Dermoscopic assessment of vascular structures in solitary small pink lesions-differentiating between good and evil

The diagnosis of a single small pink papule poses a real challenge to the clinician, as the differential diagnosis of such lesions includes benign entities such as a neurofibroma or hemangioma, as well as aggressive and potentially fatal skin malignancies such as amelanotic melanoma or Merkel cell carcinoma (MCC). The absence of a benign vascular pattern and the presence of atypical vascular features under dermoscopy direct the clinician to proceed to histologic evaluation in order to rule out a malignant process in such lesions. The diagnosis of MCC is particularly problematic, given that this tumor usually lacks specific clinical diagnostic features. Low clinical suspicion for MCC may result in delayed diagnosis and poor outcomes. The dermoscopic features of MCC are also non-specific, most commonly including milky-red areas and linear irregular vessels. We report a patient who presented with two discrete pink papules on different digits that appeared three years apart. Dermoscopy helped to diagnose a harmless hemangioma in the first lesion, and a MCC in the latter. The malignant tumor was diagnosed and excised expeditiously, with no evidence of metastatic spread.

A Review of the Global Guidelines on Surgical Margins for Nonmelanoma Skin Cancers

Background: Adequate treatment and follow-up of a patient with nonmelanoma skin cancer is of utmost concern for a clinician. However, there is a lack of international consensus on recommendations for surgical excision margins. Furthermore, lack of familiarity of the published guidelines leads to a variety in practice styles. Objective: To compare the consistency in global recommendations for surgical excision margins for basal cell carcinoma, cutaneous squamous cell carcinoma, dermatofibrosarcoma protuberans, and Merkel cell carcinoma. Methods: A review of the current literature and global guidelines for surgical excision margins for basal cell carcinoma, cutaneous squamous cell carcinoma, dermatofibrosarcoma protuberans, and Merkel cell carcinoma. Results: Upon review of international guidelines, variations do exist among guidelines for peripheral and deep surgical margins. Guideline recommendations were found to be more globally consistent in margin selection for low-risk basal cell carcinoma and low-risk cutaneous squamous cell carcinoma, however, least consistent when concerning margin selection for dermatofibrosarcoma protuberans and Merkel cell carcinoma. Conclusion: Although guidelines exist, there is a need for international collaboration and consensus to determine a more unified and evidence-based approach to surgical excision as a treatment for nonmelanoma skin cancer.

Frequency and locations of systemic metastases in Merkel cell carcinoma by imaging

Background

The primary neuroendocrine skin cancer, Merkel cell carcinoma (MCC), has a well-known predilection to metastasize systemically. However, the experience of systemic metastases in MCC is mainly disseminated through case reports due to the rarity of MCC.

Purpose

To elucidate the frequency and locations of systemic metastasis in MCC by reviewing the imaging of patients with metastatic MCC in a national cohort.

Material and Methods

Patients with diagnosed metastatic MCC by imaging studies in Finland during 1999–2012 were included in this study. We reviewed their imaging studies to evaluate the most frequent sites for systemic metastasis and determined the latency between the primary tumor diagnosis and systemic metastasis. The material includes 30 MCC patients with complete imaging series and 187 examinations, of which 102 (54%) were CT images.

Results

The mean latency from the primary tumor diagnosis to systemic metastasis was 2.1 years and the mean latency between the radiologic diagnosis of the metastases and death was 299 days. Metastases were recorded in several organ systems in most of the cases, and at least two separate metastatic sites in 63% of the cases. Metastatic spread was noted in 60% of the cases in distant lymph nodes. Liver and lungs were the most affected solid organs.

Conclusion

Systemic metastasis in MCC has no predilection site, basically every organ system can be involved. Most of the systemic metastases were recorded during the first two years after the MCC diagnosis.

Complete Spontaneous Regression of Merkel Cell Carcinoma After Biopsy: A Case Report and Review of the Literature

Merkel cell carcinoma (MCC) is a rare primary cutaneous neuroendocrine tumor that typically occurs on the head and neck of the elderly and follows an aggressive clinical course. Merkel cell polyomavirus (MCPyV) has been identified in up to 80% of cases and has been shown to participate in MCC tumorigenesis. Complete spontaneous regression of MCC has been rarely reported in the literature. We describe a case of a 79-year-old man that presented with a rapidly growing, 3-cm mass on the left jaw. An incisional biopsy revealed MCC. Additional health issues were discovered in the preoperative workup of this patient which delayed treatment. One month after the biopsy, the lesion showed clinical regression in the absence of treatment. Wide excision of the biopsy site with sentinel lymph node dissection revealed no evidence of MCC 2 months later. The tumor cells in the patient's biopsy specimen were negative for MCPyV by polymerase chain reaction and immunohistochemistry (CM2B4 antibody, Santa Cruz, CA). The exact mechanism for complete spontaneous regression in MCC is unknown. To our knowledge, only 2 previous studies evaluated the presence of MCPyV by polymerase chain reaction in MCC with spontaneous regression. Whether the presence or absence of MCPyV correlates with spontaneous regression warrants further investigation.

Shared Oncogenic Pathways Implicated in Both Virus-Positive and UV-Induced Merkel Cell Carcinomas

Merkel cell carcinoma (MCC) is a highly malignant neuroendocrine tumor of the skin whose molecular pathogenesis is not completely understood, despite the role that Merkel cell polyomavirus can play in 55-90% of cases. To study potential mechanisms driving this disease in clinically characterized cases, we searched for somatic mutations using whole-exome sequencing, and extrapolated our findings to study functional biomarkers reporting on the activity of the mutated pathways. Confirming previous results, Merkel cell polyomavirus-negative tumors had higher mutational loads with UV signatures and more frequent mutations in TP53 and RB compared with their Merkel cell polyomavirus-positive counterparts. Despite important genetic differences, the two Merkel cell carcinoma etiologies both exhibited nuclear accumulation of oncogenic transcription factors such as NFAT or nuclear factor of activated T cells (NFAT), P-CREB, and P-STAT3, indicating commonly deregulated pathogenic mechanisms with the potential to serve as targets for therapy. A multivariable analysis identified phosphorylated CRE-binding protein as an independent survival factor with respect to clinical variables and Merkel cell polyomavirus status in our cohort of Merkel cell carcinoma patients.

A high neutrophil-to-lymphocyte ratio as a potential marker of mortality in patients with Merkel cell carcinoma: A retrospective study

BACKGROUND

The prognostic relevance of a high blood neutrophil-to-lymphocyte ratio (NLR) has been reported in many cancers, although, to our knowledge, not investigated in patients with Merkel cell carcinoma (MCC) to date.

OBJECTIVE

We assessed whether the NLR at baseline was associated with specific survival and recurrence-free survival in MCC.

METHODS

We retrospectively included MCC cases between 1999 and 2015 and collected clinical data, blood cell count at baseline, and outcome. A Cox model was used to identify factors associated with recurrence and death from MCC.

RESULTS

Among the 75 patients included in the study, a high NLR at baseline (NLR ≥4) was associated with death from MCC in univariate (hazard ratio 2.76, 95% confidence interval 1.15-6.62, P = .023) and multivariate (hazard ratio 3.30, 95% confidence interval 1.21-9.01, P = .020) analysis, but not with recurrence.

LIMITATIONS

Because of the retrospective design, we excluded patients with missing data and not all confounding factors that may influence the NLR were available.

CONCLUSION

A high NLR at baseline was independently associated with specific mortality in patients with MCC. The NLR seems to constitute an easily available and inexpensive prognostic biomarker at baseline.

High load of Merkel cell polyomavirus DNA detected in the normal skin of Japanese patients with Merkel cell carcinoma

BACKGROUND

Although Merkel cell polyomavirus (MCPyV) has the potential to cause Merkel cell carcinoma (MCC), it is also found in the normal skin of healthy individuals. However, the mechanism for transformation of MCPyV to an oncogenic form is unknown.

OBJECTIVES

To investigate the levels of MCPyV infection in the normal skin patients with MCC compared with those in a control cohort.

STUDY DESIGN

We studied a total of six Japanese patients with cutaneous MCC. Sun-exposed and sun-unexposed skin swabs were obtained and analyzed for MCPyV loads using quantitative real-time polymerase chain reaction.

RESULTS

At first, we found a patient with MCC carrying an extremely high load of MCPyV DNA in normal skin. This unique case prompted us to further explore the levels of MCPyV as skin microbiota in patients with MCC. We showed that MCPyV DNA levels were significantly higher in swabs obtained from normal skin samples of six patients with MCC compared with those from 30 age-matched healthy individuals and 19 patients with other cutaneous cancers. Whereas MCPyV strains obtained from the normal skin of patients with MCC had gene sequences without structural alterations, sequences of the tumor-derived strains showed truncating mutations or deletions.

CONCLUSIONS

Although the number of patients with MCC studied was small, our findings suggest that MCC may occur with a background of high MCPyV load in the skin, and are expected to stimulate further studies on whether such skin virome levels could be one of predictive markers for the development of MCC.

Phylogenetic and structural analysis of merkel cell polyomavirus VP1 in Brazilian samples

Our understanding of the phylogenetic and structural characteristics of the Merkel Cell Polyomavirus (MCPyV) is increasing but still scarce, especially in samples originating from South America. In order to investigate the properties of MCPyV circulating in the continent in more detail, MCPyV Viral Protein 1 (VP1) sequences from five basal cell carcinoma (BCC) and four saliva samples from Brazilian individuals were evaluated from the phylogenetic and structural standpoint, along with all complete MCPyV VP1 sequences available at Genbank database so far. The VP1 phylogenetic analysis confirmed the previously reported pattern of geographic distribution of MCPyV genotypes and the complexity of the South-American clade. The nine Brazilian samples were equally distributed in the South-American (3 saliva samples); North American/European (2 BCC and 1 saliva sample); and in the African clades (3 BCC). The classification of mutations according to the functional regions of VP1 protein revealed a differentiated pattern for South-American sequences, with higher number of mutations on the neutralizing epitope loops and lower on the region of C-terminus, responsible for capsid formation, when compared to other continents. In conclusion, the phylogenetic analysis showed that the distribution of Brazilian VP1 sequences agrees with the ethnic composition of the country, indicating that VP1 can be successfully used for MCPyV phylogenetic studies. Finally, the structural analysis suggests that some mutations could have impact on the protein folding, membrane binding or antibody escape, and therefore they should be further studied.

Merkel cell carcinoma of the head and neck: challenges in implementing best practice

OBJECTIVE

Merkel cell carcinoma (MCC) is a rare, aggressive skin tumor. Controversies regarding optimal management persist due to inadequate data and knowledge regarding tumor biology. Head and neck MCC increases both oncological and reconstructive challenges, compounded by predominantly elderly patients. We review our practice and outcomes, review evidence, and discuss the difficulties in delivering best practice management.

METHODS

All patients with primary head and neck MCC, managed by a single multidisciplinary team between January 2001 and December 2010, were identified through retrospective analysis of a pathology coding database. A literature review was performed.

RESULTS

Twenty patients, with a mean age of 83.5 years (40-99 years) and presenting with mean symptom duration of 5 months, had primary tumors involving the nose (n = 2), periorbital region (n = 5), cheek (n = 6), and the temple and scalp (n = 7). Mean tumor size was 2.1 cm (range, 0.5-7.5 cm). Reconstructive techniques were direct closure (n = 8), skin grafting (n = 7), local flaps (n = 4), and free anterolateral thigh flap (n = 1). Two (10%) patients presented with nodal disease. Eight (40%) patients re-presented with nodal recurrence at a mean of 7 months with 6 undergoing salvage neck dissections. Adjuvant radiotherapy was completed in 5 cases, and chemotherapy used for palliation in 1 case. Most of the patients declined radiotherapy due to adverse effects or frailty.

CONCLUSIONS

Our series demonstrates the profound challenges in managing head and neck MCC, including tailoring definitive primary treatment and current consensus management to elderly patients. Regional nodal assessment and management remains crucial to achieving this goal.

Merkel cell carcinoma of right buttock in an elderly patient: a case report

Merkel cell carcinoma is a rare primary cutaneous tumor. So far, few cases have been reported.  Herewith we report a case of an 87-years-old male with painless, ulceroproliferative growth measuring 6x6 cm, over right upper outer quadrant of buttock; stage IIB (TNM, T3cNoMo). Patient received neo-adjuvant chemotherapy, injection of carboplatin 420 mg (day one) and etoposide 140 mg (day one to three) three weekly for three cycles followed external beam radiotherapy by Cobalt 60. At three months post-treatment follow-up, clinically no evidence of residual disease or recurrences noted. The purpose of reporting this case was to emphasize to its rarity, early asymptomatic clinical course leading to possibility of delayed diagnosis and paramount importance of high index of clinical suspicion in definitive diagnosis for better treatment result.

Somatostatin Receptors 2A and 5 Are Expressed in Merkel Cell Carcinoma with No Association with Disease Severity

BACKGROUND/AIMS

Merkel cell carcinoma (MCC) is a rare high-grade neuroendocrine tumour of the skin. It has been speculated that MCCs express somatostatin receptors (SSTRs), but this has never been assessed in a large series of MCCs. The main aim of this study was to assess the expression of SSTR2A and SSTR5 in MCC tumours. The secondary aims were to assess whether expression of SSTR was associated with the Ki67 proliferative index, Merkel cell polyomavirus (MCPyV) status, clinical characteristics and outcome.

METHODS

Clinical data and tumours were collected from an ongoing cohort of French patients with MCC. Immunohistochemistry was performed with anti-SSTR2A and anti-SSTR5 monoclonal antibodies, and tumours were classified into 3 groups: 'no expression', 'low expression' and 'moderate expression' using an SSTR staining score.

RESULTS

SSTR expression was assessed for 105 MCC tissue samples from 98 patients, and clinical characteristics were available for 87 of them. SSTR expression was consistent between the primary skin tumour and the corresponding metastases for SSTR2A and SSTR5 in 3/7 and 6/7 cases, respectively. SSTR2A and SSTR5 were expressed in 58 cases (59.2%) and in 44 cases (44.9%), respectively. Overall, at least one SSTR was expressed in 75 tumours (76.5%). SSTR expression was not associated with clinical characteristics, Ki67 proliferative index, recurrence-free survival or MCC-specific survival. Expression of SSTR2A was associated with MCPyV status in MCC tumours but not SSTR5.

CONCLUSION

SSTRs were expressed in a high proportion of MCCs, although expression was heterogeneous between tumours and was not associated with disease severity.

Concurrent chronic lymphocytic leukemia and merkel cell carcinoma in primary skin tumor and metastatic lymph node

Association between chronic lymphocytic leukemia and other malignancies has been known for a long time. This epidemiological phenomenon is explained by immunosuppression caused by disease itself or by the applied therapy. Merkel cell carcinoma is a rare malignant tumor of the skin of neuroendocrine origin diagnosed almost exclusively in immunocompromised host. We presented an unique case of coexisting infiltration of chronic lymphocytic leukemia cells within primary cutaneous Merkel cell carcinoma and metastatic lymph node in young HIV-negative female patient.

Skin cancer in kidney transplant recipients

Morbidity and mortality due to skin cancer is excessively high in renal transplant recipients compared to the general population. This epidemiologic difference is mainly due to the severe immunosuppression that enhances ultraviolet-induced DNA damage and leads to reactivation of potential oncogenic viruses. The most common skin cancer in transplant recipients is squamous cell carcinoma followed by basal cell carcinoma, while in the general population this ratio is reversed. Melanoma and cutaneous lymphoma are relatively rare although they occur more frequently in transplant patients than in the general population. Notably some tumors, such as Kaposi's sarcoma, are seldom encountered in the general population while they are frequently observed in transplant recipients. Local recurrences and visceral spreading are not so uncommon and pose a major issue for quality of life and overall prognosis of these patients. Timely diagnosis is essential and may be challenging, since the accuracy of clinical diagnosis is modest; thus skin biopsy is an essential tool for appropriate management. In this review, we describe the most common types of skin cancer in renal transplant recipients, with a focus on pathogenic issues that account for the different epidemiology and clinical expression of these neoplasms in this population.

Small Circular DNAs in Human Pathology

In general, human pathogen-related small circular deoxyribonucleic acid (DNA) molecules are bacterial plasmids and a group of viral genomes. Plasmids are extra-chromosomal small circular DNAs that are capable of replicating independently of the host, and are present throughout a variety of different microorganisms, most notably bacteria. While plasmids are not essential components of the host, they can impart an assortment of survival enhancing genes such as for fertility, drug resistance, and toxins. Furthermore, plasmids are of particular interest to molecular biology especially in relation to gene-cloning. Among viruses, genomes of anelloviruses, papillomaviruses, and polyomaviruses consist of small circular DNA. The latter two virus families are known for their potential roles in a number of pathogenic processes. Human papillomaviruses (HPV) are now widely recognised to be associated with a greatly increased risk of cervical cancer, especially oncogenic strains 16 and 18. On the other hand, human cells may contain several types of small circular DNA molecules including mitochondrial DNA (mtDNA). The mitochondrial genome consists of 37 genes that encode for proteins of the oxidation phosphorylation system, transfer ribonucleic acids (tRNAs), and ribosomal RNAs (rRNAs). Though mitochondria can replicate independently of the host; nuclear DNA does encode for several mitochondrial proteins. Mutations in mtDNA contribute to some well characterised diseases; mtDNA is also implicated in several diseases and malignancies with poorly elucidated aetiologies. Furthermore, mtDNA can function as a diagnostic tool. Other extra-chromosomal circular DNAs are usually detected in cancer. This review article is intended to provide an overview of four broad categories of small circular DNAs that are present in non-eukaryotic (plasmids and relevant viral genomes) and eukaryotic (mtDNA and other extra-chromosomal DNAs) systems with reference to human diseases, particularly cancer. For this purpose, a literature search has been carried out mainly from PubMed. Improved understanding of the significance of small circular DNA molecules is expected to have far reaching implications in many fields of medicine.

Absolute lymphocyte count: a potential prognostic factor for Merkel cell carcinoma

BACKGROUND

Absolute lymphocyte count (ALC) is a laboratory value commonly obtained during workup of patients with Merkel cell carcinoma (MCC).

OBJECTIVE

We report the prognostic impact of ALC as a surrogate of immune status in MCC.

METHODS

A complete blood cell count was available for 64 patients with MCC in the month before definitive surgery, chemotherapy, or radiation. Statistical analysis was performed with classification and regression tree analysis, log rank test, and Cox model.

RESULTS

Median overall survival (OS) for the cohort was 97 months. Median OS for patients with an ALC less than 1.1 k/mm(3) was 18.8 versus 110.1 months for those with ALC greater than or equal to 1.1 k/mm(3) (P = .002, hazard ratio 0.29). Multivariate analysis of OS controlling for ALC, sex, stage, adjuvant chemotherapy, hematologic malignancy, and immunosuppression demonstrated ALC as a prognostic factor (P = .03). Disease-free survival at 36 months for ALC less than 1.1 k/mm(3) was 26.9% versus 64.4% for those with ALC greater than or equal to 1.1 k/mm(3) (P = .01). ALC was not a significant predictor for disease-free survival on multivariate analysis (P = .12).

LIMITATIONS

This is a single-institution retrospective data set.

CONCLUSION

ALC is associated with OS but not disease-free survival in MCC using a threshold of less than 1.1 k/mm(3). This test may provide additional prognostic information for patients with MCC.

Giant Merkel cell carcinoma of the lower limb: case report and review of the literature

BACKGROUND

Merkel cell carcinoma (MCC) is a rare cutaneous neuroendocrine malignancy that usually grows rapidly at the head and neck. Giant forms at the lower limbs are rarely reported and usually affect patients in the eighth decade or older.

METHODS

We report the case of a 60-year-old man who presented with a giant MCC on his right thigh. We managed this case by applying the 2012 updated guidelines and reviewed all cases of giant MCC of the lower limbs reported in the literature.

RESULTS

At the 4-month follow-up, the patient showed complete remission.

CONCLUSION

Giant forms of MCC are still treated as typical cases of MCC, when these patients show a very poor prognosis. In young and adult people, such as our case, wide surgical excisions, sentinel lymph node biopsy in clinically negative node cases, radiotherapy of the regional drain area, and a strict follow-up should be routinely performed to improve patients' survival.

Merkel cell carcinoma: case study and literature review

Merkel cell carcinoma is a rare, aggressive, highly metastatic, often fatal, primary neuroendocrine tumor typically located on sun-exposed skin. It is frequently found in white males aged 60 to 70 years. The somewhat typical benign clinical appearance of the lesion can result in a delayed diagnosis, leading to a less than optimal outcome.

Chronic mTOR activation promotes cell survival in Merkel cell carcinoma

Merkel cell carcinoma (MCC) is an aggressive skin cancer with rising incidence. In this study, we demonstrate that mTOR activation and suppressed autophagy is common in MCCs. mTOR inhibition in two primary human MCC cell lines induces autophagy and cell death that is independent of caspase activation but can be attenuated by autophagy inhibition. This is the first study to evaluate mTOR and autophagy in MCC. Our data suggests a potential role of autophagic cell death upon mTOR inhibition and thus uncovers a previously underappreciated role of mTOR signaling and cell survival, and merits further studies for potential therapeutic targets.

Merkel cell carcinoma with divergent differentiation: histopathological and immunohistochemical study of 15 cases with PCR analysis for Merkel cell polyomavirus

AIMS

To report on 15 cases of Merkel cell carcinoma (MCC) with divergent differentiation, to characterize its clinicopathological spectrum and its relationship with Merkel cell polyomavirus (MCV).

METHODS AND RESULTS

Fifteen patients with a mean age of 81 years were included. Follow-up was available for 13 cases (range 12 days to 6 years; median 6 months). Recurrence, metastasis and mortality rates were 15.4%, 53.8% and 61.5%, respectively. All tumours showed the typical histological and immunohistochemical features of MCC, with at least one additional divergent component. Eight cases had a single aberrant component (squamous in six cases, follicular in one case, and porocarcinoma in one case), six cases had two aberrant components (squamous and sarcomatous in three cases, glandular and squamous in two cases, and sarcomatous and neuroblastic in one case), and one case had three aberrant components (glandular, squamous, and sarcomatous). All cases had dysplastic changes in the overlying epithelium, and four of 15 showed epidermotropism. PCR analysis for Merkel cell polyomavirus (MCV) gave negative results in all 12 cases tested.

CONCLUSIONS

Merkel cell carcinoma with divergent differentiation is a highly aggressive tumour that might be difficult to recognize, owing to its wide histological variability. Negativity for MCV suggests that the virus is not implicated in the development of this subtype of MCC.

Merkel cell carcinoma

Merkel cell carcinoma (MCC) is a rare, clinically aggressive cutaneous neuroendocrine neoplasm with a high mortality rate. Though the etiology is not precisely known, Merkel cell polyomavirus DNA has been found recently in a large percentage of MCC tumors. Other suggested risk factors include sun exposure, immunosuppression, and a history of prior malignancy. Work up of patients with MCC most notably includes nodal staging via clinical examination or sentinel lymph node biopsy. The prognosis for most patients with MCC is poor, and the rarity of MCC precludes the prospective, randomized clinical trials necessary to elucidate optimum treatment protocols. Most published data support the use of a multimodality approach centered around surgical excision with negative margins, sentinel lymph node biopsy to establish the presence or absence of nodal metastases, adjuvant radiothearpy to decrease the risk of recurrence, and systemic chemotherapy in the case of widespread disease.

Evidence-based management of primary and localized Merkel cell carcinoma: a review

BACKGROUND

Merkel cell carcinoma is a rare and often lethal cutaneous neuroendocrine malignancy with a tendency for early and frequent locoregional and distant metastasis and relapses. It is a tumor of the elderly and immunosuppressed, which most often appears on sun-exposed areas of the body. There is growing interest in characterization of the disease and the best approach to its management. Despite the lack of prospective randomized clinical trials, treatment is evolving.

OBJECTIVE

To provide an updated review of the most current and relevant data concerning the surgical (± radiological) management of Merkel cell carcinoma, including the role of Mohs micrographic surgery.

METHODS

Using relevant MeSH terms, we performed a review of the literature on the above subjects from 1981 to 2011.

RESULTS AND CONCLUSION

For primary tumors without evidence of organ metastases, surgical excision should be the primary therapy. Owing to the high rate of local metastases, a safety margin of at least 2 cm should be considered. In situations where small, localized tumors and/or special locations necessitate a smaller safety margin, compensation by complete histological examination of the excision margins and perhaps adjuvant radiation therapy should be undertaken. The literature states that benefits of Mohs micrographic surgery (over wide local excision) include tissue conservation and identification of tumors that may require extremely wide excision margins. The majority of data to date supports the use of Mohs surgery in the treatment of Merkel cell carcinoma.

Merkel cell polyomavirus and HPV-17 associated with cutaneous squamous cell carcinoma arising in a patient with melanoma treated with the BRAF inhibitor dabrafenib

IMPORTANCE

Approximately 10% to 25% of patients treated with BRAF inhibitors develop cutaneous squamous cell carcinoma (SCC), but the mechanism responsible has not yet been determined. We report what we believe to be the first case in which Merkel cell polyomavirus (MCPyV) and human papillomavirus subtype 17 (HPV-17) were associated with cutaneous SCC that developed during treatment with the BRAF inhibitor dabrafenib.

OBSERVATIONS

A 62-year-old woman with V600E BRAF -mutant metastatic melanoma enrolled in a phase 1 trial of dabrafenib, a selective inhibitor of V600-mutant BRAF kinase. During the first 6 weeks of treatment, the patient developed multiple skin lesions, including a 6-mm crusted papule on the left eyebrow, which was resected and, on pathology examination, revealed SCC. The DNA extracted from paraffin-embedded tissue was amplified by polymerase chain reaction for detection of MCPyV and epidermodysplasia verruciformis HPV (EV-HPV) types. Analysis of the cloned and sequenced polymerase chain reaction products revealed the presence of MCPyV and HPV-17 DNA. Other EV-HPV subtypes were not detected.

CONCLUSIONS AND RELEVANCE

To our knowledge, this is the first report demonstrating the coexistence of MCPyV and HPV-17 in cutaneous SCC. Because both viruses have oncogenic potential, their role in the development of BRAF inhibitor-related SCC merits further investigation.

Merkel cell carcinoma of left groin: a case report and literature review

Merkel cell carcinoma (MCC) is an uncommon highly aggressive skin malignancy with an increased tendency to recur locally, invade regional lymph nodes, and metastasize distally to lung, liver, brain, bone, and skin. The sun-exposed skin of head and neck is the most frequent site of involvement (55%). We report the case of a 63-year-old Caucasian male patient who presented with a recurrent left inguinal mass for the third time after surgical resection with safe margins and no postoperative radio- or chemotherapy. The presented mass was excised, and pathological diagnosis revealed recurrent MCC. The patient underwent postoperative radiation therapy, and 6 months later, he developed a right groin mass which was resected and pathological diagnosis confirmed metastatic MCC. Six months later, patient developed an oropharyngeal mass which was unresectable, and pathological biopsy confirmed metastatic MCC. Patient was offered palliative radio- and chemotherapy. In this paper, we also present a brief literature review on MCC.

Merkel cell polyomavirus is frequently detected in korean patients with merkel cell carcinoma

Background

Merkel cell carcinoma (MCC) is an increasingly common neuroendocrine cancer of the skin. Merkel cell polyomavirus (MCPyV) is one of the causative agents of MCC. The prevalence of MCPyV in primary MCC and sun-exposed non-MCC tumors has been known to have different results depending on where it was investigated.

Objective

This study assesses the prevalence of MCPyV from primary MCC and sun-exposed non-MCC tumors in Korea.

Methods

A molecular pathology study was performed on 7 tissue specimens of MCC, 1 tissue specimen of metastatic small cell carcinoma of the lung, and 32 tissue specimens of non-MCC tumors occurring from sun-exposed areas [8 basal cell carcinomas (BCCs), 8 squamous cell carcinomas (SCCs), 8 actinic keratoses (AKs), and 8 seborrheic keratoses (SKs)]. All specimens were analyzed to determine the presence of MCPyV-DNA using both polymerase chain reaction (PCR) and real-time quantitative PCR. Immunohistochemistry with monoclonal antibody of MCPyV large T antigen (CM2B4) was also conducted.

Results

Using both PCR, MCPyV sequences were detected in six of seven MCC tissue specimens (85.7%). Five (71%) of seven MCC tumors were immunoreactive for CM2B4. All five immunoreactive cases were positive for MCPyV. However, there was no association of MCPyV with BCC, SCC, AK, and SK.

Conclusion

Our results implicate that MCPyV may contribute to the pathogenesis of primary MCC, not of non-MCC skin tumors in Korea, and the persons with MCPyV infection are unusual in Korea compared to other areas.

Clinicopathologic features of primary Merkel cell carcinoma: a detailed descriptive analysis of a large contemporary cohort

BACKGROUND

Little uniformity exists in the clinical and histologic variables reported with primary Merkel cell carcinoma (MCC).

OBJECTIVE

To provide a rigorous descriptive analysis of a contemporary cohort and promote the prospective collection of detailed data on MCC for future outcome studies.

METHODS AND MATERIALS

A detailed descriptive analysis was performed for clinical and histologic features of 147 patients with 150 primary MCC tumors in a prospectively collected database from 2006 to 2010.

RESULTS

The majority (73.5%) of patients were at American Joint Committee on Cancer clinical stage I or II at presentation, 20.4% at stage III, and 6.1% at stage IV. Detailed descriptive clinical and histologic findings are presented.

CONCLUSION

Clinical and histologic profiling of primary MCC in the literature is variable and limited. Systematic prospective collection of MCC data is needed for future outcome studies and the ability to compare and share data from multiple sources for this relatively rare tumor.

The role of the immune response in merkel cell carcinoma

Merkel cell carcinoma (MCC) is an aggressive neuroendocrine skin cancer. The Merkel cell polyomavirus (MCPyV) is implicated in its pathogenesis. Immune mechanisms are also implicated. Patients who are immunosuppressed have an increased risk. There is evidence that high intratumoral T-cell counts and immune transcripts are associated with favorable survival. Spontaneous regressions implicate immune effector mechanisms. Immunogenicity is also supported by observation of autoimmune paraneoplastic syndromes. Case reports suggest that immune modulation, including reduction of immune suppression, can result in tumor regression. The relationships between MCPyV infection, the immune response, and clinical outcome, however, remain poorly understood. Circulating antibodies against MCPyV antigens are present in most individuals. MCPyV-reactive T cells have been detected in both MCC patients and control subjects. High intratumoral T-cell counts are also associated with favorable survival in MCPyV-negative MCC. That the immune system plays a central role in preventing and controlling MCC is supported by several observations. MCCs often develop, however, despite the presence of humoral and cellular immune responses. A better understanding on how MCPyV and MCC evade the immune response will be necessary to develop effective immunotherapies.