Histological, immunohistological, and clinical features of merkel cell carcinoma in correlation to merkel cell polyomavirus status

Metastatic merkel cell carcinoma to the thyroid gland: Case report and review of the literature

BACKGROUND

Merkel cell carcinoma (MCC) is an aggressive and rare neuroendocrine tumor, accounting for less than 1% of skin cancers. Metastasis primarily manifests in the cervical lymph nodes but rarely affect the thyroid.

METHODS

We report a case of primary head and neck cutaneous MCC with metastasis to the thyroid gland. A review of the literature of MCC with thyroid metastasis was conducted.

RESULTS

We identified five cases of MCC with thyroid metastasis. Primary sites included the distal upper and lower extremities, axilla, buttock, and groin. Treatment courses varied including thyroidectomy, immunotherapy, and expectant palliative measures. Time from initial diagnosis to thyroid metastasis ranged from four months to four years. Tissue diagnosis was achieved in 5 of 6 cases.

CONCLUSIONS

MCC with thyroid metastasis is rare and likely represents aggressive disease. Despite advances in treatment and surveillance, outcomes for MCC remain poor. Ongoing research may establish predictors for treatment response.

[Periocular Merkel Cell Carcinoma - an overview of clinical aspects and current therapeutic options]

Merkel cell carcinoma (MCC) is a rare but highly aggressive and rapidly expanding malignant skin tumor. It affects the periocular region in approximately 10% of cases. The current treatment recommendation for resectable non-metastatic MCC comprises total surgical excision; however, lymph node or distant metastases are often already present by the time of the diagnosis. Since an immune checkpoint inhibitor therapy with avelumab was first approved for MCC in 2016, there has been considerable improvement in mean survival compared to cytostatic therapy; at the same time, there has been a reduction in serious treatment-associated adverse events. Other immune checkpoint inhibitors are currently still in clinical trials, with very promising initial results. Because of the complexity of the diagnosis, treatment, and prognosis, it is essential that MCC patients receive interdisciplinary care in a specialized center including consultation with a tumor review board.

Moderne Diagnostik und Therapie des Merkelzellkarzinoms

Das Merkelzellkarzinom (MCC) ist ein seltener, aggressiver Hauttumor mit epithelialer und neuroendokriner Differenzierung, dessen Inzidenz in den letzten Jahrzehnten deutlich zugenommen hat. Risikofaktoren sind fortgeschrittenes Lebensalter, heller Hauttyp, UV‐Exposition und Immunsuppression. Pathogenetisch wird ein durch das Merkelzell‐Polyomavirus (MCPyV) hervorgerufener Typ von einem UV‐induzierten Typ mit hoher Tumormutationslast unterschieden.

Klinisch präsentiert sich das MCC als meist schmerzloser, schnell wachsender, rötlich‐violetter Tumor mit glänzender Oberfläche, der bevorzugt im Kopf‐Hals‐Bereich und an den distalen Extremitäten lokalisiert ist. Eine sichere Diagnose kann nur anhand histologischer und immunhistochemischer Merkmale gestellt werden. Bei Erstdiagnose weisen 20%–26% der Patienten lokoregionäre Metastasen und 8%–14% Fernmetastasen auf, weshalb eine Ausbreitungsdiagnostik unabdingbar ist. Bei fehlenden klinischen Hinweisen auf Metastasen wird eine Sentinel‐Lymphknotenbiopsie empfohlen.

Wesentliche Säulen der Therapie sind die Operation, die adjuvante oder palliative Strahlentherapie und in fortgeschrittenen inoperablen Stadien die medikamentöse Tumortherapie. Die Einführung von Immuncheckpoint‐Inhibitoren führte zu einem Paradigmenwechsel, da sich hiermit ein wesentlich langfristigeres Ansprechen und bessere Überlebensraten als mit Chemotherapie erreichen lassen. Zur Therapie des metastasierten MCC ist in Deutschland der PD‐L1‐Inhibitor Avelumab zugelassen, aber auch die PD‐1‐Antikörper Pembrolizumab und Nivolumab werden mit Erfolg eingesetzt. Adjuvante und neoadjuvante Therapiekonzepte, Immunkombinationstherapien und zielgerichtete Therapien als Monotherapie oder in Kombination mit Immuncheckpoint‐Inhibitoren befinden sich in klinischer Prüfung.

Modern diagnostics and treatment of Merkel cell carcinoma

Merkel cell carcinoma (MCC) is a rare, aggressive skin cancer with epithelial and neuroendocrine differentiation, the incidence of which has increased substantially during the last decades. Risk factors include advanced age, fair skin type, UV exposure, and immunosuppression. Pathogenetically, a type caused by the Merkel cell polyomavirus is distinguished from a UV-induced type with a high tumor mutational burden. Clinically, MCC presents as a mostly painless, rapidly growing, reddish-violet tumor with a shiny surface, which is preferentially localized in the head-neck region and at the distal extremities. A reliable diagnosis can only be made based on histological and immunohistochemical features. At initial diagnosis, 20-26% of patients show locoregional metastases and 8-14% distant metastases, making staging examinations indispensable. If there is no clinical evidence of metastases, a sentinel lymph node biopsy is recommended. Essential columns of therapy are surgery, adjuvant or palliative radiotherapy and, in advanced inoperable stages, medicamentous tumor therapy. The introduction of immune checkpoint inhibitors has led to a paradigm shift, as they provide a considerably longer duration of response and better survival rates than chemotherapy. The PD-L1 inhibitor avelumab is approved for treatment of metastatic MCC in Germany, but the PD-1 antibodies pembrolizumab and nivolumab are also used with success. Adjuvant and neoadjuvant treatment concepts, immune combination therapies and targeted therapies as monotherapy or in combination with immune checkpoint inhibitors are in the clinical trial phase.

The Evaluation and Treatment of Merkel Cell Carcinoma and Brain Metastasis: A Case Report and Review of the Literature

Merkel cell carcinoma (MCC) is a rare and aggressive neuroendocrine tumor associated with high mortality if metastases are identified. Currently, there is no standardized nor curative treatment for neurometastatic MCC. In this study, we have reviewed the more recent cases and the use of immunotherapy in a population. In this case report and review, we present a case of MCC with brain metastasis currently undergoing treatment with immunotherapy (pembrolizumab) resulting in an initial complete response with a progression-free survival time of five months. We also review the past reported literature and the 11 newly presented cases on their clinical presentation of neurometastatic MCC, immunohistochemical markers, and treatment outcomes. In summary, immunotherapy initially showed a promising response with the complete elimination of MCC brain metastasis. The early aggressive treatment of pembrolizumab with stereotactic radiosurgery should be considered as this treatment plan has shown improved therapeutic effects compared to the standard chemoradiation therapy. Further investigations are needed to determine the efficacy and response of immunotherapy use for neurometastatic MCC.

A review of Merkel cell carcinoma

ABSTRACT

Merkel cell carcinoma (MCC) is a rare and aggressive type of metastatic, nonmelanoma skin cancer derived from Merkel cells in the epidermis. MCC can be induced by sun exposure or via Merkel cell polyomavirus (MCV) gene expression. MCV is found in most patients with MCC and is associated with a lower recurrence rate of MCC. MCC has a wide range of clinical presentations that make diagnosis challenging. Histologic examination is performed using unique markers to differentiate it from other diagnoses. This article reviews the pathogenesis, clinical presentation, histopathology, differential diagnosis, and treatment of MCC.

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.

Periocular Merkel Cell Carcinoma - An Overview of Clinical Aspects and Current Treatment Options

Merkel cell carcinoma (MCC) is a rare but highly aggressive and rapidly expanding malignant skin tumor. It affects the periocular region in approximately 10% of cases. The current treatment recommendation for resectable non-metastatic MCC comprises total surgical excision; however, lymph node or distant metastases are often already present by the time of the diagnosis. Since an immune checkpoint inhibitor therapy with avelumab was first approved for MCC in 2016, there has been considerable improvement in mean survival compared to cytostatic therapy; at the same time, there has been a reduction in serious treatment-associated adverse events. Other immune checkpoint inhibitors are currently still in clinical trials, with very promising initial results. Because of the complexity of the diagnosis, treatment, and prognosis, it is essential that MCC patients receive interdisciplinary care in a specialized center including consultation with a tumor review board.

Merkel Cell Polyomavirus (MCPyV) and Cancers: Emergency Bell or False Alarm?

Merkel cell polyomavirus (MCPyV), the sole member of Polyomavirus associated with oncogenesis in humans, is the major causative factor of Merkel cell carcinoma (MCC), a rare, neuroendocrine neoplasia of the skin. Many aspects of MCPyV biology and oncogenic mechanisms remain poorly understood. However, it has been established that oncogenic transformation is the outcome of the integration of the viral genome into the host DNA. The high prevalence of MCPyV in the population, along with the detection of the virus in various human tissue samples and the strong association of MCPyV with the emergence of MCC, have prompted researchers to further investigate the role of MCPyV in malignancies other than MCC. MCPyV DNA has been detected in several different non-MCC tumour tissues but with significantly lower prevalence, viral load and protein expression. Moreover, the two hallmarks of MCPyV MCC have rarely been investigated and the studies have produced generally inconsistent results. Therefore, the outcomes of the studies are inadequate and unable to clearly demonstrate a direct correlation between cellular transformation and MCPyV. This review aims to present a comprehensive recapitulation of the available literature regarding the association of MCPyV with oncogenesis (MCC and non-MCC tumours).

Development of Merkel Cell Carcinoma in a Patient Receiving Rituximab

Merkel cell carcinoma (MCC) is a rare, rapidly growing, and aggressive dermatological neoplasm. It is commonly reported in Caucasian ethnicities, and almost 50% of the patients have a concomitant malignancy and are on immunosuppressive chemotherapy. Here, we present a 79-year-old woman with a history of relapsed Stage II, grade III follicular lymphoma, receiving maintenance rituximab infusions. She presented with a raised erythematous papule on her left cheek. An excisional biopsy of the lesion confirmed a diagnosis of Merkel cell carcinoma. After which, she underwent a wider excision with 1-2 cm margins. PET scan did not reveal any FDG-avid uptake lesions that would be concerning for metastatic disease. However, she underwent a sentinel lymph node biopsy which was also negative. Thus, the diagnosis was finalized as Stage I (T1 N0 M0) MCC. There are only two reported cases in literature about the significant progression of Merkel cell carcinoma in patients who coincidentally were receiving rituximab as a part of treatment for another disease. This raises questions for future investigation and research on whether there is a direct association between rituximab use specifically and the rapid growth of MCC.

A Primary Extracutaneous Presentation of Merkel Cell Carcinoma

Merkel cell carcinoma (MCC) is a rare aggressive cutaneous neuroendocrine malignancy with a mortality rate of around 33%. The presence of advanced disease at the time of diagnosis is associated with poor prognosis. Twofold etiologies have been described in the pathogenesis of Merkel cell carcinoma: chronic exposure to ultraviolet (UV) light and Merkel cell polyomavirus (MCPvY). MCC usually affects sun-exposed skin areas, and the presence of cutaneous nodules is the hallmark of the disease. However, there have been case reports in the literature where the diagnosis of MCC was made in the absence of any cutaneous findings. We present a case report of Merkel cell carcinoma that is unique in its presentation because of the presence of pulmonary and hepatic nodules and the absence of cutaneous lesions.

Application of immune enhanced organoids in modeling personalized Merkel cell carcinoma research

Merkel cell carcinoma (MCC) is a rare neuroendocrine cutaneous cancer, with incidence of less than 1/100,000, low survival rates and variable response to chemotherapy or immunotherapy. Herein we explore the application of patient tumor organoids (PTOs) in modeling personalized research in this rare malignancy. Unsorted and non-expanded MCC tumor cells were isolated from surgical specimens and suspended in an ECM based hydrogel, along with patient matched blood and lymph node tissue to generate immune enhanced organoids (iPTOs). Organoids were treated with chemotherapy or immunotherapy agents and efficacy was determined by post-treatment viability. Nine specimens from seven patients were recruited from December 2018-January 2022. Establishment rate was 88.8% (8/9) for PTOs and 77.8% (7/9) for iPTOs. Histology on matched patient tissues and PTOs demonstrated expression of MCC markers. Chemotherapy response was exhibited in 4/6 (66.6%) specimens with cisplatin and doxorubicin as the most effective agents (4/6 PTO sets) while immunotherapy was not effective in tested iPTO sets. Four specimens from two patients demonstrated resistance to pembrolizumab, correlating with the corresponding patient's treatment response. Routine establishment and immune enhancement of MCC PTOs is feasible directly from resected surgical specimens allowing for personalized research and exploration of treatment regimens in the preclinical setting.

CK20/CK7 Double Negative Merkel Cell Carcinoma In-Situ: A Case Report

An 83-year-old male with a history of both melanoma and non-melanoma skin cancers presented with a light pink non-ulcerated slightly raised 0.6 x 0.5 cm papule on his left lower extremity. Biopsy revealed a proliferation of intraepidermal round blue cells. On immunohistochemical staining, CD56, chromogranin, and pancytokeratin were faintly positive within the lesional population, while synaptophysin was strongly positive. CD45, CK5/6, CK7, CK20, Melan-A, SOX10, and TTF-1 stains were negative. There was no dermal component identified. A Merkel cell polyomavirus (MCPyV) stain was negative. Distant metastases and other in situ pathologies were excluded and a diagnosis of Merkel cell carcinoma in situ (MMCIS) was made. The majority of MCCIS lesions reported in the literature have been discovered amongst other non-melanoma neoplasms. Our findings of a MCCIS with purely intraepidermal involvements without the association with another squamous cell neoplasm is a rare finding. This article is protected by copyright. All rights reserved.

Merkel Cell Polyomavirus: Oncogenesis in a Stable Genome

Merkel cell polyomavirus (MCV) is the causative agent for the majority of Merkel cell carcinoma (MCC) cases. Polyomavirus-associated MCC (MCCP) is characterized by the integration of MCV DNA into the tumor genome and a low tumor mutational burden. In contrast, nonviral MCC (MCCN) is characterized by a high tumor mutational burden induced by UV damage. Since the discovery of MCV, much work in the field has focused on understanding the molecular mechanisms of oncogenesis driven by the MCV tumor (T) antigens. Here, we review our current understanding of how the activities of large T (LT) and small T (ST) promote MCC oncogenesis in the absence of genomic instability. We highlight how both LT and ST inhibit tumor suppressors to evade growth suppression, an important cancer hallmark. We discuss ST interactions with cellular proteins, with an emphasis on those that contribute to sustaining proliferative signaling. Finally, we examine active areas of research into open questions in the field, including the origin of MCC and mechanisms of viral integration.

Merkel Cell Carcinoma: From Pathobiology to Clinical Management

Simple Summary

Merkel cell carcinoma (MCC) is an uncommon type of skin cancer that carries a poor prognosis. It is seen predominantly in old age in sun-exposed body parts. Racial and geographical differences are seen in its occurrence. Viral infection and radiation exposure are the two leading factors implicated in its causation. Small, firm to hard nodule (usually in sun-exposed areas), red with a history of a rapid increase in size is a common personation of the disease. Other body parts such as upper limbs, trunk, and even lower limbs may be also involved. The disease is diagnosed by taking a tissue sample (biopsy) for examination, and other radiological investigations are needed to reach a proper diagnosis with the staging of the disease. There are various treatment options including surgery, radiotherapy, and chemotherapy. Surgery is the primary treatment option though some patients may not be the candidates for operation where other treatment options come into play.

Abstract

Merkel cell carcinoma (MCC) is an infrequent, rapidly growing skin neoplasm that carries a greater probability of regional lymph node involvement, and a grim prognosis in advanced cases. While it is seen predominantly in old age in sun-exposed body parts, the prevalence varies among different races and geographical regions. Merkel cell polyomavirus and UV radiation-induced mutations contribute to its etiopathogenesis. The clinical presentation of MCC lacks pathognomonic features and is rarely considered highly at the time of presentation. Histopathological examination frequently reveals hyperchromatic nuclei with high mitotic activity, but immunohistochemistry is required to confirm the diagnosis. Sentinel lymph node biopsy (SLNB) and imaging are advised for effective staging of the disease. Multimodal management including surgery, radiation therapy, and/or immunotherapy are deployed. Traditional cytotoxic chemotherapies may result in an initial response, but do not result in a significant survival benefit. Checkpoint inhibitors have dramatically improved the prognosis of patients with metastatic MCC, and are recommended first-line in advanced cases. There is a need for well-tolerated agents with good safety profiles in patients who have failed immunotherapies.

Multimodal Strategy in Localized Merkel Cell Carcinoma: Where Are We and Where Are We Heading?

Merkel cell carcinoma (MCC) is an aggressive neuroendocrine tumor of the skin whose incidence is rising. Multimodal treatment is crucial in the non-metastatic, potentially curable setting. However, the optimal management of patients with non-metastatic MCC is still unclear. In addition, novel insights into tumor biology and newly developed treatments (e.g., immune checkpoint inhibitors) that dramatically improved outcomes in the advanced setting are being investigated in earlier stages with promising results. Nevertheless, the combination of new strategies with consolidated ones needs to be clarified. We reviewed available evidence supporting the current treatment recommendations of localized MCC with a focus on potentially ground-breaking future strategies. Advantages and disadvantages of the different treatment modalities, including surgery, radiotherapy, chemotherapy, and immunotherapy in the non-metastatic setting, are analyzed, as well as those of different treatment modalities (adjuvant as opposed to neoadjuvant). Lastly, we provide an outlook of remarkable ongoing studies and of promising agents and strategies in the treatment of patients with non-metastatic MCC.

Merkel Cell Carcinoma

Merkel cell carcinoma (MCC) is a rare and extremely aggressive neuroendocrine carcinoma of the skin, with increasing incidence worldwide. This review intends to propose a comprehensive evaluation of MCC epidemiology, clinical features, pathogenetic mechanisms, diagnosis, and therapies. A section is dedicated to immunological aspects and another to the involvement of angiogenesis and angiogenic growth factors in MCC progression, proposing novel diagnostic and therapeutic approaches. Advanced MCC tumors have been treated with immune checkpoint inhibitors with effective results. Therefore, the state of art of this immunotherapy is also examined, reporting on the most recent clinical trials in the field. We conclude by underlining the achievements in the understanding of MCC pathology and indicating the present needs for effective diagnosis and therapeutic management of the disease.

Merkel Cell Carcinoma from Molecular Pathology to Novel Therapies

Merkel cell carcinoma (MCC) is an uncommon and highly aggressive skin cancer. It develops mostly within chronically sun-exposed areas of the skin. MCPyV is detected in 60-80% of MCC cases as integrated within the genome and is considered a major risk factor for MCC. Viral negative MCCs have a high mutation burden with a UV damage signature. Aberrations occur in RB1, TP53, and NOTCH genes as well as in the PI3K-AKT-mTOR pathway. MCC is highly immunogenic, but MCC cells are known to evade the host's immune response. Despite the characteristic immunohistological profile of MCC, the diagnosis is challenging, and it should be confirmed by an experienced pathologist. Sentinel lymph node biopsy is considered the most reliable staging tool to identify subclinical nodal disease. Subclinical node metastases are present in about 30-50% of patients with primary MCC. The basis of MCC treatment is surgical excision. MCC is highly radiosensitive. It becomes chemoresistant within a few months. MCC is prone to recurrence. The outcomes in patients with metastatic disease are poor, with a historical 5-year survival of 13.5%. The median progression-free survival is 3-5 months, and the median overall survival is ten months. Currently, immunotherapy has become a standard of care first-line therapy for advanced MCC.

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.

Merkel cell carcinoma: A systematic review of the demographic and clinical characteristics of 847 cases in Japan

Merkel cell carcinoma (MCC) is a rare but aggressive neuroendocrine carcinoma of the skin associated with Merkel cell polyomavirus and immunosuppression. Although MCC incidence is rising worldwide, MCC has not been sufficiently investigated in Japan. This study aimed to determine MCC demographics in Japan, including incidence, age, sex, location, spontaneous regression, and pure/combined MCC. Using PubMed and Igaku Chuo Zasshi, 847 MCC cases between 1985 and 2015 were extracted, and the main epidemiological characteristics were described. The mean age of all patients was 77.5 years. Regarding the characterized lesions, 63.0% were located on the head and neck, 5.2% on the trunk, 12.6% on the upper limb, 15.1% on the lower limb, 3.5% on the buttocks, and 0.6% on the genitals. Histopathological information regarding the presence of other malignancies could be retrieved in 611 cases, and a coexisting malignancy, mainly squamous cell carcinoma and Bowen's disease, was present in 14.2%. Subcutaneous MCC was observed in 31 patients with a male : female ratio of 1.07 (16 men/15 women). Nodal lesions with unknown primary tumor location were described in 19 patients with a male : female ratio of 0.9 (nine men/10 women) and a mean age of 77.7 years. Of 640 evaluable cases, spontaneous regression developed in 9.1%. Among those 58 patients, the male : female ratio was 1:2.1 in 56 evaluable cases (18 men/38 women). Merkel cell polyomavirus was assessed in 180 patients, and the virus was detected in 31.1% and not detected in 68.9% of the patients. MCC is a rare disease in Japan, with incidence rates and male : female ratios differing from those in the USA and European countries. Besides, this study reveals the high frequency of subcutaneous MCC and MCC with divergent differentiation patterns and spontaneous regression in Japan compared to other countries.

Merkel cell carcinoma: A review

Merkel cell carcinoma has been a focus of active scientific investigation in recent years and new information on the topic has emerged. Although uncommon, this primary cutaneous neuroendocrine carcinoma, usually involving the head/neck of elderly individuals, has a poor prognosis. Within the past two decades, an increase in the incidence of the tumor and the discovery of its link to the Merkel cell polyomavirus have focused medical attention on the lesion. The resulting studies have improved our understanding of the biology of the neoplasm and contributed to clinical care. Specifically, two pathogenic subsets of the tumor have come to light, the majority due to Merkel cell polyomavirus and the minority caused by ultraviolet radiation-induced genetic damage. This dichotomy carries prognostic implications favoring the former subset. In addition, having capitalized on the known susceptibility of the tumor to immune influences, investigators have recently discovered its responsiveness to immune checkpoint inhibition. This revelation has constituted a therapeutic milestone at the clinical level. Herein we provide an overview of the topic, outline updates in the field and place an emphasis on dermatopathologic aspects of Merkel cell carcinoma.

Recent Therapeutic Advances and Change in Treatment Paradigm of Patients with Merkel Cell Carcinoma

Merkel cell carcinoma (MCC) is a rare, aggressive, primary cutaneous neuroendocrine tumor that typically presents as an indurated nodule on sun-exposed areas of the head and neck in the white population. Major risk factors include immunosuppression, UV light exposure, and advanced age. Up to 80% of MCC are associated with Merkel cell polyomavirus. About 50% of patients present with localized disease, and surgical resection with or without adjuvant radiotherapy is generally indicated in this context. However, recurrence rates are high and overall prognosis rather poor, with mortality rates of 33%-46%. MCC is a chemosensitive disease, but responses in the advanced setting are seldom durable and not clearly associated with improved survival. Several recent trials with checkpoint inhibitors (pembrolizumab, avelumab, nivolumab) have shown very promising results with a favorable safety profile, in both chemonaïve and pretreated patients. In 2017, avelumab was approved by several regulatory agencies for the treatment of metastatic MCC, the first drug to be approved for this orphan disease. More recently, pembrolizumab has also been approved by the U.S. Food and Drug Administration in this setting. Immunotherapy has therefore become the new standard of care in advanced MCC. This article reviews current evidence and recommendations for the diagnosis and treatment of MCC and discusses recent therapeutic advances and their implications for care in patients with advanced disease. This consensus statement is the result of a collaboration between the Spanish Cooperative Group for Neuroendocrine Tumors, the Spanish Group of Treatment on Head and Neck Tumors, and the Spanish Melanoma Group. IMPLICATIONS FOR PRACTICE: Merkel cell carcinoma (MCC) is an uncommon aggressive skin cancer associated with advanced age, UV light exposure, and immunosuppression. Up to 80% are associated with Merkel cell polyomavirus. MCC is a chemosensitive disease, but tumor responses in the advanced setting are short-lived with no long-term survivors. Recent clinical trials with immune checkpoint inhibitors (i.e., pembrolizumab, avelumab, nivolumab) have shown promising results, with avelumab becoming the first drug to receive regulatory approval for this orphan indication. Further follow-up is needed, however, to define more adequately the long-term benefits of these drugs, and continued research is warranted to optimize immunotherapeutic strategies in this setting.

Human oncoviruses: Mucocutaneous manifestations, pathogenesis, therapeutics, and prevention: Papillomaviruses and Merkel cell polyomavirus

In 1964, the first human oncovirus, Epstein-Barr virus, was identified in Burkitt lymphoma cells. Since then, 6 other human oncoviruses have been identified: human papillomavirus, Merkel cell polyomavirus, hepatitis B and C viruses, human T-cell lymphotropic virus-1, and human herpesvirus-8. These viruses are causally linked to 12% of all cancers, many of which have mucocutaneous manifestations. In addition, oncoviruses are associated with multiple benign mucocutaneous diseases. Research regarding the pathogenic mechanisms of oncoviruses and virus-specific treatment and prevention is rapidly evolving. Preventative vaccines for human papillomavirus and hepatitis B virus are already available. This review discusses the mucocutaneous manifestations, pathogenesis, diagnosis, treatment, and prevention of oncovirus-related diseases. The first article in this continuing medical education series focuses on diseases associated with human papillomavirus and Merkel cell polyomavirus, while the second article in the series focuses on diseases associated with hepatitis B and C viruses, human T-cell lymphotropic virus-1, human herpesvirus-8, and Epstein-Barr virus.

A novel report of a primary Merkel cell carcinoma lesion in the nasal vestibule

Merkel cell carcinoma (MCC) accounts for less than 1% of cutaneous malignancies. As the lesion may mimic benign entities, clinicians' differential should include rare entities to improve outcomes by early intervention. We present a case of primary MCC in the nasal vestibule requiring partial rhinectomy, suprahyoid lymphadenectomy, and radiation therapy.

The Use of BEREP4 Immunohistochemistry Staining for Detection of Basal Cell Carcinoma

Basal Cell Carcinoma (BCC) is the most common type of malignant cancer found in the world today with a 3–10% increase in incidence each year. The American Cancer Society reported that 8 out of 10 patients with skin cancer are suffering from BCC with over 2 million new cases each year. BCC needs to be detected at the early stages to prevent local destruction causing disabilities to patients and increasing treatment costs. Furthermore, BCC patients who have undergone surgery are still at risk for recurrence, especially when the surgery performed fails to remove all the BCC cells, even when conventional histopathological testing after surgery has reported a surgically free margin. This review aims to evaluate studies on the use of BerEP4 immunohistochemistry staining on pathological sections of various types of BCC as well as its shortfalls. BerEP4 is a monoclonal antibody which detects specific epithelial-glycoprotein-adhesion-molecules (EpCAM) found on BCC cells. Various studies have shown that BerEP4 has a high sensitivity and specificity in detecting only BCC cells. The use of BerEP4 immunohistochemistry testing for the routine examination of cases of BCC is expected to be able to increase and improve early diagnosis as well as prevent recurrence after surgery.

Insulinoma-associated 1: A novel nuclear marker in Merkel cell carcinoma (cutaneous neuroendocrine carcinoma)

Merkel cell carcinoma (MCC) is a rare, clinically aggressive, cutaneous neuroendocrine (NE) neoplasm. As a tumor with small, round, blue cells, the histologic differential diagnosis for MCC can include melanoma, metastatic small cell carcinoma (SCC), nodular hematopoietic tumors, basal cell carcinoma (BCC), atypical variants of squamous carcinoma and the uncommon occurrence of primary cutaneous Ewing sarcoma. In cases with atypical histology or without the classic immunophenotype, the diagnosis can be challenging. Ultimately, immunohistochemistry (IHC) is essential to the definitive diagnosis of MCC and in difficult cases, the diagnosis may hinge entirely on the immunophenotype of the tumor cells. Insulinoma-associated 1 (INSM1) is a transcription factor expressed in tissues undergoing terminal NE differentiation. As a nuclear protein tied to both differentiation and the cell cycle, INSM1 may offer additional utility in comparison to traditional, cytoplasmic markers of NE differentiation.

Merkel Cell Carcinoma in a Steer

Merkel cell carcinoma is a rare and aggressive cutaneous neuroendocrine tumour reported only in man, dogs and cats. A 20-month-old Japanese black fattening steer was presented with necrotic protruding skin masses over the left thoracic area and a 20 × 25 cm subcutaneous mass in the left abdominal area. Microscopical evaluation of the masses revealed cords of small to medium-sized round tumour cells with marked anisocytosis and anisokaryosis and clear and vacuolated cytoplasm, which were separated by a delicate fibrovascular stroma and arranged in a trabecular and nested pattern. Necropsy examination revealed multiple solid white nodular masses in the lungs. Immunohistochemistry (IHC) for cytokeratin (CK) 20 and CKAE1/3 revealed focal perinuclear labelling of tumour cells. IHC for the neuroendocrine markers chromogranin A and neuron specific enolase, the neuroepithelial stem cell marker nestin and the hormonal markers adrenocorticotropic hormone and calcitonin revealed diffuse cytoplasmic labelling of all tumour cells. Ultrastructurally, the tumour cells contained few neurosecretory granules and abundant glycogen pools. The tumours were diagnosed as Merkel cell carcinoma with pulmonary metastases and this case represents the first such diagnosis in cattle.

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.

[Care of Merkel cell carcinoma and role of the radiotherapy]

Merkel cell carcinoma is a rare neuro-endocrine tumor of skin with a poor prognosis. Data available in literature are scarce. Current treatment for locoregional disease is based on combined treatment by surgery and radiotherapy. However these treatments are controversial. The aim of the present review is to sum up the different available studies and to compare national and international guidelines.

Sigmoid colonic metastasis by lymphatic spread occurring with unilateral Krukenberg tumor considered to be caused by stage IA early gastric cancer: A case report

Gastric cancer is one of the most common malignancies in Asia, and the second most common cause of cancer-associated mortality in Japan. Colorectal metastases originating from gastric adenocarcinoma are extremely rare. The present study reports an unusual case of lymphogenous sigmoid metastasis of gastric adenocarcinoma occurring in a 58-year-old female patient. Endoscopic and radiological findings were indicative of 0-IIc+IIa early gastric cancer, and radical distal gastrectomy with D2 lymph node dissection was performed. The pathological diagnosis was stage IA gastric adenocarcinoma (T1bN0M0), according to the Japanese classification of gastric cancer. A follow-up examination at 18 months post surgery revealed a recurrence of paraaortic lymph node metastasis, detected by abdominal computed tomography (CT) and positron emission tomography (PET)/CT. The patient received chemotherapy with S-1 and cisplatin. Subsequently, radiotherapy was administered to the paraaortic lymph nodes at levels Th11-L3. Follow-up abdominal CT and PET/CT revealed an enlarged left ovary, and abnormal uptake in the left ovary and sigmoid colon. An oophorectomy and sigmoidectomy with D3 lymph node dissection were performed. The pathological diagnosis was metastatic adenocarcinoma; this was identical to the gastric pathology in the previous pathological report. The patient continued treatment with chemotherapy. Although sigmoid colonic metastasis from gastric cancer is extremely rare, metastasis from gastric cancer must be considered during the differential diagnosis of cases involving a colorectal mass and a previous history of gastric cancer.

Merkel cell carcinoma of the abdominal wall

Merkel cell carcinoma also known as neuroendocrine carcinoma of the skin is a very rare skin tumor. It commonly presents in the old age and the common sites are head, neck and extremities. The diagnosis requires histopathological examination with immunohistochemical correlation. We report a case of Merkel cell carcinoma stage IIIB with bilateral inguinal lymphadenopathy that on FNAB showed metastatic deposits of the tumor.

Nuclear medicine techniques in Merkel cell carcinoma: A case report and review of the literature

Merkel cell carcinoma (MCC) is a rare and aggressive type of neuroendocrine cancer of the skin. It predominantly affects the elderly, with a predilection for the sun-exposed skin of the head and neck. Risk factors include immune-suppressing diseases, such as human immunodeficiency virus (HIV), chronic lymphocytic leukemia and multiple myeloma, organ transplantation, and the presence of the newly-identified Merkel cell polyomavirus (MCPyV). Diagnosis is based on pathological findings, primarily the immunohistochemical determination of cytokeratin 20 positivity. By contrast, staging relies on conventional imaging methods, such as ultrasonography, computed tomography (CT) and magnetic resonance imaging, and nuclear medicine techniques, such as sentinel lymph node scintigraphy, somatostatin receptor scintigraphy (SRS), and positron emission tomography (PET)/CT with ¹⁸F-fluorodeoxyglucose (FDG) or alternative radiopharmaceuticals. The treatment of MCC is primarily surgical, with possible adjuvant radiation, while the use of chemotherapy appears to be an alternative therapeutic option that is used only in specific cases. The present study describes the case of a 43-year-old HIV-positive Caucasian man with MCC located on the posterior surface of the left thigh, which was identified by cytological and histological examination of tissue sampled by fine needle aspiration and biopsy performed under CT. SRS demonstrated a high uptake of ¹¹¹In-diethylene triamine pentaacetic acid-octreotide at the affected site. Therefore, the lesion was surgically excised, and the patient received chemotherapy and adjuvant radiotherapy. Three months subsequent to treatment, the patient underwent a PET/CT scan with ¹⁸F-FDG that demonstrated uptake in the cervical lymph nodes and the area of the excised lesion. These findings indicated that the disease was in remission. The aim of the present study was to highlight the value and contribution of nuclear medicine in the diagnosis, staging and follow-up, using PET/CT, octreoscan and sentinel lymph node scintigraphy, of patients with MCC, as well as the therapeutic strategy of radiolabelled somatostatin analogue scintigraphy.

Focus on Merkel cell carcinoma: diagnosis and staging

Merkel cell carcinoma is a rare lymphophilic skin tumor of neuroendocrine origin with the potential for rapid progression. Small, localized lesions are diagnosed and treated clinically, but advanced tumors often undergo imaging evaluation. Due to its rarity, radiologists are unaware of evocative imaging features and usually do not consider Merkel cell carcinoma in the differential diagnosis of soft tissue tumors. Appropriate staging is important to determine appropriate treatment and has an impact on patient prognosis. Multimodality imaging is usually needed, and there is no consensus on the optimal imaging strategy. The purpose of this article is to review various aspects of Merkel cell carcinoma imaging and look in detail at how optimal multimodality staging should be carried out.

Merkel cell polyomavirus infection in a patient with merkel cell carcinoma: a case report

Introduction:

Merkel cell carcinoma (MCC) is a rare and highly aggressive malignancy of the skin which occurs mainly in old people and is very uncommon in young individuals. A new tumor virus belonging to the Polyomaviridae family; Merkel Cell Polyomavirus (MCPyV) has recently been identified in more than 80% of MCCs.

Case Presentation:

We conducted a retrospective review on the archives of the Department of Pathology; Imam Khomeini Hospital Cancer Institute affiliated to Tehran University of Medical Sciences to confirm the MCC samples and we found medical records and samples of a young case with MCC who developed leg skin and scalp tumor six and seven years after bone marrow transplantation, respectively. We analyzed patient formalin-fixed paraffin-embedded samples for the presence of MCPyV DNA using polymerase chain reaction (PCR) method, and the PCR amplicons were subjected to DNA sequencing. Merkel Cell Polyomavirus DNA was detected in both tumors from patient and sequence analysis of the viral LT3 region showed a close homology to strains circulating worldwide.

Conclusions:

The findings of this study are consistent with the hypothesis that local, systemic, or tumor-induced immunosuppression may allow the MCPyV to initiate skin aggressive cancer. It is necessary to maintain regular check over patients taking immunosuppressive medications for MCPyV infection. Since there is not any information about detection and molecular biology analysis of MCPyV among Iranian patients with MCC, this study provides more information about MCC and MCPyV in Iran.

Merkel cell polyomavirus small T antigen is oncogenic in transgenic mice

Merkel cell carcinoma (MCC) is a rare and deadly neuroendocrine skin tumor frequently associated with clonal integration of a polyomavirus, MCPyV, and MCC tumor cells express putative polyomavirus oncoproteins small T antigen (sTAg) and truncated large T antigen (tLTAg). Here, we show robust transforming activity of sTAg in vivo in a panel of transgenic mouse models. Epithelia of pre-term sTAg-expressing embryos exhibited hyperplasia, impaired differentiation, increased proliferation and apoptosis, and activation of a DNA damage response. Epithelial transformation did not require sTAg interaction with the PP2A protein complex, a tumor suppressor in some other polyomavirus transformation models, but was strictly dependent on a recently-described sTAg domain that binds Fbxw7, the substrate-binding component of the SCF ubiquitin ligase complex. Postnatal induction of sTAg using a Cre-inducible transgene also led to epithelial transformation with development of lesions resembling squamous cell carcinoma in situ and elevated expression of Fbxw7 target proteins. Our data establish that expression of MCPyV sTAg alone is sufficient for rapid neoplastic transformation in vivo, implicating sTAg as an oncogenic driver in MCC and perhaps other human malignancies. Moreover, the loss of transforming activity following mutation of the sTAg Fbxw7 binding domain identifies this domain as crucial for in vivo transformation.

Merkel cell carcinoma with partial B-cell blastic immunophenotype: a potential mimic of cutaneous richter transformation in a patient with chronic lymphocytic lymphoma

Merkel cell polyomavirus (MCPyV) is a DNA virus whose pathogenic mechanisms in Merkel cell carcinoma (MCC) are still being unraveled. Emerging reports of an association between MCPyV and chronic lymphocytic lymphoma (CLL) have begun to broaden our understanding of the oncogenic mechanisms of this virus and the known association between these 2 malignancies. Herein, we report a case of MCC demonstrating a B-cell immunophenotype arising in a patient with CLL being treated with rituximab. In this context, we discuss the differential diagnostic considerations, especially with cutaneous Richter transformation (diffuse large B-cell lymphoma). We also assessed for the presence of MCPyV in both the patient's MCC and the CLL. Finally, we provide a large meta-analysis of patients with CLL and MCC. Patients with both MCC and CLL have a dismal prognosis, with greater than 50% overall mortality within the first year and a half after MCC diagnosis.

Metastatic Merkel cell carcinoma (MCC) of pancreas and breast: a unique case

Merkel cell carcinoma (MCC) is a rare potentially fatal skin tumor affecting older and immunosuppressed individuals. It is highly malignant with high rates of metastasis and poor survival.

We present a case of a 67-year-old woman with a palpable mass in the upper abdomen. An abdominal CT revealed a mass in the tail of the pancreas. Two weeks before, lumpectomy of a 3.5 cm tumor of the left breast had been performed. Histology showed a primary neuroendocrine carcinoma of the mammary gland. The patient’s medical history was significant for a 0.7 × 0.9 cm MCC removed from her left forearm 2.5 years ago. There was no evidence of vascular involvement or peritoneal disease and by all criteria was resectable. A somatostatin receptor scintigraphy showed an enhanced uptake in the pancreatic tail region. The tumor was immunohistochemically strong staining for synaptophysin and CD56. The diagnosis of a metastatic-MCC in the tail of the pancreas was made. Further histological investigation of the prior removed neuroendocrine breast tumor and the MCC of the left forearm confirmed neuroendocrine origin and identical histology to the previously resected MCC of the left forearm. In this article, we aim to highlight that MCC has the potential to spread even in unusual organs, such as pancreas or breast, and therefore a diligent follow-up should be applied in patients with MCC.

Merkel cell carcinoma: the past, the present, and the future

Since the first description of the Merkel cell carcinoma by Cyril Toker in 1972, the number of studies has significantly increased over the last 4 decades. In this review, we will illustrate the historical background of the Merkel cell carcinoma beginning with the 19th century, the first description of the Merkel cell to the finding of the CK20 as a highly specific diagnostic marker and finally to the recently detected Merkel cell polyomavirus (MCPyV). Moreover, we will highlight the beginning of adjuvant therapeutic regimens with radiotherapy and chemotherapy and discuss the diagnostic work-up including imaging and histology of patients with Merkel cell carcinoma. Another very rapidly growing and interesting field of research is the development of patients' specific and tailored targeted therapy, in particular in patients with distant metastatic disease.

Merkel cell carcinoma of the head and neck: a single institutional experience

Merkel cell carcinoma (MCC) is a rare cutaneous malignancy occurring mostly in older immunocompromized Caucasian males. A growing incidence of MCC has been reported in epidemiological studies. Treatment of MCC usually consists of surgical excision, pathological lymph node evaluation, and adjuvant radiotherapy. This paper reports the experience of a single tertiary center institution with 17 head and neck Merkel cell carcinoma patients. Median followup for the cohort was 37.5 months. After five years, recurrence-free survival, disease specific survival, and overall survival were 85%, 90%, and 83%, respectively. Our limited data support the use of adjuvant radiotherapy. We also report two cases of MCC located at the vestibule of the nose and two cases of spontaneous regression after diagnostic biopsy. About 40% of our patients were referred to our center for surgical revision and pathological lymph node evaluation. Increased awareness of MCC and an interdisciplinary approach are essential in the management of MCC.