Merkel Cell Carcinoma

Merkel cell carcinoma: updates in tumor biology, emerging therapies, and preclinical models

Merkel cell carcinoma (MCC) is an aggressive cutaneous neuroendocrine carcinoma thought to arise via either viral (Merkel cell polyomavirus) or ultraviolet-associated pathways. Surgery and radiotherapy have historically been mainstays of management, and immunotherapy has improved outcomes for advanced disease. However, there remains a lack of effective therapy for those patients who fail to respond to these established approaches, underscoring a critical need to better understand MCC biology for more effective prognosis and treatment. Here, we review the fundamental aspects of MCC biology and the recent advances which have had profound impact on management. The first genetically-engineered mouse models for MCC tumorigenesis provide opportunities to understand the potential MCC cell of origin and may prove useful for preclinical investigation of novel therapeutics. The MCC cell of origin debate has also been advanced by recent observations of MCC arising in association with a clonally related hair follicle tumor or squamous cell carcinoma in situ. These studies also suggested a role for epigenetics in the origin of MCC, highlighting a potential utility for this therapeutic avenue in MCC. These and other therapeutic targets form the basis for a wealth of ongoing clinical trials to improve MCC management. Here, we review these recent advances in the context of the existing literature and implications for future investigations.

Surgical Management of Patients with Parotid Involvement from Non-Melanoma Skin Cancer of the Head and Neck

We conducted a retrospective, longitudinal study on a single-center series of patients who underwent parotidectomy in the management of advanced head and neck non-melanoma skin cancer (hnNMSC). The aim of this study was to identify prognostic factors associated with worse outcomes. Forty-one men and nine women were included. The mean age at the time of surgery was 78.9 years. The 5-year overall survival, disease-specific survival, locoregional recurrence-free survival, and distant metastasis-free survival calculated with Kaplan-Meier curves were 39.9%, 56.3%, 58.6%, and 82.1%, respectively. A univariate analysis showed that the status of the margins, facial nerve direct involvement, lymph vascular invasion, and histological grading were associated with worse outcomes (p < 0.05). Positive margins were associated with worse disease-specific survival also in a multivariate analysis (p = 0.001, HR = 32.02, and CIs 4.338 to 351.3). Because the resection in free margins is the most important prognostic factor, early diagnosis or, in the case of advanced disease, extensive surgical resection with concomitant reconstruction is needed. Adjuvant therapy is indicated in selected cases.

Rare but Still There: An Interesting Case of Cytokeratin 20-Negative Merkel Cell Carcinoma

Merkel cell carcinoma (MCC) of the skin is a rare and aggressive primary neuroendocrine tumor that mainly involves sun-exposed areas and can metastasize to other parts of the body. Due to varied clinical features and the sharing of similar histological features with other neuroendocrine tumors, diagnosis can be challenging. Therefore, immunohistochemistry plays an important role in diagnosis, and the characteristic perinuclear staining with cytokeratin 20 (CK 20) helps to differentiate it from other morphologically similar tumors, especially metastatic small cell carcinoma of the lung. We describe an interesting case of a 78-year-old female who was referred by a general practitioner (GP) with a few months' history of asymptomatic, rapidly enlarging, erythematous, nodular lesion on her left upper arm. Due to clinical findings and the location of the lesion on the sun-exposed area, wide differential diagnoses were considered. The lesion was excised for histological diagnosis. Surprisingly, morphological features favour the diagnosis of a neuroendocrine tumor. However, histological features including immunohistochemistry rendered it difficult to differentiate between primary cutaneous neuroendocrine carcinoma (Merkel cell CA) and metastatic small cell carcinoma of the lung due to the lack of specific and sensitive marker of CK 20 on immunohistochemistry. Subsequently, the patient had computer tomography of the chest/abdomen and pelvis (CTTAP) and positron emission tomography (PET) scans to rule out underlying primary malignancy. The case was also discussed at local and specialist skin multidisciplinary team meetings (MDT) including neuroendocrine MDT and a consensus diagnosis of Merkel cell carcinoma of the skin with negative CK 20 was established.

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.

Merkel Cell Carcinoma: An Otolaryngological Point of View of An Unusual Sinonasal Mass

Merkel cell carcinoma is a pathologic diagnosis mainly observed in sun-exposed cutaneous areas, like the head and neck. Ultraviolet (UV) exposure and immunosuppression are the common predisposing factors. Merkel cell carcinoma of the head and neck is quite an uncommon disease. This case report involves a 56-year-old man who exhibited a skin lesion on the nasal dorsum with a mass in the right maxillary sinus. The biopsies from both sides were diagnostic for Merkel cell carcinoma. The patient underwent endoscopic sinus surgery and removal of the skin lesion with free margins. The patient has been free of disease for the last 20 months now and maintains follow-up with endoscopy and imaging in the Ear Nose Throat office. Only a few cases of Merkel cell carcinoma of the nasal mucosa have been reported in the literature. We report our approach and management of this rare pathologic presentation.

Defining the Profile of Patients with Primary Merkel Cell Carcinoma in Central Italy: A Retrospective Analysis

Simple Summary

Merkel cell carcinoma is rarely suspected and often misdiagnosed in the clinical setting. Robust epidemiological data are missing, contributing to a lack of knowledge of this type of tumor among clinicians. We aimed to demographically and clinically characterize Merkel cell carcinoma patients and the tumor’s features through a multicenter real-world analysis of patients from Central Italy from 2015 to 2020. Our study revealed a higher incidence rate compared to the one estimated for the Italian population, with the lower limbs as the anatomical site affected the most. We also report that several specialists are involved in the first-line management of the pathology. In this light, a deeper knowledge of this tumor is advised.

Abstract

Merkel cell carcinoma (MCC) is a rare neuroendocrine skin cancer that usually occurs in elderly people on sun-exposed areas, with a predisposition to local recurrence. Evidence suggests a growing incidence over the past decade; however, robust epidemiologic data are still lacking. We describe the MCC population in clinical practice in a retrospective analysis of demographic, clinical, and tumor characteristics from medical records of primary MCC patients, between 2015 and 2020, at six dermatology clinics in Central Italy. Ninety-four patients were included (57.4% male; mean age 78.2 ± 10.1 years, range 47–99 years). The estimated incidence rate of MCC was 0.93 per 100,000 inhabitants/year. Lower limbs were the most frequently affected site (31.5%), and 54% of patients for whom information was available were immunosuppressed. Lymph node involvement was reported in 42.5% of patients, and distant metastases in almost 20%. Most patients underwent surgery for tumor excision and were mainly referred to specialized dermatology clinics by dermatologists (47.9%) and general surgeons (28.7%). Apart from the relatively balanced prevalence of MCC in men and women, the predominant location on lower limbs, and the higher incidence rate compared with previous reports in Italy, this population is, overall, similar to the populations described in other observational studies. MCC management requires the involvement of several specialties. Increased awareness of MCC and standardization of its management are urgently needed.

The Role of Citrate Homeostasis in Merkel Cell Carcinoma Pathogenesis

Simple Summary

Merkel cell carcinoma (MCC) is a rare but highly aggressive skin cancer. Despite important progress, overall understanding of the events that drive MCC carcinogenesis remains incomplete. We discovered that the plasma membrane citrate transporter (pmCiC) is upregulated in Merkel cell carcinoma cell lines. Cancer cells import extracellular citrate via pmCiC to support their metabolism, which is critical to support proliferation and metastatic spread. In this study, we show that inhibition of pmCiC can decrease the growth rate of Merkel cell carcinoma cell lines. Targeting pmCiC and thereby the tumor metabolism should be considered further as a potential anti-cancer therapy.

Abstract

Merkel cell carcinoma (MCC) is a rare but highly aggressive tumor of the skin with a poor prognosis. The factors driving this cancer must be better understood in order to discover novel targets for more effective therapies. In the search for targets, we followed our interest in citrate as a central and critical metabolite linked to fatty acid synthesis in cancer development. A key to citrate uptake in cancer cells is the high expression of the plasma membrane citrate transporter (pmCiC), which is upregulated in the different adenocarcinoma types tested so far. In this study, we show that the pmCiC is also highly expressed in Merkel cell carcinoma cell lines by western blot and human tissues by immunohistochemistry staining. In the presence of extracellular citrate, MCC cells show an increased proliferation rate in vitro; a specific pmCiC inhibitor (Na⁺-gluconate) blocks this citrate-induced proliferation. Furthermore, the 3D in vivo Chick Chorioallantoic Membrane (CAM) model showed that the application of Na⁺-gluconate also decreases Merkel cell carcinoma growth. Based on our results, we conclude that pmCiC and extracellular citrate uptake should be considered further as a potential novel target for the treatment of Merkel cell carcinoma.

Merkel Cell Carcinoma Display PIEZO2 Immunoreactivity

As an essential component of mechano-gated ion channels, critically required for mechanotransduction in mammalian cells, PIEZO2 is known to be characteristically expressed by Merkel cells in human skin. Here, we immunohistochemically investigated the occurrence of Piezo channels in a case series of Merkel cell carcinoma. A panel of antibodies was used to characterize Merkel cells, and to detect PIEZO2 expression. All analyzed tumors displayed PIEZO2 in nearly all cells, showing two patterns of immunostaining: membranous and perinuclear dot-like. PIEZO2 co-localized with cytokeratin 20, chromogranin A, synaptophysin and neurofilament. Moreover, neurofilament immunoreactive structures resembling nerve-Merkel cell contacts were occasionally found. PIEZO2 was also detected in cells of the sweat ducts. The role of PIEZO2 in Merkel cell carcinoma is still unknown, but it could be related with the mechanical regulation of the tumor biology or be a mere vestige of the Merkel cell derivation.

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.

Diagnostic clues for differentiating Merkel cell carcinoma from lymphoma in fine-needle aspiration cytology

Nodal fine needle aspiration (FNA) is usually the first procedure in the work-up of malignancy of unknown primary. Merkel cell carcinoma (MCC) is an aggressive cutaneous cancer more common in Caucasians but rare among Asians. It is a diagnostic challenge in evaluating FNA from a metastatic MCC without the knowledge of a current or prior history of skin cancer. We report the case of a Taiwanese male with cervical and axillary masses. The diagnosis of the FNA from the axillary lymph node was lymphoproliferative lesion suspicious for lymphoma. The histopathological evaluation of nodal biopsy revealed a metastatic neuroendocrine carcinoma and the subsequent excision of the right palm tumor confirmed MCC. Retrospective review of the FNA and imprint cytology smears of the nodal biopsy showed nuclear molding, Indian filing and rare cytoplasmic pale bodies, but no lymphoglandular bodies. Cytologically metastatic MCC may mimic small round cell tumor including lymphoma, we consider these three cytological features as additional diagnostic clues for metastatic MCC. In this report, we present the cytologic and pathological features of this metastatic MCC and discuss the differential diagnosis of the cytologic mimickers.

APOBEC and Cancer Viroimmunotherapy: Thinking the Unthinkable

The apolipoprotein B mRNA editing enzyme catalytic polypeptide (APOBEC) family protects against infection by degrading incoming viral genomes through cytosine deamination. Here, we review how the potential to unleash these potent DNA mutagens comes at a price as APOBEC DNA mutagenesis can contribute to development of multiple types of cancer. In addition, because viral infection induces its expression, APOBEC is seen as the enemy of oncolytic virotherapy through mutation of the viral genome and by generating virotherapy-resistant tumors. Therefore, overall APOBEC in cancer has received very poor press. However, we also speculate how there may be silver linings to the storm clouds (kataegis) associated with APOBEC activity. Thus, although mutagenic genomic chaos promotes emergence of ever more aggressive subclones, it also provides significant opportunity for cytotoxic and immune therapies. In particular, the superpower of cancer immunotherapy derives in part from mutation, wherein generation of tumor neoantigens-neoantigenesis-exposes tumor cells to functional T-cell repertoires, and susceptibility to immune checkpoint blockade. Moreover, APOBECs may be able to induce suprathreshold levels of cellular mutation leading to mitotic catastrophe and direct tumor cell killing. Finally, we discuss the possibility that linking predictable APOBEC-induced mutation with escape from specific frontline therapies could identify mutated molecules/pathways that can be targeted with small molecules and/or immunotherapies in a Trap and Ambush strategy. Together, these considerations lead to the counterintuitive hypothesis that, instead of attempting to expunge and excoriate APOBEC activity in cancer therapy, it might be exploited-and even, counterintuitively, encouraged.

Merkel cell carcinoma

Merkel cell carcinoma (MCC) of the skin is a rare, aggressive form of skin cancer that metastasizes to other parts of the body. This cutaneous neuroendocrine tumour mainly affects older people, with most cases generally occurring over the age of 50 years. Merkel cell polyomavirus has been shown to induce gene mutations resulting in this skin cancer, with immunosuppression and ultraviolet radiation being other key risk factors in its pathogenesis. MCC is clinically seen as a rapidly enlarging, isolated, irregular erythematous nodule typically found on sun-exposed sites. Diagnosis is through clinical examination followed by tissue biopsy, which demonstrates characteristic histopathological neuroendocrine features. Immunohistochemistry plays a crucial role in diagnosis with the characteristic perinuclear staining with cytokeratin-20 helping to differentiate it from other morphologically similar tumours. Sentinel lymph node biopsy and imaging is essential for staging and determining prognosis. Surgical excision is the mainstay of treatment for localized disease although adjuvant radiotherapy is often required. Metastatic disease involves a very poor prognosis, and immune checkpoint inhibitors have recently shown promise in the treatment of metastatic disease. Avelumab, a monoclonal antibody that binds to the programmed death-1 receptor, has been approved by the National Institute for Health and Care Excellence and shown encouraging survival outcomes. It provides an option for treating metastatic carcinoma in adults after they have failed ≥ 1 line of chemotherapy for metastatic disease.

Evaluation of Merkel Cell Polyomavirus DNA in Tissue Samples from Italian Patients with Diagnosis of MCC

Because the incidence of Merkel cell carcinoma (MCC) has increased significantly during the last 10 years and it is recognized that Merkel cell polyomavirus (MCPyV) and ultraviolet (UV) radiation represent two different etiological inputs sharing clinical, histopathological, and prognostic similar features, although with different prognosis, this study investigated the detection of MCPyV in skin and lymph nodes with histological diagnosis of MCC. Formalin-fixed paraffin-embedded tissue (FFPE) were retrieved from archived specimens and MCPyV non-coding control region (NCCR) and viral capsid protein 1 (VP1) sequences were amplified and sequenced. Results provide an interesting observation concerning the discrepancy between the MCPyV DNA status in primary and metastatic sites: in fact, in all cases in which primary and metastatic lesions were investigated, MCPyV DNA was detected only in the primary lesions. Our data further support the “hit-and-run” theory, also proposed by other authors, and may lead to speculation that in some MCCs the virus is only necessary for the process of tumor initiation and that further mutations may render the tumor independent from the virus. Few point mutations were detected in the NCCR and only silent mutations were observed in the VP1 sequence compared to the MCPyV MCC350 isolate. To unequivocally establish a role of MCPyV in malignancies, additional well-controlled investigations are required, and larger cohorts should be examined.

Merkel Cell Carcinoma of the Hand in a Young Patient

Merkle cell carcinoma (MCC) is a rare, malignant neuroendocrine skin cancer that typically affects patients in the seventh decade of life. Reports of MCC affecting young patients are limited, and there are few mentions of the management of these lesions when they present on the hand and fingers. Hand surgeons must be educated regarding the diagnosis of MCC and the multidisciplinary management required to achieve optimal results. We present the case of a 22-year-old woman with MCC arising on the dorsum of the second digit. Treatment with wide local excision, coverage of the resulting soft tissue defect with a reverse second dorsal metacarpal artery flap, and subsequent radiotherapy resulted in no evidence of disease recurrence or metastasis at 1 year. This case highlights the commonly encountered delay in the diagnosis of this lesion and the necessity for a high index of suspicion when evaluating a patient with an enlarging, solitary hand nodule.

Multidisciplinary Treatment, Including Locoregional Chemotherapy, for Merkel-Polyomavirus-Positive Merkel Cell Carcinomas: Perspectives for Patients Exhibiting Oncogenic Alternative Δ exon 6-7 TrkAIII Splicing of Neurotrophin Receptor Tropomyosin-Related Kinase A

Merkel cell carcinomas (MCCs) are rare, aggressive, cutaneous neuroendocrine tumours, approximately 80% of which are caused by the genomic integration of Merkel cell polyomavirus (MCPyV). MCPyV-positive MCCs carry poor prognosis in approximately 70% of cases, highlighting the need for greater understanding of the oncogenic mechanisms involved in pathogenesis, progression and post-therapeutic relapse, and translation into novel therapeutic strategies. In a previous pilot study, we reported a potential relationship between MCPyV gene expression and oncogenic alternative Δ exon 6–7 TrkAIII splicing in formalin-fixed paraffin-embedded (FFPE) MCC tissues from a 12-patient cohort of >90% MCPyV-positive MCCs, diagnosed at San Salvatore Hospital, L’Aquila, Italy, characterising a new MCC subgroup and unveiling a novel potential MCPyV oncogenic mechanism and therapeutic target. This, however, could not be fully verified due to poor RNA quality and difficulty in protein extraction from FFPE tissues. Here, therefore, we extend our previous observations to confirm the relationship between MCPyV and oncogenic alternative Δ exon 6–7 TrkAIII splicing in fresh, nonfixed, MCPyV-positive MCC metastasis by detecting sequence-verified RT-PCR products, including full-length Δ exon 6–7 TrkAIII, and by Western blot detection of a 100 kDa TrkA protein isoform of identical size to 100 kDa Δ exon 6–7 TrkAIII expressed by stable transfected SH-SY5Y cells. We also report that in three MCC patients submitted for multidisciplinary treatment, including locoregional chemotherapy, MCPyV large T-antigen mRNA expression, Δ exon 6–7 TrkAIII mRNA expression and intracellular indirect immunofluorescence (IF) TrkA and phosphorylation protein isoform(s) immunoreactivity in FFPE tissues were not reduced in postchemotherapeutic-relapsed MCCs compared to pretherapeutic MCCs, extending the possible roles of this novel potential MCPyV oncogenic mechanism from MCC pathogenesis to post-therapeutic relapse and progression. Detection of alternative Δ exon 6–7 TrkAIII splicing in MCC, therefore, not only characterises a new MCPyV-positive MCC subgroup and unveils a novel potential MCPyV oncogenic mechanism but also identifies patients who may benefit from inhibitors of MCPyV T-antigen and/or TrkAIII expression or clinically approved Trk kinase inhibitors such as larotrectinib or entrectinib, which are known to inhibit activated TrkA oncogenes and to elicit durable responses in TrkA-fusion oncogene-driven cancers, supporting the call for a large-scale multicentre clinical study.

Effect of Sentinel Lymph Node Biopsy and LVI on Merkel Cell Carcinoma Prognosis and Treatment

OBJECTIVE

Prognostic factors and optimal treatment approaches for Merkel cell carcinoma (MCC) remain uncertain. This study evaluated the influences of sentinel lymph node (SLN) biopsy and lymphovascular invasion (LVI) on treatment planning and prognosis.

STUDY DESIGN

Retrospective cohort study.

METHODS

Stage 1 to 3 MCC patients treated 2005 to 2018. Predictors of nodal radiation were tested using logistic regression. Predictors of recurrence-free, disease-specific, and overall survival were tested in Cox proportional hazard models.

RESULTS

Of 122 patients, 99 were without clinically apparent nodal metastases. Of these, 76 (77%) underwent excision and SLN biopsy; 29% had metastasis in SLNs, including 20% of MCCs 1 cm or less. Primary tumor diameter, site, patient age, gender, and immunosuppressed status were not significantly associated with an involved SLN. Among patients who underwent SLN biopsy, 13 of 21 (62%) MCCs with LVI had cancer in SLNs compared with 14 of 44 (25.5%) without LVI (P = .003). Although local radiation was common, nodal radiation was infrequently employed in SLN negative (pathologic N0) patients (21.8% vs. 76.2% for patients with SLN metastases, P = .0001). Survival of patients with positive SLNs was unfavorable, regardless of completion lymphadenectomy and/or adjuvant radiation. After accounting for tumor (T) and node (N) classification, age, immunosuppression, and primary site, a positive SLN and LVI were independently associated with worse survival (LVI/recurrence-free survival [RFS]: hazard ratio [HR] 2.3 (1.04-5, P = .04; LVI/disease-specific survival [DSS]: HR 5.2 (1.8-15, P = .007); N1a vs. pN0/RFS HR 3.6 (1.42-9.3, P = .007); DSS HR5.0 (1.3-19, P = .17).

CONCLUSION

SLN biopsy assists in risk stratification and radiation treatment planning in MCC. LVI and disease in SLNs, independently associated with worse survival, constitute markers of high-risk disease warranting consideration for investigational studies.

LEVEL OF EVIDENCE

III Laryngoscope, 131:E828-E835, 2021.

Clinical Features and Prognosis of Merkel Cell Carcinoma in Elderly Patients

BACKGROUND Merkel cell carcinoma (MCC) occurs primarily among elderly patients over 70 years old, but the ability to predict the prognosis of these elderly patients is poor. This population-based study aimed to identify prognostic risk factors for elderly patients with MCC. MATERIAL AND METHODS The survival and disease information of MCC patients age 65 years or older was downloaded from the SEER database, and all data were split into 2 groups based on age 80 years, with overall survival and MCC-specific survival as the main outcome indicators. RESULTS Application of the inclusion criteria yielded 1973 patients with MCC, of whom 55.6% were age 65-80 years. Among them, 1258 were males, accounting for 63.8%. In survival analysis, factors that were significantly correlated with overall survival and MCC-specific survival were N stage, M stage, liver metastasis, and lymph node surgery. CONCLUSIONS We provide epidemiological insights into Merkel cell carcinoma in elderly patients and confirmed that patients receiving lymph node surgery have better outcomes. To the best of our knowledge, this is the first study to show that the occurrence of liver metastasis is associated with poor prognosis. Our results will help strengthen monitoring of the liver condition of elderly patients and to perform necessary lymph node surgery within the patient's tolerance.

Subcutaneous desmoplastic small round-cell tumor: An unusual primary location expanding the differential of superficial round-cell tumors

Desmoplastic small round-cell tumor (DSRCT) is a rare, aggressive malignant tumor, which in the great majority of cases arises at abdominal-pelvic sites. Nevertheless, rare cases of primary extra-abdominal tumors have been reported. In challenging cases, its molecular hallmark, the EWSR1-WT1 reciprocal translocation, can be exploited diagnostically by various molecular techniques. Herein, we report an extremely rare case of primary subcutaneous DSRCT in an effort to raise awareness among our dermatopathology colleagues by expanding the differential of superficial round-cell tumors.

The role of infectious agents in cancer of the ocular region

The purpose of the study was to investigate the association between infectious agents and the development of cancer in the ocular adnexa. A comprehensive literary study was carried out, reviewing and summarizing previous reports on the topic. A broad range of malignancies of the ocular adnexa are associated with infectious agents. A strong association and possible causal relationship between the infectious agent and the development of ocular adnexal cancer are seen in Merkel cell carcinoma (Merkel cell polyomavirus), Burkitt lymphoma (Epstein-Barr virus) and Kaposi sarcoma (human herpesvirus 8). Infection with Chlamydia psittaci has been associated with the development of extranodal marginal zone B-cell lymphoma in Italy. Human papillomavirus infection has been associated with the development of squamous cell carcinomas of the ocular adnexa, although with a highly variable reported prevalence. By exploring the role of infectious agents in the ocular adnexa and the mechanism by which they contribute to oncogenesis, the diagnostics, management and prevention of these malignancies may also improve. Antibiotic treatment and vaccines against infectious agents may be valuable in future treatment. Additionally, the presence of infectious agents within the tumours may have a prognostic or predictive value.

Polyomavirus-Positive Merkel Cell Carcinoma Derived from a Trichoblastoma Suggests an Epithelial Origin of this Merkel Cell Carcinoma

Merkel cell carcinoma (MCC), an aggressive neuroendocrine carcinoma of the skin, is to date the only human cancer known to be frequently caused by a polyomavirus. However, it is a matter of debate which cells are targeted by the Merkel cell polyomavirus (MCPyV) to give rise to the phenotypically multifaceted MCC cells. To assess the lineage of origin of MCPyV-positive MCC, genetic analysis of a very rare tumor combining benign trichoblastoma and MCPyV-positive MCC was conducted by massive parallel sequencing. Although MCPyV was found to be integrated only in the MCC part, six somatic mutations were shared by both tumor components. The mutational overlap between the trichoblastoma and MCPyV-positive MCC parts of the combined tumor implies that MCPyV integration occurred in an epithelial tumor cell before MCC development. Therefore, our report demonstrates that MCPyV-positive MCC can derive from the epithelial lineage.

INSM1 Is More Sensitive and Interpretable than Conventional Immunohistochemical Stains Used to Diagnose Merkel Cell Carcinoma

Merkel cell carcinoma (MCC) is an extremely aggressive skin cancer that must be distinguished from other basaloid cutaneous neoplasms that have different treatments and prognoses. This is sometimes challenging in small shave specimens, crushed samples, lymph nodes, and core needle biopsies. Insulinoma-associated protein 1 (INSM1) immunohistochemistry is a sensitive nuclear marker of neuroendocrine differentiation. INSM1 staining was performed on 56 MCC (47 primary tumors, 9 nodal metastases), 50 skin control cases that included basal cell carcinomas, basaloid squamous cell carcinomas, Bowen disease, sebaceous neoplasms, melanoma, and B-cell lymphomas, and 28 lymph node control cases that included metastatic neuroendocrine neoplasms, melanomas, squamous cell carcinomas, lymphomas, and adenocarcinomas. Percent of staining nuclei (0, <25%, 25% to 50%, 50% to 75%, >75%) and intensity (weak, moderate, strong) were recorded for each sample. All 56 MCC expressed INSM1. By comparison, synaptophysin, CK20, and chromogranin were expressed in 96%, 92%, and 32% of MCC, respectively. While the 3 conventional markers showed significant variability in staining intensity and distribution, INSM1 stained >75% tumor nuclei in 89% of MCC and 50% to 75% of tumor nuclei in 11%. Staining intensity was strong in 85% and moderate in 15%. None of the 50 cutaneous basaloid non-MCC neoplasms in the control group stained with INSM1, and among the lymph node controls 5 of 5 neuroendocrine neoplasms expressed INSM1, confirming that INSM1 staining cannot distinguish MCC from metastatic extracutaneous neuroendocrine carcinoma. INSM1 holds promise as a neuroendocrine marker that can distinguish MCC from its mimickers in the skin and improve detection of sentinel lymph node metastases.

Merkel Cell Carcinoma: Therapeutic Update and Emerging Therapies

Merkel cell carcinoma (MCC) is a rare but highly aggressive neuroendocrine skin cancer whose incidence has almost doubled in recent decades. Risk factors for MCC include age > 65 years, immunosuppression, sun exposure and infection by Merkel cell polyomavirus. MCC usually presents as rapidly growing, firm, red to violaceous nodule localized on the sun-exposed skin. Surgery followed by radiation therapy is considered to be the first-line treatment for primary or loco-regional MCC in order to prevent recurrences and lymph node metastasis, while chemotherapy has always been used to treat advanced forms. However, responses to chemotherapy are mostly of short duration, and the associated clinical benefit on overall survival is still unclear. The use of checkpoint inhibitors (CPIs) has shown good results in the treatment of advanced MCC and, consequently, CPIs are considered emerging immunotherapeutic options for these patients, although there are still no standardized treatments for patients with metastatic disease. Here we present a complete overview of the different possibilities for the treatment of MCC according to the stage of the disease, focusing on the emerging immunotherapies used for treating advanced MCC.

Merkel Cell Carcinoma Metastatic to Pleural Fluid: A Case Report

Merkel cell carcinoma (MCC) is a rare aggressive neuroendocrine carcinoma of the skin that shows locoregional or distant metastasis. Metastasis of MCC to body cavity effusion is extremely rare; only three cases have been reported so far. Metastatic MCC in effusion cytology shows small blue round cells with fine stippled chromatin like other small blue round cell tumors such as small cell lung carcinoma or lymphoma. The diagnosis of metastatic MCC can grant patients good chances at recently advanced therapeutic options. Here, we present a case of metastatic MCC to pleural effusion with characteristic single file-like pattern.