Merkel cell carcinoma: histopathologic and prognostic features according to the immunohistochemical expression of Merkel cell polyomavirus large T antigen correlated with viral load

The diagnostic utility of Merkel cell polyoma virus immunohistochemistry in cytology specimens

OBJECTIVE

Merkel cell carcinoma (MCC) is an aggressive cutaneous neuroendocrine neoplasm that predominantly affects elderly and immunocompromised patients. Merkel cell polyoma virus (MCPyV) is clonally integrated into the majority of MCCs and has been linked to patient outcomes, playing a central role in the pathogenesis of the disease. We aimed to assess the utility of MCPyV immunohistochemistry (IHC) in the diagnosis of MCC in cytology cell block specimens and correlating with clinicopathologic features.

METHODS

Fifty-three cytology samples of MCC with sufficient cell block material were stained for MCPyV by IHC and scored semi-quantitatively in extent and intensity. Morphologic mimics of MCC including small cell lung carcinoma (n = 10), non-Hodgkin lymphoma (n = 10), basaloid squamous cell carcinoma (n = 6) and other neuroendocrine carcinomas (n = 8) were stained in parallel. Positive staining was defined as >1% of the tumour cells showing at least moderate staining intensity.

RESULTS

The cytologic features of MCC were characterized by high nuclear-cytoplasmic ratios, hyperchromatic nuclei with 'salt and pepper' chromatin, and nuclear moulding. MCPyV was detected in 24 of 53 cases (45%). Staining was strong and diffuse in roughly half of the positive samples. Of the morphologic mimics, one follicular lymphoma showed strong and diffuse staining. In contrast to prior studies, we saw no association between MCPyV status and patient outcomes.

CONCLUSION

Merkel cell polyoma virus IHC is highly specific (97%) for the diagnosis of MCC in our cohort, and can serve as a useful diagnostic tool for distinguishing MCC for morphologic mimics.

Presence of Merkel cell polyomavirus DNA and large-T antigen in keratinocyte carcinomas and its correlation with immunohistochemical markers p16, p53 and ki67

BACKGROUND

Merkel cell polyomavirus (MCPyV), a human polyomavirus that is unequivocally linked to merkel cell carcinoma (MCC), has been found in association with keratinocytes carcinomas (KC), especially basal cell carcinoma (BCC) and cutaneous squamous cell carcinoma (cSCC). Nevertheless, there is scarce information about the possible involvement of MCPyV in the development of KC.

OBJECTIVES

To assess the presence of MCPyV DNA and Large-T Antigen (LT-Ag) via Polymerase Chain Reaction (PCR) and Immunohistochemistry (IHC) in cases of KC, and to correlate its presence with immunohistochemical markers p16, p53, and ki67, tumor type and subtype, sun-exposed location, and epidemiological data.

METHODS

The prevalence of MCPyV DNA, LT-Ag, and immunohistochemical markers p16, p53, and ki67 was assessed by PCR and Immunohistochemistry (IHC) in 127 cases of KC, these results were correlated with tumor type and subtype, sun-exposed location, and epidemiological data.

RESULTS

The MCPyV DNA was detected in 42.57% (43 of 101) cases by PCR, the LT-Ag was detected in 16.4% (20 of 122) of cases, p16 in 81.5% (97 of 119), p53 in 66.4% (83 of 125), ki67 in 89% (73 of 82). No correlation between MCPyV LT-Ag and DNA confronted with tumor type, subtype, location site, and immunohistochemical markers was found. A single correlation between the MCPyV LT-Ag and cSCC tumors and peri-tumoral lymphocyte cells was noted.

STUDY LIMITATIONS

Further steps need to be taken to better evaluate the MCPyV influence and its possible role in KC carcinogenesis, as the evaluation of the virus genome state, the gene sequence that encodes LT-Ag in the KC tumor cells, and in situ hybridization for viral DNA or RNA in these cells.

CONCLUSIONS

Despite the frequent detection of MCPyV in KC, the data available so far does not support the hypothesis of a causal relationship between them.

The prognostic role of PD-L1 expression and the presence of polyomavirus in Merkel cell carcinoma cases

BACKGROUND

Merkel cell carcinoma (MCC) comprises a rare malignant primary skin tumor presenting neuroendocrine differentiation. Recently, agents blocking the programmed cell death protein 1 and programmed cell death protein ligand 1 pathway (PD-1/PD-L1) have demonstrated objective and durable tumor regressions in patients presenting advanced MCC. This study aimed to describe the sociodemographic, clinical, and histopathological characteristics of MCC patients, also assessing the prevalence of PD-L1 expression and Merkel cell Polyomavirus (MCPyV), as well as their prognostic roles.

METHODS

Data from patients diagnosed with MCC between 1996 and 2019 at a reference cancer center in Rio de Janeiro, southeastern Brazil, were evaluated in a retrospective study. Tumor samples were tested for MCPyV and PD-L1 employing immunohistochemistry. Survival analyses were carried out employing the Kaplan-Meier method and curves were compared using the log-rank test. A multiple semiparametric Cox model was used. Values p < 0.05 were considered significant.

RESULTS

A total of 65 patients were included in the study, with a mean age at diagnosis of 72 (standard deviation 13.9). A total of 56.9% (37/65) of the patients were male, 86.2% (56/65) were white, and 56.9% (37/64) were illiterate or with incomplete elementary school. MCPyV immunohistochemistry was positive in 29 cases (44.6%) and PD-L1 positivity was ≥ 1% in 42 cases (64.6%). Significant associations between MCPyV and PD-L1 expression ≥ 1% (p = 0.003) and PD-L1 expression ≥ 5% (p = 0.005) were noted. Concerning the multivariate analysis, only education level and advanced MCC stage indicated statistically significant worse progression-free survival. Regarding overall survival (OS), being male, education level and advanced stage comprised risk factors. The estimated OS at 60 months for stages I to III was of 48.9% and for stage IV, 8.9%.

CONCLUSIONS

This is the first large Brazilian cohort to assess the prevalence of MCPyV in MCC tumors, as well as PD-L1 expression and their associations. No correlations were noted between MCPyV infection or PD-L1 expression and survival rates.

Merkel cell polyomavirus and its etiological relationship with skin tumors

Viruses have been frequently identified in several human neoplasms, but the etiological role of these viruses in some tumors is still a matter of controversy. Polyomaviruses stand out among the main viruses with oncogenic capacity, specifically the Merkel cell polyomavirus (MCPyV). Recent revisions in the taxonomy of polyomaviruses have divided the Polyomaviridae family into six genera, including 117 species, with a total of 14 currently known human-infecting species. Although the oncogenicity of polyomaviruses has been widely reported in the literature since 1950, the first description of a polyomavirus as an etiological agent of a neoplasm in humans was made only in 2008 with the description of MCPyV, present in approximately 80% of cases of Merkel cell carcinoma (MCC), with the integration of its genome to that of the tumor cells and tumor-specific mutations, and it is considered the etiological agent of this neoplasm since then. MCPyV has also been detected in keratinocyte carcinomas, such as basal cell carcinoma and squamous cell carcinoma of the skin in individuals with and without immunosuppression. Data on the occurrence of oncogenic viruses potentially involved in oncogenesis, which cause persistence and tissue injury, related to the Merkel cell polyomavirus are still scarce, and the hypothesis that the Merkel cell polyomavirus may play a relevant role in the genesis of other cutaneous carcinomas in addition to MCC remains debatable. Therefore, the present study proposes to explore the current knowledge about the presence of MCPyV in keratinocyte carcinomas.

Merkel cell carcinoma: an update

Merkel cell carcinoma (MCC) is an uncommon primary cutaneous neuroendocrine carcinoma associated with an adverse prognosis. In recent years, our understanding of MCC biology has markedly progressed. Since the discovery of the Merkel cell polyomavirus, it has become clear that MCC represents an ontogenetically dichotomous group of neoplasms with overlapping histopathology. Specifically, most MCCs arise secondary to viral oncogenesis, while a smaller subset is the direct result of UV-associated mutations. The distinction of these groups bears relevance in their immunohistochemical and molecular characterization, as well as in disease prognosis. Further recent developments relate to the landmark utilization of immunotherapeutics in MCC, providing optimistic options for the management of this aggressive disease. In this review, we discuss both fundamental and emerging concepts in MCC, with a particular focus on topics of practical relevance to the surgical or dermatopathologist.

Role of the Microbiota in Skin Neoplasms: New Therapeutic Horizons

The skin and the gut are regularly colonized by a variety of microorganisms capable of interacting with the immune system through their metabolites and influencing the balance between immune tolerance and inflammation. Alterations in the composition and diversity of the skin microbiota have been described in various cutaneous diseases, including skin cancer, and the actual function of the human microbiota in skin carcinogenesis, such as in progression and metastasis, is currently an active area of research. The role of Human Papilloma Virus (HPV) in the pathogenesis of squamous cell carcinoma is well consolidated, especially in chronically immunosuppressed patients. Furthermore, an imbalance between Staphylococcus spp., such as Staphylococcus epidermidis and aureus, has been found to be strongly related to the progression from actinic keratosis to squamous cell carcinoma and differently associated with various stages of the diseases in cutaneous T-cell lymphoma patients. Also, in melanoma patients, differences in microbiota have been related to dissimilar disease course and prognosis and may affect the effectiveness and tolerability of immune checkpoint inhibitors, which currently represent one of the best chances of a cure. From this point of view, acting on microbiota can be considered a possible therapeutic option for patients with advanced skin cancers, even if several issues are still open.

Near missed diagnosis of Merkel cell carcinoma in a young immunocompetent woman with a recurrent left-arm mass: A case report

Merkel cell carcinoma (MCC) is a rare, aggressive neuroendocrine cancer that primarily affects the elderly, Caucasians, and the immunocompromised. We present a rare case of an immunocompetent young Iranian (non-Caucasian) female with a small nodule on her left arm. The lesion was initially misdiagnosed as an infected cyst and was treated with antibiotics for 20 days before being surgically removed. Unfortunately, the lump regrew rapidly 2 weeks later, when she had a biopsy, which revealed stage III MCC. She was then treated with adjuvant chemoradiotherapy after a thorough surgical resection of the tumor. Despite the fact that she was in remission after completing chemotherapy courses, she developed neutropenic fever, sepsis and died from septic shock. This case emphasizes the necessity of early clinical diagnosis of MCC and obtaining a biopsy with histopathologic evaluation of rapidly evolving skin lesions suggestive of malignancy.

Prevalence of Merkel Cell Polyomavirus in Primary Eyelid Merkel Cell Carcinomas and Association With Clinicopathological Features

PURPOSE

Merkel cell polyomavirus (MCPyV) infection is a known to be a critical risk factor for the development of Merkel cell carcinoma (MCC). Various reports on cutaneous MCC have shown that the differences in clinicohistopathological characteristics depend on the presence of MCPyV, but the situation in eyelid MCC is unknown. This study aimed to assess the prevalence of MCPyV in patients with eyelid MCC and examine the clinicohistopathological characteristics of MCPyV-associated eyelid MCC.

DESIGN

Retrospective observational case series with laboratory investigations.

METHODS

Ten patients treated for eyelid MCC were included. Histopathological characteristics were examined by immunohistochemical staining using 12 antibodies. MCPyV infection was evaluated by PCR using primer sets targeting large T antigens of the MCPyV genome and by immunohistochemical staining using CM2B4 and Ab3 monoclonal antibodies. The MCPyV viral load was also quantified by PCR using 3 primer sets.

RESULTS

All patients (4 males and 6 females) were Japanese with mean age of 79 (range: 63 to 87) years. One patient died due to distant metastasis 8 months after surgery for MCC. Immunohistochemical studies showed typical MCC findings in all cases, including CK20 and neuroendocrine marker positivity. PCR and immunohistochemistry with CM2B4 and Ab3 detected MCPyV antigen in all tumors. Quantitative PCR using sT, LT4, and TAg primers yielded 0.94, 1.72, and 1.05 copies per cell, respectively.

CONCLUSION

Clinical and histopathological characteristics of 10 patients with eyelid MCC were elucidated. MCPyV infection was detected in all eyelids. These results provide insight for understanding the tumorigenesis of eyelid MCC.

Talimogene laherparepvec resulting in near-complete response in a patient with treatment-refractory Merkel cell carcinoma

Merkel cell carcinoma (MCC) is a rare and aggressive cutaneous tumour of neuroendocrine cell origin, which can grow rapidly and metastasise early. Localised disease is treated with surgery and radiotherapy. Disease that reaches a more advanced stage can be treated with a variety of different treatment modalities including surgery, radiotherapy, chemotherapy, radionuclide therapy, immunotherapy, and intralesional therapy. We report a case of a patient who had exhausted all local and systemic treatment options and who subsequently had an exceptional response to intralesional injection of Talimogene laherparepvec (TVEC).

Clinical-Pathological Evaluation and Prognostic Analysis of 228 Merkel Cell Carcinomas Focusing on Tumor-Infiltrating Lymphocytes, MCPYV Infection and ALK Expression

Merkel cell carcinoma is a rare and aggressive primary neuroendocrine carcinoma of the skin, whose pathogenesis can be traced back to UV radiation damage or Merkel cell polyomavirus (MCPyV) infection. Despite some improvements on the characterization of the disease partly due to its increased incidence, crucial pathogenetic and prognostic factors still need to be refined. A consecutive series of 228 MCC from three hospitals in Turin was collected with the aim of both analyzing the apparent increase in MCC incidence in our area and investigating the distribution and prognostic role of clinical-pathological parameters, with a focus on MCPyV status, ALK tumor expression and tumor infiltrating lymphocytes (TILs). Review of morphology and conventional immunohistochemical staining was possible in 191 cases. In 50 cases, the expression of the novel neuroendocrine marker INSM1 was additionally assessed. Fourteen cases of MCC of unknown primary skin lesion were identified and separately analyzed. While confirming an exponential trend in MCC incidence in the last decades and providing a description of histological and cytological features of a large series of MCC, the present study concludes that 1) INSM1 is a highly sensitive marker in both skin and lymph node primary MCC; 2) positive MCPyV status, brisk TILs and lower tumor size and thickness are independent positive prognostic parameters, and the combination of the former two may provide a novel tool for prognostic stratification; 3) ALK is expressed 87% of MCC and associated with positive viral status, and could represent a prognostic biomarker, if validated in larger series.

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 Carcinoma: An updated review of pathogenesis, diagnosis, and treatment options

Merkel cell carcinoma is a rare neuroendocrine carcinoma that typically appears in sun-exposed areas of the elderly. It has a poor prognosis and with its incidence projected to increase, it is vital for dermatologists to remain up to date with recent updates in this malignancy's pathogenesis and treatment. In the past few decades Merkel cell carcinoma's pathogenesis, more specifically its relation to the Merkel cell polyomavirus, has sparked further interest in the study of this carcinoma. Most cases are attributed to malignant transformation secondary to the Merkel cell polyomavirus, with a minority derived from DNA damage resulting from ultraviolet radiation. Investigators have also determined that there are immunologic influences in the development and prognosis of Merkel cell carcinoma, as individuals with HIV, solid organ transplants, and lymphoproliferative malignancies are at a greater risk of developing this carcinoma. Also, this immunologic link carries treatment value, as immunologic therapies are currently being investigated. This article provides a comprehensive review of the epidemiology and pathogenesis of Merkel cell carcinoma as well as the current treatments available and clinical trials underway. We also touch upon the updated National Comprehensive Cancer Network Clinical Practice Guidelines in Oncology in respect to its diagnosis and recommended treatment modalities.

From Merkel Cell Polyomavirus Infection to Merkel Cell Carcinoma Oncogenesis

Merkel cell polyomavirus (MCPyV) infection causes near-ubiquitous, asymptomatic infection in the skin, but occasionally leads to an aggressive skin cancer called Merkel cell carcinoma (MCC). Epidemiological evidence suggests that poorly controlled MCPyV infection may be a precursor to MCPyV-associated MCC. Clearer understanding of host responses that normally control MCPyV infection could inform prophylactic measures in at-risk groups. Similarly, the presence of MCPyV in most MCCs could imbue them with vulnerabilities that-if better characterized-could yield targeted intervention solutions for metastatic MCC cases. In this review, we discuss recent developments in elucidating the interplay between host cells and MCPyV within the context of viral infection and MCC oncogenesis. We also propose a model in which insufficient restriction of MCPyV infection in aging and chronically UV-damaged skin causes unbridled viral replication that licenses MCC tumorigenesis.

Abdominal metastases from Merkel cell carcinoma: Prevalence and presentation on CT examination in 111 patients

PURPOSE

The purpose of this study was to report the prevalence and imaging features of abdominal metastases from Merkel cell carcinoma (MCC) on computed tomography (CT) examinations.

MATERIALS AND METHODS

A total of 111 patients with MCC from two institutions were initially identified. Of these, 27 patients (27/111; 24.3%) had abdominal metastases from MCC present on CT examination. There were 19 men and 8 women with a mean age of 75  ± 10.8 (SD) years (age range: 46-92 years). CT examinations were retrospectively reviewed by two radiologists and analyzed quantitatively for the number and dimensions of abdominal metastases from MCC and qualitatively in terms of location, margins, contours, homogeneity, patterns of enhancement, vascular involvement and extension of metastases from MCC.

RESULTS

Fifteen patients (15/27; 56%) had abdominal metastatic disease at initial diagnosis and twelve (12/27; 44%) developed abdominal metastases during the course of the disease. The mean number of locations of abdominal metastases was 2.1 ± 1.12 (SD) (range: 1-5). Abdominal metastases involved abdominal lymph nodes (16/27; 59%), adrenal glands/kidneys/retroperitoneum (14/27; 52%), mesentery/peritoneum (13/27; 48%), liver (7/27; 26%) and pancreas (7/27; 26%). Vascular involvement was found in association with peritoneal/mesenteric metastases in 6/13 (46%) patients with intraperitoneal metastases or in association with abdominal lymph nodes in 4/16 (25%) patients. Ureteral encasement and/or dilatation was found in 4/14 (28%) patients with retroperitoneal metastases and 3/16 (19%) patients with abdominal lymph nodes. Metastases to the liver, pancreas, peritoneum, retroperitoneum and adrenal glands displayed internal enhancement during the arterial phase in 1/2 (50%), 4/5 (80%), 4/7 (57%) and 5/8 (62%) patients for whom arterial phase was available, respectively.

CONCLUSION

Metastases from MCC have a prevalence of 24.3% on CT examination and may involve a variety of abdominal organs, mainly lymph nodes, peritoneal and retroperitoneal structures, but also the liver and pancreas. CT features of abdominal metastases from MCC include hypervascularity during the arterial phase of enhancement and eventually vascular and ureteral involvement.

ALK is frequently phosphorylated in Merkel cell carcinoma and associates with longer survival

Merkel cell carcinoma (MCC) is a rare skin cancer with only limited therapeutic options for advanced disease. We previously showed that oncogene ALK is frequently expressed at the RNA level in MCC and further that ALK positivity by immunohistochemistry is frequent and correlates strongly with Merkel cell polyomavirus (MCPyV) positivity. In this study, we investigated whether ALK receptor is active in MCC tumor samples and MCC cell lines, and whether ALK would be a prospective treatment target in MCC. We utilized tissue microarrays constructed from 136 primary MCC tumor samples as well as nine previously established MCC cell lines to determine the presence of ALK and phosphorylated ALK (p-ALK) via immunohistochemistry. Almost half of the analyzed MCC tumors displayed ALK phosphorylation (47.8%). Analysis of MCC tumor samples revealed that the presence of p-ALK correlated to MCPyV positivity, younger age, nonexistence of metastases at diagnosis and ultimately to better MCC-specific survival. In contrast to MCC tumor samples only two out of nine MCC cell lines showed only low ALK phosphorylation by immunohistochemistry. Our study reveals clear disparity in ALK activity between patient derived tumors and cell line samples and therefore, more advanced disease models such as xenografts are necessary to resolve whether ALK is a useful treatment target in MCC.

Trends in the incidence and morbidity of Merkel cell carcinoma in Brazil

Aims: The current study aims to present epidemiologic changes and clinical aspects of Merkel cell carcinoma (MCC) in Brazil. Methods: Data were collected from the Brazilian Population-Based Cancer Registries (2000-2015) and Hospital-Based Cancer Registries (2000-2017). Results: The average age-standardized incidence rates significantly increased in men between the years 2000 (0.31/1,000,000) and 2015 (1.21/1,000,000), with an annual percentage change of 9.4 (95% CI: 4.7-14.4; p < 0.001). In women, the incidence rates rose insignificantly in the period with an annual percentage change of 3.1 (95% CI: 0.0-6.2; p < 0.10). From the hospital-based database, 881 MCC patients were identified. Most of the patients were females (51.2%), aged >60 years (82.2%), White (67.6%) and diagnosed at stages III or IV (50.5%). Conclusions: A key aspect of public health promotion is to understand the incidence and morbidity of MCC.

Virus-positive Merkel Cell Carcinoma Is an Independent Prognostic Group with Distinct Predictive Biomarkers

PURPOSE

Merkel cell carcinoma (MCC) is an aggressive cutaneous neuroendocrine carcinoma that can be divided into two classes: virus-positive (VP) MCC, associated with oncogenic Merkel cell polyomavirus (MCPyV); and virus-negative (VN) MCC, associated with photodamage.

EXPERIMENTAL DESIGN

We classified 346 MCC tumors from 300 patients for MCPyV using a combination of IHC, ISH, and qPCR assays. In a subset of tumors, we profiled mutation status and expression of cancer-relevant genes. MCPyV and molecular profiling results were correlated with disease-specific outcomes. Potential prognostic biomarkers were further validated by IHC.

RESULTS

A total of 177 tumors were classified as VP-MCC, 151 tumors were VN-MCC, and 17 tumors were indeterminate. MCPyV positivity in primary tumors was associated with longer disease-specific and recurrence-free survival in univariate analysis, and in multivariate analysis incorporating age, sex, immune status, and stage at presentation. Prioritized oncogene or tumor suppressor mutations were frequent in VN-MCC but rare in VP-MCC. TP53 mutation developed with recurrence in one VP-MCC case. Importantly, for the first time we find that VP-MCC and VN-MCC display distinct sets of prognostic molecular biomarkers. For VP-MCC, shorter survival was associated with decreased expression of immune markers including granzyme and IDO1. For VN-MCC, shorter survival correlated with high expression of several genes including UBE2C.

CONCLUSIONS

MCPyV status is an independent prognostic factor for MCC. Features of the tumor genome, transcriptome, and microenvironment may modify prognosis in a manner specific to viral status. MCPyV status has clinicopathologic significance and allows for identification of additional prognostic subgroups.

Molecular Profiling of Merkel Cell Polyomavirus-Associated Merkel Cell Carcinoma and Cutaneous Melanoma

Merkel cell carcinoma (MCC) is a rare, high-grade, aggressive cutaneous neuroendocrine malignancy most commonly associated with sun-exposed areas of older individuals. A relatively newly identified human virus, the Merkel cell polyomavirus (MCPyV) has been implicated in the pathogenesis of MCC. Our study aimed to examine nine MCC cases and randomly selected 60 melanoma cases to identify MCPyV status and to elucidate genetic differences between virus-positive and -negative cases. Altogether, seven MCPyV-positive MCC samples and four melanoma samples were analyzed. In MCPyV-positive MCC RB1, TP53, FBXW7, CTNNB1, and HNF1A pathogenic variants were identified, while in virus-negative cases only benign variants were found. In MCPyV-positive melanoma cases, besides BRAF mutations the following genes were also affected: PIK3CA, STK11, CDKN2A, SMAD4, and APC. In contrast to studies found in the literature, a higher tumor burden was detected in virus-associated MCC compared to MCPyV-negative cases. No association was identified between virus infection and tumor burden in melanoma samples. We concluded that analyzing the key morphologic and immunohistological features of MCC is critical to avoid confusion with other cutaneous malignancies. Molecular genetic investigations such as next-generation sequencing (NGS) enable molecular stratification, which may have future clinical impact.

Presence of Human Papillomavirus and Epstein-Barr Virus, but Absence of Merkel Cell Polyomavirus, in Head and Neck Cancer of Non-Smokers and Non-Drinkers

OBJECTIVE

Determine the presence and prognostic value of human papillomavirus (HPV), Epstein-Barr virus (EBV), Merkel cell polyomavirus (MCPyV), and cell cycle proteins in head and neck squamous cell carcinoma (HNSCC) of non-smokers and non-drinkers (NSND).

METHODS

Clinical characteristics and tumors of 119 NSND with HNSCC were retrospectively collected and analyzed on tissue microarrays. RNAscope in situ hybridization (ISH) was used to screen for the presence of HPV and MCPyV mRNA. Immunohistochemistry was performed for expression of p16 as surrogate marker for HPV, Large T-antigen for MCPyV, and cell cycle proteins p53 and pRb. Positive virus results were confirmed with polymerase chain reaction. For EBV, EBV encoded RNA ISH was performed. Differences in 5-year survival between virus positive and negative tumors were determined by log rank analysis.

RESULTS

All oropharyngeal tumors (OPSCC) (n = 10) were HPV-positive, in addition to one oral (OSCC) and one nasopharyngeal tumor (NPSCC). The other three NPSCC were EBV-positive. MCPyV was not detected. Patients with HPV or EBV positive tumors did not have a significantly better 5-year disease free or overall survival. Over 70% of virus negative OSCC showed mutant-type p53 expression.

CONCLUSION

In this cohort, all OPSCC and NPSCC showed HPV or EBV presence. Besides one OSCC, all other oral (n = 94), hypopharyngeal (n = 1), and laryngeal (n = 9) tumors were HPV, EBV, and MCPyV negative. This argues against a central role of these viruses in the ethiopathogenesis of tumors outside the oro- and nasopharynx in NSND. So, for the majority of NSND with virus negative OSCC, more research is needed to understand the carcinogenic mechanisms in order to consider targeted therapeutic options.

Exploring the Prognostic Role of Ki67 Proliferative Index in Merkel Cell Carcinoma of the Skin: Clinico-Pathologic Analysis of 84 Cases and Review of the Literature

The exact prediction of outcome of patients with Merkel cell carcinoma (MCC) of the skin is difficult to determine, although several attempts have been made to identify clinico-pathologic prognostic factors. The Ki67 proliferative index is a well-known marker routinely used to define the prognosis of patients with neuroendocrine neoplasms. However, its prognostic value has been poorly investigated in MCC, and available published results are often contradictory mainly because restricted to small series in the absence of standardized methods for Ki67 evaluation. For this reason, we explored the potential prognostic role of Ki67 proliferative index in a large series of MCCs using the WHO standardized method of counting positive cells in at least 500 tumor cells in hot spot areas on camera-captured printed images. In addition, since MCC may be considered as the cutaneous counterpart of digestive neuroendocrine carcinomas (NECs), we decided to stratify MCCs using the available and efficient Ki67 threshold of 55%, which was found prognostic in digestive NECs. This choice was also supported by the Youden index analysis. In addition, we analyzed the prognostic value of other clinico-pathologic parameters using both univariate and multivariate analysis. Ki67 index appeared significantly associated with prognosis at univariate analysis together with stage IV, lack of MCPyV, and p63 expression, but not at the multivariate analysis, where survival resulted independently influenced by p63 expression and tumor stage, only.

Lymphoscintigraphy for Sentinel Node Mapping in Head and Neck Cancer

The aim of this comprehensive review is to describe and analyze the role of the sentinel node mapping in head and neck cancers. For this purpose, head and neck neoplasms have been categorized in cutaneous malignancies and neoplasms of the upper aerodigestive tract. A concise description of lymphatic drainage will be the "prelude" for each section, as well as the description of the injection techniques, when specific. Concisely, the attention has been focused on detection rate of the sentinel node by lymphoscintigraphy for each cancer, and for those patients in which the sentinel lymph node has been identified, true-positives rates, false-negative rates, and overall accuracy has been pointed out. Overall, in cutaneous neoplasms of the head and neck, the detection rate is higher than 90%, however the false-negative rate is still an issue, in particular in melanoma, inducing the need for newer developments. In fact, new tracers and techniques are already available, while prospective multicenter trials exploring the outcome impact are needed in the near future. For the upper aerodigestive tract and in particular oral cavity and oropharynx, sentinel lymph node identification by lymphoscintigraphy allows avoiding unnecessary neck dissection and/or node irradiation. Even in this case, the main limit remains the risk of false-negative rates. While, for patients affected by laryngeal and hypopharyngeal cancers the data seem very limited and, although the feasibility has been demonstrated, performances of this lymphoscintigraphy still need to be confirmed by multicenter studies.

Association of Programmed Death 1 Protein Ligand (PD-L1) Expression With Prognosis in Merkel Cell Carcinoma

Background: Merkel cell carcinoma (MCC) is a rare neuroendocrine skin cancer. Prior to the advent of immunotherapy, treatment options were limited. In our study, we evaluate the impact of tumor cell PD-L1 expression and tumor immune microenvironment on survival in MCC patients who were not treated with immune checkpoint inhibitors.

Methods: Clinical data and tissue samples were collected from 78 patients with confirmed MCC treated at Dana-Farber Cancer Institute. Specimens were analyzed for the distribution of PD-L1 by immunohistochemistry staining (IHC) and standardized analysis. Results were correlated with survival data.

Results: In this study, membrane and cytoplasmic MCC tumor cell staining for PD-L1 was detected in 22.4% (15 of 67) of cases and PD-L1 staining of intratumoral microvessels and PD-L1 positive immune cells at the infiltrative margins of the tumor in 92.5% (62 of 67) of cases. In patients untreated with immune checkpoint inhibitors, median overall survival was not different for patients based on PD-L1 expression (PD-L1+ 64 months vs. PD-L1- not reached; HR = 1.26, 95% CI: 0.46–3.45; p = 0.60).

Conclusion: PD-L1 expression is frequently detected in MCC tumor cells and tumor microenvironment. PD-L1 expression did not affect prognosis in this cohort that had not received PD-1/L1 blockade.

Clinical and molecular characterization of virus-positive and virus-negative Merkel cell carcinoma

BACKGROUND

Merkel cell carcinoma (MCC) is a highly aggressive neuroendocrine carcinoma of the skin caused by either the integration of Merkel cell polyomavirus (MCPyV) and expression of viral T antigens or by ultraviolet-induced damage to the tumor genome from excessive sunlight exposure. An increasing number of deep sequencing studies of MCC have identified significant differences between the number and types of point mutations, copy number alterations, and structural variants between virus-positive and virus-negative tumors. However, it has been challenging to reliably distinguish between virus positive and UV damaged MCC.

METHODS

In this study, we assembled a cohort of 71 MCC patients and performed deep sequencing with OncoPanel, a clinically implemented, next-generation sequencing assay targeting over 400 cancer-associated genes. To improve the accuracy and sensitivity for virus detection compared to traditional PCR and IHC methods, we developed a hybrid capture baitset against the entire MCPyV genome and software to detect integration sites and structure.

RESULTS

Sequencing from this approach revealed distinct integration junctions in the tumor genome and generated assemblies that strongly support a model of microhomology-initiated hybrid, virus-host, circular DNA intermediate that promotes focal amplification of host and viral DNA. Using the clear delineation between virus-positive and virus-negative tumors from this method, we identified recurrent somatic alterations common across MCC and alterations specific to each class of tumor, associated with differences in overall survival. Finally, comparing the molecular and clinical data from these patients revealed a surprising association of immunosuppression with virus-negative MCC and significantly shortened overall survival.

CONCLUSIONS

These results demonstrate the value of high-confidence virus detection for identifying molecular mechanisms of UV and viral oncogenesis in MCC. Furthermore, integrating these data with clinical data revealed features that could impact patient outcome and improve our understanding of MCC risk factors.

DETECTing Merkel Cell Polyomavirus in Merkel Tumors

Merkel cell carcinoma (MCC) is a rare, aggressive skin cancer caused either by Merkel cell polyomavirus (MCV) T antigen expression, post-integration (~80% cases), or by UV-mediated DNA damage. Interestingly, overall survival of MCV-positive Merkel cell carcinoma patients is better, making this differential information of significant diagnostic and prognostic value. Also, MCV provides a direct target for therapy in MCC patients. Currently, the methods used for diagnosis of MCV in tumors are often discordant and unreliable. Here we used a guided molecular scissors based-DNA Endonuclease Targeted CRISPR Trans Reporter (DETECTR) technique to develop an in vitro molecular diagnostic tool for MCV-positive MCC. DETECTR couples recombinase polymerase based amplification of target MCV DNA with Cas12a mediated detection. CRISPR diagnostics couple specific detection followed by cutting of the pathogenic DNA by the Cas enzyme-gRNA complex, with non-specific cutting of ssDNA that provides a measurable visual cue. To detect MCV DNA in MCC, we designed Cas12a gRNAs targeting the MCV DNA and tested their targeting efficiency, and sensitivity using a fluorophore quencher labeled reporter assay. We show that MCV DETECTR system can detect MCV integrated in Merkel tumor rapidly, specifically and with femto-molar sensitivity. Our study is a preliminary, proof-of-principle analysis showing the use of CRISPR for MCV diagnosis. Further validation in human tumor samples is needed for its clinical use in the near future. This new system is promising and we hope it can be coupled with immunohistochemical studies to diagnose the viral status of MCC in clinics soon.

Danger is only skin deep: aggressive epidermal carcinomas. An overview of the diagnosis, demographics, molecular-genetics, staging, prognostic biomarkers, and therapeutic advances in Merkel cell carcinoma

Merkel cell carcinoma (MCC) is a high grade primary cutaneous neuroendocrine carcinoma and is among the most aggressive cutaneous malignancies. The rising incidence of MCC, together with its often rapidly aggressive course, underscore a critical need to recognize the histopathologic and the immunohistochemical features that inform its accurate diagnosis. In the current review, we summarize the current state of knowledge regarding the accurate diagnosis of MCC and the exclusion of other entities in the differential diagnosis. We provide a comprehensive review of genomic studies that identified the molecular-genetic drivers of MCC as well as a summary of studies identifying prognostic biomarkers that can facilitate risk stratification. Importantly, Merkel cell polyomavirus (MCPyV) appears to be causative in most cases of MCC and represents both a diagnostic and prognostic marker. Finally, as staging of MCC has undergone critical refinements with the introduction of the 8th Edition of the American Joint Committee on Cancer staging system, we provide an update on MCC staging. In particular, the prognostic significance of the sentinel lymph node (SLN) in MCC necessitates a systematic approach to its evaluation and diagnosis to ensure accurate and consistent risk stratification for patients, and we therefore provide a comprehensive overview of SLN evaluation in MCC. Finally, the intimate relationship between MCC and the integrity of the host immune system has led to paradigm-shifting therapeutic advances with the successful application of immune checkpoint blockade to treat patients with advanced disease, and we therefore summarize those studies and the correlative studies in which predictive biomarkers have been identified.

Contemporary Topics in Radiation Medicine: Skin Cancer

Radiation plays an important role in the management of a variety of skin cancers. This article discusses the role of radiation in the treatment of cutaneous squamous cell carcinoma, basal cell carcinoma, Merkel cell carcinoma, cutaneous T-cell lymphoma, and B-cell lymphomas.

The biology and treatment of Merkel cell carcinoma: current understanding and research priorities

Merkel cell carcinoma (MCC) is a rare and aggressive skin cancer associated with advanced age and immunosuppression. Over the past decade, an association has been discovered between MCC and either integration of the Merkel cell polyomavirus, which likely drives tumorigenesis, or somatic mutations owing to ultraviolet-induced DNA damage. Both virus-positive and virus-negative MCCs are immunogenic, and inhibition of the programmed cell death protein 1 (PD-1)–programmed cell death 1 ligand 1 (PD-L1) immune checkpoint has proved to be highly effective in treating patients with metastatic MCC; however, not all patients have a durable response to immunotherapy. Despite these rapid advances in the understanding and management of patients with MCC, many basic, translational and clinical research questions remain unanswered. In March 2018, an International Workshop on Merkel Cell Carcinoma Research was held at the US National Cancer Institute, at which academic, government and industry experts met to identify the highest-priority research questions. Here, we review the biology and treatment of MCC and report the consensus-based recommendations agreed upon during the workshop.

Merkel cell carcinoma (MCC) is a rare and aggressive form of nonmelanoma skin cancer. The availability of immune checkpoint inhibition has improved the outcomes of a subset of patients with MCC, although many unmet needs continue to exist. In this Consensus Statement, the authors summarize developments in our understanding of MCC while also providing consensus recommendations for future research.

Diagnostic accuracy of a panel of immunohistochemical and molecular markers to distinguish Merkel cell carcinoma from other neuroendocrine carcinomas

Merkel cell carcinoma is a rare neuroendocrine carcinoma of the skin mostly induced by Merkel cell polyomavirus integration. Cytokeratin 20 (CK20) positivity is currently used to distinguish Merkel cell carcinomas from other neuroendocrine carcinomas. However, this distinction may be challenging in CK20-negative cases and in cases without a primary skin tumor. The objectives of this study were first to evaluate the diagnostic accuracy of previously described markers for the diagnosis of Merkel cell carcinoma and second to validate these markers in the setting of difficult-to-diagnose Merkel cell carcinoma variants. In a preliminary set (n = 30), we assessed optimal immunohistochemical patterns (CK20, thyroid transcription factor 1 [TTF-1], atonal homolog 1 [ATOH1], neurofilament [NF], special AT-rich sequence-binding protein 2 [SATB2], paired box protein 5, terminal desoxynucleotidyl transferase, CD99, mucin 1, and Merkel cell polyomavirus-large T antigen) and Merkel cell polyomavirus load thresholds (real-time PCR). The diagnostic accuracy of each marker was then assessed in a validation set of 103 Merkel cell carcinomas (9 CK20-negative cases and 15 cases without a primary skin tumor) and 70 extracutaneous neuroendocrine carcinoma cases. The most discriminant markers for a diagnosis of Merkel cell carcinoma were SATB2, NF expression, and Merkel cell polyomavirus DNA detection (positive likelihood ratios: 36.6, 44.4, and 28.2, respectively). Regarding Merkel cell carcinoma variants, cases without a primary skin tumor retained a similar immunohistochemical  profile and CK20-negative tumors displayed a different profile (decrease frequency of NF and SATB2 expression), but Merkel cell polyomavirus DNA remained detected (78% of cases by qPCR). Moreover, 8/9 (89%) CK20-negative Merkel cell carcinoma cases but only 3/61 (5%) CK20-negative extracutaneous neuroendocrine cases were positive for at least one of these markers. In conclusion, detection of SATB2 and NF expression and Merkel cell polyomavirus DNA helps distinguish between Merkel cell carcinoma classical and variant cases and extracutaneous neuroendocrine carcinomas.

Merkel Cell Carcinoma of the Wrist: A Case Report

PURPOSE

Merkel cell carcinomas are a rare type of neuroendocrine tumors of the head, neck, and extremities commonly found in older patients. Merkel cell carcinomas present as red-to-purple and nontender nodules with or without surface ulceration, usually measuring 2 cm in diameter.

CASE PRESENTATIONS

An 83-year-old woman with a skin-colored nodule on the dorsal aspect of her right wrist was referred to our department for treatment. The regional lymph nodes were not palpable, and the positron emission tomography/computed tomography scan did not reveal any distant metastases. We conducted wide excision of the lesion and sentinel lymph node biopsy. The defect caused by the excision and partial bone resection was reconstructed using a radical forearm rotational flap and a split-thickness skin graft. Postoperatively, the patient received adjuvant radiation therapy. We observed wound healing and an absence of complications such as recurrence at 1-year follow-up.

CONCLUSIONS

Merkel cell carcinomas are rare but aggressive neuroendocrine skin cancers, which rarely occur in the upper extremity. Our treatment of nonamputative wide excision and sentinel lymph node dissection, followed by postoperative radiation therapy, showed no local or distant recurrence. Here, we review the current literature on Merkel cell carcinomas and describe our approach of treatment.

Detection of the Merkel cell polyomavirus in the neuroendocrine component of combined Merkel cell carcinoma

Merkel cell carcinoma (MCC) is an aggressive neuroendocrine carcinoma of the skin. The main etiological agent is Merkel cell polyomavirus (MCPyV), detected in 80% of cases. About 5% of cases, called combined MCC, feature an admixture of neuroendocrine and non-neuroendocrine tumor cells. Reports of the presence or absence of MCPyV in combined MCC are conflicting, most favoring the absence, which suggests that combined MCC might have independent etiological factors and pathogenesis. These discrepancies might occur with the use of different virus identification assays, with different sensitivities. In this study, we aimed to determine the viral status of combined MCC by a multimodal approach. We histologically reviewed 128 cases of MCC and sub-classified them as "combined" or "conventional." Both groups were compared by clinical data (age, sex, site, American Joint Committee on Cancer [AJCC] stage, immunosuppression, risk of recurrence, and death during follow-up) and immunochemical features (cytokeratin 20 and 7, thyroid transcription factor 1 [TTF1], p53, large T antigen [CM2B4], CD8 infiltrates). After a first calibration step with 12 conventional MCCs and 12 cutaneous squamous cell carcinomas as controls, all eight cases of combined MCC were investigated for MCPyV viral status by combining two independent molecular procedures. Furthermore, on multiplex genotyping assay, the samples were examined for the presence of other polyoma- and papillomaviruses. Combined MCC differed from conventional MCC in earlier AJCC stage, increased risk of recurrence and death, decreased CD8 infiltrates, more frequent TTF1 positivity (5/8), abnormal p53 expression (8/8), and frequent lack of large T antigen expression (7/8). With the molecular procedure, half of the combined MCC cases were positive for MCPyV in the neuroendocrine component. Beta papillomaviruses were detected in 5/8 combined MCC cases and 9/12 conventional MCC cases. In conclusion, the detection of MCPyV DNA in half of the combined MCC cases suggests similar routes of carcinogenesis for combined and conventional MCC.

Proceedings of the NASHNP Companion Meeting, March 18th, 2018, Vancouver, BC, Canada: Salivary Neuroendocrine Carcinoma-An Overview of a Rare Disease with an Emphasis on Determining Tumor Origin

Salivary neuroendocrine carcinomas are rare and the overwhelming majority is high-grade. The parotid gland is the most commonly involved site followed by the submandibular gland. Most arise de novo but rare examples occurring as a high-grade transformation of another type of salivary gland neoplasm exist. There is significant morphologic and immunophenotypic overlap with neuroendocrine carcinomas of other sites, especially the skin. Like cutaneous neuroendocrine (or Merkel cell) carcinomas, approximately three-fourths are cytokeratin 20 positive. Cytokeratin 20 positive salivary neuroendocrine carcinomas are often referred to as being of the 'Merkel cell type' since most other non-cutaneous neuroendocrine carcinomas are cytokeratin 20 negative. Salivary neuroendocrine carcinomas may be challenging to separate from Merkel cell carcinomas of the head and neck on pathologic grounds because the latter often metastasize to the parotid gland. Clinical history is often relied upon to separate primary salivary tumors from cutaneous metastases but may not be helpful in all cases. Here we review the clinical, pathologic and molecular features of salivary neuroendocrine carcinomas focusing on high-grade major salivary gland tumors. The difficulty in separating salivary tumors from metastatic Merkel cell carcinoma will be highlighted.

Update on Merkel Cell Carcinoma

Merkel cell carcinoma (MCC) is an aggressive cutaneous neuroendocrine carcinoma. Incidence of MCC continues to rise, and risk factors include advanced age, pale skin, chronic sun exposure, and immune suppression. Diagnosing MCC utilizes a combination of morphology and immunohistochemistry. Merkel cell polyomavirus (MCPyV) is present in approximately 70-80% of MCCs and represents a key pathogenic driver in those MCCs. In contrast, MCPyV-negative MCCs arise through progressive accumulation of ultraviolet-light induced somatic mutations. Staging of MCC proceeds according to the American Joint Commission on Cancer (AJCC) 8th Edition, which utilizes features of the primary tumor together with regional lymph node(s) (clinically and/or pathologically detected) and/or distant metastases. Many potentially useful biomarkers have been studied to refine risk stratification in MCC. In recent years, the host immune infiltrate has been leveraged as immune checkpoint blockade has emerged as an efficacious mode of treatment for patients with advanced MCC.

Novel Treatment of Small-Cell Neuroendocrine of the Vagina

BACKGROUND

Primary vaginal small-cell neuroendocrine carcinoma is an extremely rare and highly aggressive malignancy. Eighty-five percent of patients die within one year of diagnosis from metastatic disease despite multimodal therapy. Gene expression profiling of tumor tissue may be useful for treatment options for various malignancies.

CASE

A 34-year-old nulliparous woman was diagnosed with primary vaginal small-cell neuroendocrine carcinoma. Twenty weeks after the initial visit, she was diagnosed with recurrence and started on chemoradiation based on the results of gene expression profile of tumor tissue. She died 34 months after the initial visit and had a 14-month progression-free survival (PFS).

CONCLUSION

Gene expression profile of tumor tissue in the management of primary vaginal small-cell neuroendocrine carcinoma may be helpful in extending progression-free survival.

[Practices in infectious pathology in France in 2015. Results of the national survey]

Pathologists have been, are and will be always implicated in the diagnosis of infectious and tropical diseases. The resurgence of opportunistic infections due to the development of immunosuppressive drugs, the increase of migratory involvements draining tropical infections and the last epidemics spotlight the importance of pathologists in the field of infectious diseases. However, cancer is nowadays the first preoccupation of pathologists, which is constantly subject to evaluate diagnostic and prognostic markers and factors predictive to targeted therapy response or immunotherapy. As tumor pathology, infectious diseases require more sophisticated and rapidly changing complementary techniques, appraisals and perhaps a national network of diagnosis. The infectious pathology club committee carries out here a census of methods used in the diagnosis of infectious diseases in France in 2015 and particularly the different techniques used by laboratories to perform infectious diseases diagnosis. This will lay down the foundation of a future national organization of the infectious pathology in providing efficient services (diagnostic support, complementary tools) for the community of French pathologists in this specific domain of competence.

Merkel cell carcinoma: Epidemiology, pathogenesis, diagnosis and therapy

Merkel cell carcinoma (MCC) is a rare and aggressive skin cancer with a neuroendocrine phenotype. Incidence varies according to the geographic regions but is overall increasing. Different risk factors have been identified namely advanced age, immunosuppression, and ultraviolet light exposure. An association between MCC and polyomavirus infection is known. However, the exact mechanism that leads to carcinogenesis is yet to be fully understood. Surgery when feasible is the recommended treatment for localized disease, followed by adjuvant radiation or chemoradiation. In the metastatic setting, chemotherapy has been the standard treatment. However, two recently published trials with immune checkpoint inhibitors in first and second line showed promising results with a tolerable safety profile and these might become the standard therapy shortly. Somatostatin receptors are expressed in many MCC but such expression is not associated with disease severity. Presently there are no biomarkers predictive of response that could help to better select patients to these new therapies, and additional research is essential.

The diagnostic utility of Merkel cell polyomavirus immunohistochemistry in a fine needle aspirate of metastatic Merkel cell carcinoma of unknown primary to the pancreas

Merkel cell carcinoma (MCC) is an aggressive skin tumor with a high tendency for metastases. We report a case of MCC initially presenting as axillary and pancreatic metastases. A 33-year-old HIV-positive Hispanic male presented with a history of a rapidly growing axillary mass. A needle core biopsy demonstrated an epithelioid neoplasm composed of small to medium-sized cells with high nuclear-cytoplasmic ratio, nuclear molding, and frequent mitotic figures. A subsequent PET scan revealed a 1.5 cm FDG avid mass in the pancreas. Endoscopic ultrasound-guided FNA of the pancreatic mass showed neoplastic cells with similar morphology to those of the axillary mass. The tumor cells were positive with pancytokeratin AE1/AE3, CK20, CD56, synatophysin, chromogranin, and Merkel cell polyomavirus (MCPyV). This case of MCC most likely originated from a resolved primary skin lesion drained by the involved axillary lymph node with subsequent metastases to the pancreas and distant lymph nodes.

Expression of Merkelcell polyomavirus (MCPyV) large T-antigen in Merkel cell carcinoma lymph node metastases predicts poor outcome

Background

The aim of this study was to determine the prevalence of MCPyV in Merkel cell carcinoma (MCC) primaries versus lymph node metastasis and to evaluate possible prognostic factors.

Methods

Samples of MCC primaries and lymph node metastases were stained immunohistochemically for the MCPyV large T-antigen and expression was compared to patients´ clinical outcome.

Results

41 MCC patients were included. 33 (61%) out of 54 specimens were MCPyV-positive in the immunohistochemistry. 15 (47%) out of 32 primary tumors were positive compared to 18 (82%) out of 22 lymph node metastases. Eleven patients with positive polyomavirus expression died from the carcinoma compared to 4 patients without virus expression. Cox regression analysis showed worse disease-free survival in patients with MCPyV compared to virus-negative lymph nodes (p = 0.002).

Conclusions

To our knowledge this is the first study to describe a negative prognostic effect of the MCPyV expression in lymph node metastasis in MCC patients.

Increased expression of EZH2 in Merkel cell carcinoma is associated with disease progression and poorer prognosis

Enhancer of zeste homolog 2 (EZH2) is a histone methyltransferase that affects tumorigenesis by epigenetic gene silencing. Merkel cell carcinoma (MCC) is a rare cutaneous neuroendocrine carcinoma that has a high risk of disease progression with nodal and distant metastases. Here, we evaluated EZH2 expression by immunohistochemistry in a cohort of 85 MCC tumors (29 primary tumors, 41 lymph node metastases, 13 in-transit metastases, and 2 distant metastases) with clinical follow-up. We show strong/moderate EZH2 expression in 54% of tumors. Importantly, weak expression of EZH2 in the primary tumor, but not nodal metastases, correlated with improved prognosis compared to moderate/strong EZH2 expression (5-year MCC-specific survival of 68% versus 22%, respectively, P=.024). In addition, EZH2 was expressed at higher levels in nodal metastases compared to primary tumors (P=.005). Our data demonstrate that EZH2 has prognostic value and may play an oncogenic role in MCC.

Seeking Standards for the Detection of Merkel Cell Polyomavirus and its Clinical Significance

Merkel cell carcinoma is a rare skin cancer associated with Merkel cell polyomavirus in most cases. Prior studies associating Merkel cell carcinoma viral status with prognosis have inconsistent findings. Moshiri et al. used multimodal virus detection to determine that the 81% of patients with virus-positive Merkel cell carcinoma tumors had earlier stage disease and better outcomes relative to virus-negative cases.

EUS-FNA of the Merkel cell carcinoma metastasis to the pancreas: Cytomorphology and immunocytochemistry on direct cytological smears

OBJECTIVE

To report two cases of Merkel cell carcinoma (MCC) metastatic to the pancreas diagnosed with endoscopic ultrasound-guided-fine needle aspiration (EUS-FNA) and to add the case of concomitant chronic lymphocytic leukaemia/small lymphocytic lymphoma (CLL/SLL) and MCC to the literature. The aim is to alert the cytopathologists once more to the problems of differential diagnosis of pancreatic metastasis of MCC and to describe the possibilities of ancillary methods performed on direct cytological smears.

METHODS

EUS-FNA procedures were performed according to standard institution protocol, using 22-G needles with cytopathologist on-site. Based on rapid on-site evaluation (ROSE), additional passes were made for immunocytochemistry (ICC). A mini panel of antibodies was used to aid the differential diagnosis.

RESULTS

Smears revealed a dispersed pattern of small round cells with scant cytoplasm, round nuclei with inconspicuous nucleoli and occasional nuclear moulding, suspicious of small cell carcinoma. Results of ICC applied to the direct cytological smears were as follows: LCA negative, Cytokeratin (clone MNF116) positive, TTF-1 negative, CD 56 positive, NSE weakly positive, Chromogranin A weakly positive and CK20 positive, in one case in a dot-like perinuclear pattern. The diagnosis of MCC was made.

CONCLUSION

Increasing incidence of MCC warrants the inclusion of MCC in the differential diagnosis of tumours of small round blue cell morphology even in unusual sites. The cytomorphological features coupled with an ICC panel are usually enough to make a confident diagnosis of MCC. EUS-FNA is a minimally invasive technique which enables sampling adequate tissue for all the ancillary methods eventually needed to support the diagnosis.

Update on Merkel Cell Carcinoma

Merkel cell carcinoma (MCC) is a rare, aggressive cutaneous neuroendocrine malignancy. Merkel cell polyomavirus, a tumorigenic DNA virus, is present in most MCC tumors, with implications for tumor biology, diagnosis, and management. Merkel cell polyomavirus-negative tumors have a high burden of UV-signature mutations, similar to melanoma. The histopathologic diagnosis of MCC requires immunohistochemistry to exclude morphologically similar entities. Therapies for advanced disease are currently lacking. Here, the features of MCC are reviewed, including recent molecular discoveries with implications for improved therapy for advanced disease.

Age and Gender Associations of Virus Positivity in Merkel Cell Carcinoma Characterized Using a Novel RNA In Situ Hybridization Assay

Purpose: Merkel cell carcinoma (MCC) is a highly aggressive neuroendocrine tumor of the skin. Merkel cell polyomavirus (MCPyV) plays an oncogenic role in the majority of MCCs. Detection of MCPyV in MCCs has diagnostic utility and prognostic potential. We investigated whether RNAscope, an RNA in situ hybridization (ISH) assay for detection of RNA transcripts in tissues, is useful for MCPyV detection.Experimental Design: We applied an RNAscope probe targeting MCPyV T antigen transcripts on tissue microarrays (TMA) and whole-tissue sections encompassing 87 MCCs from 75 patients, 14 carcinomas of other types, and benign tissues. For comparison, qPCR was performed on 57 cases of MCC from 52 patients.Results: RNA-ISH demonstrated the presence of MCPyV in 37 of 75 cases (49.3%). Notably, tumors from younger patients (<73 years) had a significantly higher virus positivity than those from elderly patients (≥73 years; 64.9% vs. 34.2%, P = 0.011). Female patients had a higher positive rate of MCPyV than male patients (66.7% vs. 39.6%, P = 0.032). Data from both RNA-ISH and qPCR were available for 57 samples. Considering MCPyV qPCR as the gold standard for determining MCPyV status, RNAscope had 100% sensitivity and 100% specificity. There was a strong correlation between qPCR copy number and RNA-ISH product score (Spearman correlation coefficient R² = 0.932, P < 0.0001).Conclusions: RNA-ISH is comparably sensitive to qPCR for detection of MCPyV and allows for correlation with tissue morphology. This study also reveals a significant association between age, gender, and MCPyV positivity. Clin Cancer Res; 23(18); 5622-30. ©2017 AACR.

New developments in the biology and the treatment of metastatic Merkel cell carcinoma

PURPOSE OF REVIEW

Patients with stage IIIB und IV metastatic Merkel cell carcinoma (mMCC), who are not suitable candidates for surgery or radiotherapy, are unlikely to achieve lasting remission or tumor control by chemo or targeted therapy. In the majority of cases, the tumor arises from viral carcinogenesis associated with the Merkel cell polyomavirus (MCPyV). In MCPyV-negative tumors with a presumable ultraviolet carcinogenesis, a high mutational burden resulting in neoantigens was discovered. In two phase II clinical trials in either the first or second-line setting, a high response rate was observed for immunotherapies with antibodies blocking the programmed death-1 (PD-1) and programmed death ligand-1 (PD-L1) immune checkpoints.

RECENT FINDINGS

The response rate was 56% with the anti-PD-1 inhibitor pembrolizumab as a first-line and 32% with the anti-PD-L1 antibody avelumab used as second-line therapy. Both treatments were well tolerated. Treatment response was rapid and in most cases maintained during follow-up, which, however, is still rather short. Whether the MCPyV or the PD-L1 status is predictive for treatment response and progression-free survival is still ambiguous. Additionally, clinical criteria for patient selection for immunotherapy of mMCC have not yet been defined.

SUMMARY

PD-1/PD-L1 inhibition can be regarded as new first-line therapy for patients with mMCC not amendable by surgery and/or radiation.

Aberrant expression of ALK and EZH2 in Merkel cell carcinoma

BACKGROUND

Distinct characteristic features categorize Merkel cell carcinoma (MCC) into two subgroups according to the Merkel cell polyomavirus infection. Many mutational studies on MCC have been carried out in recent years without identifying a prominent driver mutation. However, there is paucity reporting the expression of cancer genes at the RNA level in MCC tumors. In this study, we studied the RNA expression profiles of 26 MCC tumors, with a goal to identify prospective molecular targets that could improve the treatment strategies of MCC.

METHODS

RNA expression of 50 cancer-related genes in 26 MCC tumors was analyzed by targeted amplicon based next-generation sequencing using the Ion Torrent technology and the expression compared with that of normal, non-cancerous skin samples. Sequencing data were processed using Torrent Suite™ Software. Expression profiles of MCV-negative and MCV-positive tumors were compared. Fluorescence in situ hybridization was performed to study ALK rearrangements and immunohistochemistry to study ALK expression in tumor tissue.

RESULTS

ALK, CDKN2A, EZH2 and ERBB4 were overexpressed, and EGFR, ERBB2, PDGFRA and FGFR1 were underexpressed in MCC tumors compared to normal skin. In the MCV-negative tumors, MET, NOTCH1, FGFR3, and SMO were overexpressed and JAK3 and NPM1 were under-expressed compared to the MCV-positive tumors.

CONCLUSIONS

High expression of ALK, CDKN2A and EZH2 was recorded in MCC tumors. No ALK fusion was seen by FISH analysis. Overexpression of EZH2 suggests its potential as a drug target in MCC.

History of chronic inflammatory disorders increases the risk of Merkel cell carcinoma, but does not correlate with Merkel cell polyomavirus infection

Background:

We aimed to assess the connection between chronic inflammatory disorders (CIDs) and Merkel cell carcinoma (MCC).

Methods:

Merkel cell carcinoma cases diagnosed in 1978–2009 were extracted from the Finnish Cancer Registry and controls from the Population Registry. Information on reimbursed CIDs was linked to clinicopathological data including Merkel cell polyomavirus (MCV) status by qPCR and immunohistochemistry for the large T antigen of MCV (LTA), Ki-67 and tumour-infiltrating lymphocytes.

Results:

Chronic inflammatory disorders increased the risk of MCC significantly (odds ratio (OR) 1.39, 95% confidence interval (CI) 1.03–1.88), specifically connective tissue/systemic diseases (OR 1.75, 95% CI 1.09–1.80) and diabetic conditions (OR 1.51, 95% CI 1.03–2.22). Chronic inflammatory disorders associated with larger tumour diameter (P=0.02) and higher Ki-67 expression (P=0.005). The expression of LTA was seen significantly more often in the absence of CIDs (P=0.05).

Conclusions:

Patients with CID are at significantly higher risk for aggressive MCC. Merkel cell polyomavirus positivity is more common in MCC patients unafflicted by CID.

Polyomavirus-Negative Merkel Cell Carcinoma: A More Aggressive Subtype Based on Analysis of 282 Cases Using Multimodal Tumor Virus Detection

Previous studies have reached conflicting conclusions regarding the proportion of Merkel cell carcinomas (MCCs) that contain the Merkel cell polyomavirus (MCPyV) and the clinical significance of tumor viral status. To address these controversies, we detected MCPyV large T antigen using immunohistochemistry with two distinct antibodies and MCPyV DNA using quantitative PCR. Tumors were called MCPyV-positive if two or more of these three assays indicated presence of this virus. A total of 53 of 282 (19%) MCC tumors in this cohort were virus-negative using this multimodal system. Immunohistochemistry with the CM2B4 antibody had the best overall performance (sensitivity = 0.882, specificity = 0.943) compared with the multimodal classification. Multivariate analysis including age, sex, and immunosuppression showed that, relative to MCC patients with virus-positive tumors, virus-negative MCC patients had significantly increased risk of disease progression (hazard ratio = 1.77, 95% confidence interval = 1.20-2.62) and death from MCC (hazard ratio = 1.85, 95% confidence interval = 1.19-2.89). We confirm that approximately 20% of MCCs are not driven by MCPyV and that such virus-negative MCCs, which can be quite reliably identified by immunohistochemistry using the CM2B4 antibody alone, represent a more aggressive subtype that warrants closer clinical follow-up.