Merkel cell carcinoma: emerging biology, current approaches, and future directions

Understanding Merkel Cell Carcinoma: Pathogenic Signaling, Extracellular Matrix Dynamics, and Novel Treatment Approaches

Merkel cell carcinoma (MCC) is a rare but aggressive neuroendocrine skin cancer, driven by either Merkel cell polyomavirus (MCPyV) integration or ultraviolet (UV)-induced mutations. In MCPyV-positive tumors, viral T antigens inactivate tumor suppressors pRb and p53, while virus-negative MCCs harbor UV-induced mutations that activate similar oncogenic pathways. Key signaling cascades, including PI3K/AKT/mTOR and MAPK, support tumor proliferation, survival, and resistance to apoptosis. Histologically, MCC consists of small round blue cells with neuroendocrine features, high mitotic rate, and necrosis. The tumor microenvironment (TME) plays a central role in disease progression and immune escape. It comprises a mix of tumor-associated macrophages, regulatory and cytotoxic T cells, and elevated expression of immune checkpoint molecules such as PD-L1, contributing to an immunosuppressive niche. The extracellular matrix (ECM) within the TME is rich in proteoglycans, collagens, and matrix metalloproteinases (MMPs), facilitating tumor cell adhesion, invasion, and interaction with stromal and immune cells. ECM remodeling and integrin-mediated signaling further promote immune evasion and therapy resistance. Although immune checkpoint inhibitors targeting PD-1/PD-L1 have shown promise in treating MCC, resistance remains a major hurdle. Therapeutic strategies that concurrently target the TME-through inhibition of ECM components, MMPs, or integrin signaling-may enhance immune responses and improve clinical outcomes.

Genetic and molecular profiling in Merkel Cell Carcinoma: Focus on MCPyV oncoproteins and emerging diagnostic techniques

Merkel Cell Carcinoma (MCC) is an uncommon yet highly malignant form of skin cancer, frequently linked to the Merkel cell polyomavirus (MCPyV). This review comprehensively covers data from year 2000 to 2024, employing keywords such as MCC, MCPyV Oncoproteins, Immunohistochemistry, Southern Blot, Western Blot, Polymerase Chain Reaction (PCR), Digital Droplet PCR (ddPCR), Next-Generation Sequencing (NGS), and In Situ Hybridization (ISH). The search engines utilized were Google, PubMed Central, Scopus, and other journal databases like ScienceDirect. This review is essential for researchers and the broader medical community as it consolidates two decades of research on the genetic and molecular profiling of MCC, particularly focusing on MCPyV's role in its pathogenesis. It highlights the diagnostic advancements and therapeutic potential of targeting viral oncoproteins and provides insights into the development of both in vivo and in vitro models for better understanding MCC. The findings emphasize the significance of early detection, molecular diagnostics, and personalized treatment approaches, aiming to improve outcomes for patients with this malignant malignancy.

Advancing Treatment Options for Merkel Cell Carcinoma: A Review of Tumor-Targeted Therapies

Although rare, Merkel cell carcinoma (MCC) is a highly aggressive and increasingly prevalent neuroendocrine cancer of the skin. While current interventions, including surgical resection, radiation, and immunotherapy have been employed in treating many patients, those who remain unresponsive to treatment are met with sparse alternatives and a grim prognosis. For this reason, it is of interest to expand the repertoire of available therapies for MCC patients who remain resistant to current primary interventions. Recently, our improved mechanistic understanding of aberrant cell signaling observed in both MCPyV-positive and -negative MCC has facilitated exploration into several small molecules and inhibitors, among them receptor tyrosine kinase inhibitors (TKIs) and somatostatin analogs (SSAs), both of which have positively improved response rates and reduced tumor volumes upon application to treatment of MCC. The introduction of such targeted therapies into treatment protocols holds promise for more personalized care tailored towards patients of diverse subtypes, thereby improving outcomes and mitigating tumor burden, especially for treatment-resistant individuals. In this review, we characterize recent findings surrounding targeted treatments that have been applied to MCC and provide an overview of emerging perspectives on translatable options that can be further developed to offer additional therapeutic avenues for patients with the disease.

Avelumab for the treatment of locally advanced or metastatic Merkel cell carcinoma-A multicenter real-world experience in Israel

BACKGROUND

Merkel cell carcinoma (MCC) is a rare and aggressive malignancy of the skin, affecting predominantly the fair-skinned older population exposed to high levels of ultraviolet light. Immune suppression is considered a significant risk factor. With the recent advances in the field of immunotherapy, the treatment paradigm for advanced MCC, traditionally based on chemotherapy, has largely shifted to anti-PD-L1 and PD-1 agents such as avelumab and pembrolizumab, respectively. However, real-world data remain sparse. The aim of this study was to assess real-world evidence of the effectiveness of avelumab in a diverse group of patients with MCC in Israel.

METHODS

The electronic databases of five university hospitals in Israel were searched for all consecutive patients with MCC treated with at least one dose of avelumab in 2018-2022. Data on baseline, disease-related, treatment-related, and outcome parameters were collected and analyzed.

RESULTS

The cohort included 62 patients of whom 22% were immune-suppressed. The overall response rate to avelumab was 59%. The median progression-free survival was 8.1 months, and the median overall survival, 23.5 months, with no differences between immune-competent and immune-suppressed patients. Treatment was well tolerated; any-grade toxicity developed in 34% of patients, and grade 3-4 toxicity, in 14%.

CONCLUSIONS

Avelumab was found to be effective and safe for the treatment of advanced MCC in a diverse group of patients, including some with immune suppression. Further studies are warranted to evaluate the optimal sequence and duration of treatment and to assess the potential role of avelumab for earlier stages of MCC.

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

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

Multimodality imaging findings of infection-induced tumors

Several infections can predispose to certain malignancies in different body parts. These infections include viral, bacterial, and fungal pathogens. Imaging plays a vital role in the diagnosis, staging, and management of these neoplastic conditions. Furthermore, it can help in differentiating infection-related non-neoplastic processes that can mimic malignancies. Both radiologists and clinicians should be familiar with these conditions. This review discusses the epidemiology, pathogenesis, and imaging features of infection-related tumors.

Treatment of in-transit Merkel cell carcinoma by isolated limb infusion with cytotoxic drugs

Merkel cell carcinoma of the skin is a rare but aggressive malignancy, which predominantly affects older adults with fair skin. Isolated limb infusion (ILI) using melphalan and actinomycin D was first developed as a minimally invasive treatment option to treat unresectable metastatic melanoma confined to the limb. We report on a 62-year-old male with in-transit metastases (ITMs) treated with ILI to highlight the ongoing role this treatment has when all other therapies have been exhausted. At presentation, the patient had widespread ITMs in the right leg. Positron emission tomography scan demonstrated recurrent disease in the thigh and pelvis, and it was decided to treat the patient with ILI. The patient progressed well in the immediate post-operative period. The patient was able to mobilize from Day 6 post-ILI and was discharged on Day 10. There was an immediate clinical response seen in the lesions, with necrosis developing in the larger lesions.

Conditional survival estimates for merkel cell carcinoma reveal the dynamic nature of prognostication

BACKGROUND AND OBJECTIVES

Conditional survival (CS) analysis has emerged as a dynamic prognostication methodology. The goal of this study was to determine disease-specific CS rates in Merkel cell carcinoma (MCC).

METHODS

This retrospective study included patients with MCC from the Surveillance Epidemiology and End Results (SEER) registry (1988-2016). Stage-specific 5-year MCC-specific CS rates for study and survivor cohorts were estimated, and the significance of clinicopathologic factors to predict 1-year MCC-specific death was evaluated using multivariate logistic regression.

RESULTS

Within stage, 5-year CS survival rates improved with increasing survivorship. Pathologic Stage I patients had the highest 5-year CS rate at diagnosis (89.1%) but the smallest increase over time (96% among 5-year survivors). Stage IV patients experienced the greatest change in 5-year CS rates from 25.4% (at diagnosis) to 88% (5-year survivors). At diagnosis stage, age, sex, and primary site were all significantly associated with 1-year MCC-related death in the multivariate analysis. In contrast, among 5-year survivors only sex and age at diagnosis were significant predictors.

CONCLUSIONS

MCC CS rates improved across all disease stages over time. Additionally, the relationships of prognostic factors with 1-year MCC-death changed with increasing survivorship. This perspective can provide a foundation for informed decision-making.

Folate hydrolase-1 (FOLH1) is a novel target for antibody-based brachytherapy in Merkel cell carcinoma

Backgrounds

Folate Hydrolase‐1 (FOLH1; PSMA) is a type II transmembrane protein, luminally expressed by solid tumour neo‐vasculature. Monoclonal antibody (mAb), J591, is a vehicle for mAb‐based brachytherapy in FOLH1+ cancers. Brachytherapy is a form of radiotherapy that involves placing a radioactive material a short distance from the target tissue (e.g., on the skin or internally); brachytherapy is commonly accomplished with the use of catheters, needles, metal seeds and antibody or small peptide conjugates. Herein, FOLH1 expression in primary (p) and metastatic (m) Merkel cell carcinoma (MCC) is characterized to determine its targeting potential for J591‐brachytherapy.

Materials & Methods

Paraffin sections from pMCC and mMCC were evaluated by immunohistochemistry for FOLH1. Monte Carlo simulation was performed using the physical properties of conjugated radioisotope lutetium‐177. Kaplan–Meier survival curves were calculated based on patient outcome data and FOLH1 expression.

Results

Eighty‐one MCC tumours were evaluated. 67% (54/81) of all cases, 77% (24/31) pMCC and 60% (30/50) mMCC tumours were FOLH1+. Monte Carlo simulation showed highly localized ionizing tracks of electrons emitted from the targeted neo‐vessel. 42% (34/81) of patients with FOLH1+/− MCC had available survival data for analysis. No significant differences in our limited data set were detected based on FOLH1 status (p = 0.4718; p = 0.6470), staining intensity score (p = 0.6966; p = 0.9841) or by grouping staining intensity scores (− and + vs. ++, +++, +++) (p = 0.8022; p = 0.8496) for MCC‐specific survival or recurrence free survival, respectively.

Conclusions

We report the first evidence of prevalent FOLH1 expression within MCC‐associated neo‐vessels, in 60‐77% of patients in a large MCC cohort. Given this data, and the need for alternatives to immune therapies it is appropriate to explore the safety and efficacy of FOLH1‐targeted brachytherapy for MCC.

What's already known about this topic?

We report the first evidence of prevalent folate hydrolase‐1 (FOLH1; also known as prostate‐specific membrane antigen) expression within MCC‐associated neovessels.

What does this study add?

Herein, FOLH1 expression in Merkel cell carcinoma neovasculature is validated, and the therapeutic mechanism of specific, systemic targeting of disseminated disease with antibody‐based brachytherapy, is defined.

Identification of natural product modulators of Merkel cell carcinoma cell growth and survival

Merkel cell carcinoma (MCC) is a rare, but aggressive skin cancer the incidence of which has increased significantly in recent years. The majority of MCCs have incorporated Merkel cell polyomavirus (VP-MCC) while the remainder are virus-negative (VN-MCC). Although a variety of therapeutic options have shown promise in treating MCC, there remains a need for additional therapeutics as well as probes for better understanding MCC. A high-throughput screening campaign was used to assess the ability of > 25,000 synthetic and natural product compounds as well as > 20,000 natural product extracts to affect growth and survival of VN-MCC and VP-MCC cell lines. Sixteen active compounds were identified that have mechanisms of action reported in the literature along with a number of compounds with unknown mechanisms. Screening results with pure compounds suggest a range of potential targets for MCC including DNA damage, inhibition of DNA or protein synthesis, reactive oxygen species, and proteasome inhibition as well as NFκB inhibition while also suggesting the importance of zinc and/or copper binding. Many of the active compounds, particularly some of the natural products, have multiple reported targets suggesting that this strategy might be a particularly fruitful approach. Processing of several active natural product extracts resulted in the identification of additional MCC-active compounds. Based on these results, further investigations focused on natural products sources, particularly of fungal origin, are expected to yield further potentially useful modulators of MCC.

Antibody-Based Targeted Interventions for the Diagnosis and Treatment of Skin Cancers

BACKGROUND

Cutaneous malignancies most commonly arise from skin epidermal cells. These cancers may rapidly progress from benign to a metastatic phase. Surgical resection represents the gold standard therapeutic treatment of non-metastatic skin cancer while chemo- and/or radiotherapy are often used against metastatic tumors. However, these therapeutic treatments are limited by the development of resistance and toxic side effects, resulting from the passive accumulation of cytotoxic drugs within healthy cells.

OBJECTIVE

This review aims to elucidate how the use of monoclonal Antibodies (mAbs) targeting specific Tumor Associated Antigens (TAAs) is paving the way to improved treatment. These mAbs are used as therapeutic or diagnostic carriers that can specifically deliver cytotoxic molecules, fluorophores or radiolabels to cancer cells that overexpress specific target antigens.

RESULTS

mAbs raised against TAAs are widely in use for e.g. differential diagnosis, prognosis and therapy of skin cancers. Antibody-Drug Conjugates (ADCs) particularly show remarkable potential. The safest ADCs reported to date use non-toxic photo-activatable Photosensitizers (PSs), allowing targeted Photodynamic Therapy (PDT) resulting in targeted delivery of PS into cancer cells and selective killing after light activation without harming the normal cell population. The use of near-infrared-emitting PSs enables both diagnostic and therapeutic applications upon light activation at the specific wavelengths.

CONCLUSION

Antibody-based approaches are presenting an array of opportunities to complement and improve current methods employed for skin cancer diagnosis and treatment.

Predictors of False Negative Sentinel Lymph Node Biopsy in Clinically Localized Merkel Cell Carcinoma

BACKGROUND

Sentinel lymph node biopsy (SLNB) is routinely recommended for clinically localized Merkel cell carcinoma (MCC); however, predictors of false negative (FN) SLNB are undefined.

METHODS

Patients from six centers undergoing wide excision and SLNB for stage I/II MCC (2005-2020) were identified and were classified as having either a true positive (TP), true negative (TN) or FN SLNB. Predictors of FN SLNB were identified and survival outcomes were estimated.

RESULTS

Of 525 patients, 28 (5.4%), 329 (62.7%), and 168 (32%) were classified as FN, TN, and TP, respectively, giving an FN rate of 14.3% and negative predictive value of 92.2% for SLNB. Median follow-up for SLNB-negative patients was 27 months, and median time to nodal recurrence for FN patients was 7 months. Male sex (hazard ratio [HR] 3.15, p = 0.034) and lymphovascular invasion (LVI) (HR 2.22, p = 0.048) significantly correlated with FN, and increasing age trended toward significance (HR 1.04, p = 0.067). The 3-year regional nodal recurrence-free survival for males >75 years with LVI was 78.5% versus 97.4% for females ≤75 years without LVI (p = 0.009). Five-year disease-specific survival (90.9% TN vs. 51.3% FN, p < 0.001) and overall survival (69.9% TN vs. 48.1% FN, p = 0.035) were significantly worse for FN patients.

CONCLUSION

Failure to detect regional nodal microscopic disease by SLNB is associated with worse survival in clinically localized MCC. Males, patients >75 years, and those with LVI may be at increased risk for FN SLNB. Consideration of increased nodal surveillance following negative SLNB in these high-risk patients may aid in early identification of regional nodal recurrences.

Clinical impact of immunotherapy in Merkel cell carcinoma patients: A systematic review and meta-analysis

BACKGROUND

Immunotherapy is emerging as an alternative treatment for Merkel cell carcinoma, but its long-term effects on response, survival, and safety are not well established. High-quality evidence is needed to estimate the efficacy of this treatment and to review the characteristics of patients and tumors that might improve outcomes.

OBJECTIVE

To summarize efficacy and safety of immunotherapy in patients with Merkel cell carcinoma.

METHODS

A systematic review was performed for studies published in MEDLINE, Web of Science, Scopus, and EMBASE. Two reviewers examined the literature and data extraction in duplicate. We estimated the proportions for objective responses, progression-free survival, overall survival, and treatment-related adverse events. Associations between objective response rate and immunobiologic markers were analyzed.

RESULTS

Six clinical trials of 201 patients treated with immunotherapy were included. The objective response rate was 51% (95% confidence interval, 0.40-0.62; I² = 37.1%) and grade ≥3 treatment-related adverse events were observed in 18% (95% confidence interval, 0.11-0.29; I² = 49.5%) of patients. No significant difference was observed between response rates and immunobiologic characteristics.

CONCLUSIONS

A significantly reduced tumor diameter with durable response rates and a safe profile are obtained with immunotherapy. Similar response rates achieved on either subgroup of viral status or programmed death ligand 1 expression suggests that it might act on multiple, unexplored pathways.

Nomogram prediction for the overall survival and cancer-specific survival of patients diagnosed with Merkel cell carcinoma

Background

Merkel cell carcinoma (MCC) is a rare and aggressive neuroendocrine carcinoma of the skin, with a high recurrence rate and a high mortality rate worldwide. The purpose of this article is to construct a nomogram that incorporates significant clinical parameters and predicts the survival of individuals with MCC.

Methods

The Surveillance, Epidemiology, and End Results (SEER) database was employed to retrospectively analyze all confirmed MCC cases from 2004 to 2015. The data was collected from 3,688 patients, and was randomized as the training or validation group (1:1 ratio). The independent factors which predicted the cancer-specific survival (CSS) and overall survival (OS) for MCC cases were searched for nomogram construction respectively. Independent parameters that affected CSS were determined using the Fine and Gray competing risk regression model. In addition, the time-dependent receiver operating characteristic (ROC) curve was constructed. Then, the area under the curve (AUC) values, calibration curve, and the concordance index (C-index) were used to determine the nomogram performance. At last, decision curve analysis (DCA) was conducted to determine the net clinical benefit.

Results

The multivariate analysis results revealed that sex, age, race, marriage, American Joint Committee on Cancer (AJCC) stage, chemotherapy and radiotherapy were independent OS prognostic factors. Furthermore, competing risk analysis showed age, sex, AJCC stage, chemotherapy were the independent CSS prognostic factors. For validation, the C-index value of OS nomogram was 0.703 (95% CI: 0.686-0.721), while C-index value of CSS nomogram was 0.737 (95% CI: 0.710-0.764). Both C-index and AUC suggested that nomograms had superior performance to that of the AJCC stage system. In addition, according to the calibration curve, both nomograms were capable of accurate prediction of MCC prognosis. The DCA showed that the net benefits of the nomograms were superior among various threshold probabilities than these of AJCC stage system.

Conclusions

The present work established and verified the novel nomograms to predict the OS and CSS of MCC patients. If further confirmed in future studies, it may become another helpful tool for risk stratification and management of MCC patients.

Glucose-6-phosphate dehydrogenase correlates with tumor immune activity and programmed death ligand-1 expression in Merkel cell carcinoma

Background

Merkel cell carcinoma (MCC) is a rare and highly malignant skin cancer. Some cases have a good prognosis and spontaneous regression can occur. Reported prognostic markers, such as Merkel cell polyoma virus infection or programmed death ligand-1 (PD-L1) expression, remain insufficient for precisely estimating the vastly different patient outcomes. We performed RNA sequencing to evaluate the immune response and comprehensively estimate prognostic values of immunogenic factors in patients with MCC.

Methods

We collected 90 specimens from 71 patients and 53 blood serum samples from 21 patients with MCC at 10 facilities. The mRNA was extracted from formalin-fixed paraffin-embedded tissues. Next-generation sequencing, immunohistochemical staining and blood serum tests were performed.

Results

Next-generation sequencing results classified MCC samples into two types: the ‘immune active type’ was associated with better clinical outcomes than the ‘cell division type’. Expression of the glucose-6-phosphate dehydrogenase (G6PD) gene was highly significantly upregulated in the ‘cell division type’. Among 395 genes, G6PD expression correlated with the presence of lymph node or distant metastases during the disease course and significantly negatively correlated with PD-L1 expression. Immunohistochemical staining of G6PD also correlated with disease-specific survival and exhibited less heterogeneity compared with PD-L1 expression. G6PD activity could be measured by a blood serum test. The detection values significantly increased as the cancer stage progressed and significantly decreased after treatment.

Conclusions

G6PD expression was an immunohistochemically and serum-detectable prognostic marker that negatively correlated with immune activity and PD-L1 levels, and could be used to predict the immunotherapy response.

Spontaneous regression of Markel cell carcinoma in anterior mediastinum without cutaneous involvement

Background:

Merkel cell carcinoma (MCC) is a rare and highly aggressive neuroendocrine malignancy typically involving the skin. The majority of MCC involves the head/neck region and the extremities. Despite the aggressive nature of the disease, there have been several case studies that report spontaneous regression. We report a unique case of spontaneous regression of an MCC in a peculiar region in the anterior mediastinum with no cutaneous involvement.

Methods:

A 50-year-old man who presented with a mobile low anterior neck mass, proven by biopsy, to be MCC. Subsequent PET/CT confirmed an FDG (Flurodeoxyglucose)-avid upper mediastinal mass. The mass gradually regressed over the course of 1 month subsequent to biopsy and was no longer palpable on exam or visible on subsequent CT scans. The patient was treated with intensity modulated radiation therapy with a total dose of 6,160 cGy in 28 fractions to the site of previously visible primary disease. At-risk nodal basins were also treated. On subsequent follow-up, the patient continued to have no clinical or radiographic signs of disease.

Discussion:

Spontaneous regression of an MCC is rare but has been reported mostly in the head/neck region following biopsy. It is unknown why spontaneous regression occurs. There is a possibility that biopsy may stimulate T-lymphocytes resulting in spontaneous regression.

Conclusion:

This is the first case to our knowledge of spontaneous regression of an MCC in the anterior mediastinum with no cutaneous involvement. Most MCC are seen clinically due to skin changes with a majority of cases occurring in the head/neck region.

Interesting case of an abdominal wall Merkel cell carcinoma highlighting the importance of developing an Australian clinical practice guideline

A 66-year-old Australian male farmer was referred for management of an asymptomatic, rapidly expanding, anterior abdominal wall mass. It was firm and well circumscribed. There were no overlying skin changes, constitutional symptoms or weight loss. His medical history included small bowel obstruction and resection from a Meckel's diverticulitis and a 40-pack-year smoking history. Core biopsy was suggestive of a neuroendocrine tumour and Gallium-68-Dodecane-Tetraacetic-Acid (68GaTate) positron emission tomography revealed an avid solitary lesion confined to the subcutaneous space in the left anterior abdominal wall. Wide local excision was performed, and histopathology revealed Merkel cell carcinoma (MCC). Although classically regarded as a primary cutaneous neuroendocrine tumour, MCC may originate from the subcutaneous fat without obvious skin involvement. Older patients with asymptomatic, rapidly enlarging lesions, particularly if immunosuppressed, with significant ultraviolet sunlight exposure, should raise a high index of suspicion for MCC. Like melanoma, non-metastatic MCC should be treated aggressively for best prognosis.

Use of Intraoperative Radioguidance in Recurrent Merkel Carcinoma

Merkel cell carcinoma is a rapidly progressive nonmelanoma skin cancer with a high risk of recurrence. When recurrence occurs, it is associated with poor prognosis and there is a lack of guidelines for the management of such cases. This article describes a challenging case in which the innovative use of iodine-125 radioactive seeds permitted us to precisely identify and resect two nonpalpable recurrent nodules. The safety and accuracy of the surgical procedure were compromised by the presence of scar tissue following two past resections and two courses of radiotherapy. Radioactive seed localization is a well-known procedure in breast cancer, demonstrating potential for an extended application in other cancer types and in complex clinical situations.

Bone marrow involvement with Merkel cell carcinoma

Merkel cell carcinoma (MCC) is a rare but highly aggressive cutaneous tumour. Most tumours occur in the head and neck, extremities or torso and 36% of them involve the face. Bone marrow involvement in MCC is rare and to our knowledge only nine cases reported in the English literature. Bone marrow biopsy is not usually performed to stage MCC; thus, the true incidence of bone marrow involvement may be under-reported. The majority of the cases reported in the literature have some form of immunosuppression, which suggests a strong association. We report a case of extensive bone marrow involvement from MCC in an 80-year-old Caucasian woman with a history of rheumatoid arthritis treated with adalimumab, methotrexate and prednisone. It may be prudent to include bone marrow biopsy in the staging of MCC in immune-compromised patients.

An Unusual Presentation of Merkel Cell Carcinoma in a HIV Patient: A Case Report and Literature Review

Merkel cell carcinoma (MCC) is a rare, rapidly growing, aggressive neuroendocrine skin cancer that generally arises on sun-exposed areas of body such as head, neck, upper limbs, and shoulders of people with light complexity. Typically, MCC presents as shiny, flesh-colored or bluish-red, intracutaneous nodule, possibly with ulceration or crusting. In most of the cases, there is an association with Merkel cell polyomavirus. Even though these are very aggressive tumors, early detection and treatment has always given favorable outcome. There seems to be no consensus in definite prognostic markers, and advanced stages have the worst outcome even with treatment. There has been a recent trend in using PD-I/PD-L1 target therapy rather than chemotherapy in these cancers and have shown to improve survival by many months. In this article, we report a very unusual presentation of MCC first found on left frontoparietal skull as an 8-cm diameter fixed, subcutaneous mass without any typical features of MCC and was found to have metastatic spread to lung and liver. The patient was treated with palliative radiotherapy to brain and chemotherapy with cisplatin/etoposide with addition of immunotherapy later.

Artesunate Affects T Antigen Expression and Survival of Virus-Positive Merkel Cell Carcinoma

Merkel cell carcinoma (MCC) is a rare and highly aggressive skin cancer with frequent viral etiology. Indeed, in about 80% of cases, there is an association with Merkel cell polyomavirus (MCPyV); the expression of viral T antigens is crucial for growth of virus-positive tumor cells. Since artesunate—a drug used to treat malaria—has been reported to possess additional anti-tumor as well as anti-viral activity, we sought to evaluate pre-clinically the effect of artesunate on MCC. We found that artesunate repressed growth and survival of MCPyV-positive MCC cells in vitro. This effect was accompanied by reduced large T antigen (LT) expression. Notably, however, it was even more efficient than shRNA-mediated downregulation of LT expression. Interestingly, in one MCC cell line (WaGa), T antigen knockdown rendered cells less sensitive to artesunate, while for two other MCC cell lines, we could not substantiate such a relation. Mechanistically, artesunate predominantly induces ferroptosis in MCPyV-positive MCC cells since known ferroptosis-inhibitors like DFO, BAF-A1, Fer-1 and β-mercaptoethanol reduced artesunate-induced death. Finally, application of artesunate in xenotransplanted mice demonstrated that growth of established MCC tumors can be significantly suppressed in vivo. In conclusion, our results revealed a highly anti-proliferative effect of the approved and generally well-tolerated anti-malaria compound artesunate on MCPyV-positive MCC cells, suggesting its potential usage for MCC therapy.

The Possibility of Using Genotoxicity, Oxidative Stress and Inflammation Blood Biomarkers to Predict the Occurrence of Late Cutaneous Side Effects after Radiotherapy

Despite the progresses performed in the field of radiotherapy, toxicity to the healthy tissues remains a major limiting factor. The aim of this work was to highlight blood biomarkers whose variations could predict the occurrence of late cutaneous side effects. Two groups of nine patients treated for Merkel Cell Carcinoma (MCC) were established according to the grade of late skin toxicity after adjuvant irradiation for MCC: grade 0, 1 or 2 and grade 3 or 4 of RTOG (Radiation Therapy Oncology Group)/EORTC (European Organization for Research and Treatment of Cancer). To try to discriminate these 2 groups, biomarkers of interest were measured on the different blood compartments after ex vivo irradiation. In lymphocytes, cell cycle, apoptosis and genotoxicity were studied. Oxidative stress was evaluated by the determination of the erythrocyte antioxidant capacity (superoxide dismutase, catalase, glutathione peroxidase, reduced and oxidized glutathione) as well as degradation products (protein carbonylation, lipid peroxidation). Inflammation was assessed in the plasma by the measurement of 14 cytokines. The most radiosensitive patients presented a decrease in apoptosis, micronucleus frequency, antioxidant enzyme activities, glutathione and carbonyls; and an increase in TNF-a (Tumor Necrosis Factor a), IL-8 (Interleukin 8) and TGF-β1 (Transforming Growth Factor β1) levels. These findings have to be confirmed on a higher number of patients and before radiotherapy and could allow to predict the occurrence of late skin side effects after radiotherapy.

Merkel Cell Carcinoma Outcomes: Does AJCC8 Underestimate Survival?

INTRODUCTION

The eighth edition of the American Joint Committee on Cancer (AJCC8) Staging Manual provides important information for staging and prognostication; however, survival estimates for patients with Stage I-III Merkel cell carcinoma (MCC), a rare disease, may be as practical using data from large-volume centers as that collated for the AJCC analysis. As such, we compared our institutional outcomes to AJCC8.

METHODS

Patients who presented from 2005 to 2017 with MCC to two high-volume centers were included. Demographics, clinicopathologic characteristics, survival and recurrence data were compiled, and outcomes compared to AJCC8.

RESULTS

A total of 409 patients were included. Median age was 75 (range 29-98) years, and 68% were male. Median follow-up was 16 months (0-157). Five-year overall survival (OS) was 70%; 5-year disease-specific survival (DSS) was 84%. When stratified by extent of disease, 5-year OS was higher for patients with local disease compared to those with nodal disease (72.6% vs 62.7%, p=0.005). Similarly, patients with local disease had higher 5-year DSS than those with nodal disease (90.1% vs 76.8%, p=0.002). Five-year recurrence-free survival was 59.2% for all patients, 65.0% for local disease and 48.3% for nodal disease (p=0.033).

CONCLUSIONS

Here, MCC patients with local or nodal disease have substantially higher OS rates than predicted in AJCC8 (5-year: 72.6% vs 50.6%; 62.7% vs 35.4%, respectively). Importantly, 5-year DSS was significantly better than the OS rates reported presently and in AJCC8. As clinicians and patients rely on AJCC to accurately prognosticate and guide treatment decisions, these estimates should be reassessed and updated to more accurately predict survival outcomes.

Advances in the Understanding of Skin Cancer: Ultraviolet Radiation, Mutations, and Antisense Oligonucleotides as Anticancer Drugs

Skin cancer has always been and remains the leader among all tumors in terms of occurrence. One of the main factors responsible for skin cancer, natural and artificial UV radiation, causes the mutations that transform healthy cells into cancer cells. These mutations inactivate apoptosis, an event required to avoid the malignant transformation of healthy cells. Among these deadliest of cancers, melanoma and its 'younger sister', Merkel cell carcinoma, are the most lethal. The heavy toll of skin cancers stems from their rapid progression and the fact that they metastasize easily. Added to this is the difficulty in determining reliable margins when excising tumors and the lack of effective chemotherapy. Possibly the biggest problem posed by skin cancer is reliably detecting the extent to which cancer cells have spread throughout the body. The initial tumor is visible and can be removed, whereas metastases are invisible to the naked eye and much harder to eliminate. In our opinion, antisense oligonucleotides, which can be used in the form of targeted ointments, provide real hope as a treatment that will eliminate cancer cells near the tumor focus both before and after surgery.

A rare case of Merkel cell carcinoma with ovarian metastasis

Introduction

Merkel cell carcinoma (MCC) is a rare cutaneous malignancy that normally occurs in sun-exposed areas of the skin. Risk factors are immundeficency and Merkel cell polyomavirus.

Treatment options are surgery, radiotherapy, chemotherapy and immunotherapy in clinical trials.

Case report

We describe a case of an 80-year-old woman with ovarian metastasis of MCC six years after excision of a cutaneous MCC on the cheek.

Discussion

To our knowledge only three cases with ovarian metastasis of MCC have been described so far. Our case is the second with distant metastasis to the ovary spreading from a primary tumor in the skin of the head, in the other two cases the primary tumor was in the inguinal skin.

Conculsion

MCC is a highly aggressive cutaneous and mucosal malignancy with frequent recurrence, lymph node and distant metastases. There is no clear consensus how to treat metastatic disease.

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MCC is a rare malignancy.

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Recurrence and metastases are frequent.

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There is little knowledge of treatments for metastatic MCC.

A case report of recurrent Merkel cell carcinoma with synchronous metastases to the heart and stomach

RATIONALE

Merkel cell carcinoma (MCC) is an aggressive, rare neuroendocrine skin cancer. MCC metastasis to the heart is exceedingly rare and gastric metastases from MCC have rarely been reported.

PATIENT CONCERNS

We described the case of an 82-year-old man diagnosed with recurrent MCC with cardiac and gastric metastasis who presented with poor oral intake and severe weight loss. The patient was diagnosed with MCC 3 years ago and treated with surgical resection and radiation.

INTERVENTIONS

We performed stomach biopsy in edematous lesion. And fluoroscopy and ultrasound guided biopsy of the cardiac mass was performed.

DIAGNOSES

MCC with synchronous metastases to the heart and stomach.

OUTCOMES

The primary lesion had complete resolution and the patient remained disease free on regular follow-up every 6 months for 2 and half years. After MCC recurred, palliative anti-cancer therapy was considered but could not be performed due to the patient's poor performance status involved elderly, combined recurrent pneumonia.

LESSONS

To our best knowledge, this is the first report of synchronous cardiac and gastric metastasis from cutaneous MCC worldwide. Although uncommon, MCC should be considered in clinical cases of synchronous metastasis.

Merkel cell carcinoma masquerading as cellulitis: a case report and review of the literature

Merkel cell carcinoma (mcc) is an uncommon malignancy of the skin arising from cells located in the deeper layers of the epidermis called Merkel cells. This malignancy rarely presents as a metastatic disease, and the field is therefore deficient in regards to management. We report the case of a 49-year-old woman who presented with a presumptive diagnosis of osteomyelitis of the left fifth digit that was resistant to treatment with antibiotics; she underwent debridement of the digit that revealed mcc and was later to have metastatic disease to her lungs, liver, and musculoskeletal system. The management of mcc, although simple in the early stage of the disease, can become challenging when it is more advanced. Multiple new modalities for its treatment have emerged over the last few years, and more recently, clinical trials are being conducted for the use of immunotherapy agents in the treatment of this malignancy.

Merkel cell carcinoma in an immunosuppressed patient

Merkel cell carcinoma is an uncommon neuroendocrine carcinoma with a rising incidence and an aggressive behavior. It predominantly occurs in older patients, with onset occurring at a mean age of 75-80 years. Recognized risk factors are ultraviolet sunlight exposure, immunosuppression, and, more recently, Merkel cell polyomavirus. We report a case of Merkel cell carcinoma in a young HIV positive patient with Merkel Cell polyomavirus detected in the tumor.

A rare case of Merkel cell carcinoma presenting as a giant intra-thoracic mass: A case report and review of the literature

RATIONALE

Merkel cell carcinoma (MCC) is an aggressive neuroendocrine-derived cutaneous cancer. Ectopic or single metastatic MCC located in thorax is extremely rare; meanwhile, its definite management has not been elucidated yet.

PATIENT CONCERNS

A 64-year-old female patient with a giant mass located in her left thorax was presented for stuffy pain of left chest for 6 months and fever for half a month. She underwent radical resection of vulvar MCC 10 years ago.

DIAGNOSES

Computed tomography (CT)-guided biopsy of the intrathoracic mass revealed a diagnosis of MCC, without synchronous urogenital lesions on pelvic CT images.

INTERVENTIONS

This bulky tumor was completely resected via thoracotomy, along with the adjacent pulmonary lobe, pericardium, pleura, and diaphragm.

OUTCOMES

The patient survived without local-regional recurrence or distant metastasis during the follow-up of 1 year up to now.

LESSONS

Ectopic or single metastatic MCC should be considered in the differential diagnosis of intrathoracic tumors, especially in patients with a history of MCC. Besides, a timely surgery combined with chemotherapy is effective for this disease.

Epidemiology of skin cancer in the mature patient

Epidermal cancers include keratinocyte cancer, melanocyte cancer, and Merkel cell carcinoma. These cancers account for the vast majority of new cancers diagnosed in Australia, North America, and Europe. Keratinocyte cancer is the most common epidermal cancer and accounts for 7 out of 8 new cancers diagnosed in Australia. Melanoma and Merkel cell carcinoma are less common than keratinocyte carcinoma but are more important causes of mortality in Australia. Keratinocyte cancer has also been demonstrated to be a marker of cancer-prone phenotype. Risk factors for epidermal cancer include intrinsic and environmental factors, in particular exposure to ultraviolet radiation and advanced age. Actinic keratosis has an approximate prevalence of 79% of men and 68% of women between 60 and 69 years of age, and has a low risk of malignant transformation into squamous cell carcinoma. Basal cell carcinoma is the most common malignancy in Caucasians worldwide, with the incidence increasing by 2% per year in Australia. Squamous cell carcinoma is the second most common epidermal cancer, with an incidence of approximately 1035 or 472 per 100,000 person-years in men and women, respectively. Primary risk factors for both basal cell carcinoma and squamous cell carcinoma include light skin color, UV radiation exposure, and chronic immunosuppression. Although the rate of melanoma is increasing, the mortality in Australia is reducing and is currently 9%. The overall incidence of melanoma in Australia is approximately 50 cases per 100,000 persons (62 for men and 40 for women). Keratinocyte carcinoma and melanoma are risk factors for developing further skin cancer and primary malignancy. This contribution reviews the incidence, prevalence, and risk factors associated with the development of epidermal cancer and premalignant epidermal neoplasia.

A Red Nodule on the Cheek - a Case Report

Introduction: Merkel cell carcinoma (MCC) is a rare, very aggressive neuroectodermal tumor of the skin typically located on sun-exposed areas and frequently found in Caucasian men between 70 and 80 years of age.

Case Report: We present a case of a 86-year-old woman who was referred to our Skin Cancer Unit with a red and well defined nodule located on her left commissure of the mouth, that grew during a couple of months and was completely asymptomatic. Dermoscopic examination revealed a reddish background with linear and arborizing irregular vessels, some out of focus vessels and whitish areas. The lesion was excised, histological examination showed that the tumor was hypercellular and composed of round epithelial elements with large nuclei and scant cytoplasm suggestive of MCC. Immunohistochemical stains confirmed a diffuse positivity with cytokeratin (CK) 2 chromogranin, and synaptophysin; CK7 and thyroid transcription factor-1(TTF-1) were negative. Sentinel lymph node biopsy was done, resulting negative for neoplastic cells, and computed tomography (CT) of the chest, abdomen and pelvis showed no distant metastasis. Adjuvant radiotherapy on the tumor site and on homolateral neck lymph nodes was also done.

Conclusion: Merkel cell carcinoma presents as an asymptomatic, rapidly growing nonpigmented nodule without specific characteristics. Dermoscopic features may help to distinguish MCC from other similar tumors: linear irregular vessels, milky pink areas, architectural disorders and structureless areas, even if not specific, when present are strongly suggestive of MCC. Wide excision with 2 cm margins with adjuvant radiotherapy is the treatment of choice in high-risk primary tumors, while sentinel lymph node biopsy and computed tomography scans are necessary for early diagnosis of metastatic disease.

Anaplastic Lymphoma Kinase in Cutaneous Malignancies

Anaplastic lymphoma kinase (ALK) is a receptor tyrosine kinase that has been implicated in the pathogenesis of a variety of neoplasms. As suggested by its name, ALK was first described as part of a translocation product in cases of anaplastic large-cell lymphoma, with other genetic and cytogenetic ALK mutations subsequently coming to attention in the development of many other hematologic and solid organ malignancies. ALK has now been shown to play a role in the pathogenesis of several cutaneous malignancies, including secondary cutaneous systemic anaplastic large-cell lymphoma (ALCL) and primary cutaneous ALCL, melanoma, spitzoid tumors, epithelioid fibrous histiocytoma, Merkel cell carcinoma, and basal cell carcinoma. The characterization of ALK-positivity in these cutaneous malignancies presents exciting opportunities for utilizing ALK-targeted inhibitors in the treatment of these diseases.

Subacute Cerebellar Degeneration due to a Paraneoplastic Phenomenon Associated with Metastatic Merkel Cell Carcinoma: A Case Report

Purpose

The aim of this article is to illustrate the diagnostic challenges and management of paraneoplastic neurological syndromes in Merkel cell carcinoma.

Materials and Methods

We describe a previously functionally independent 85-year-old woman who presented with subacute onset of dizziness and gait ataxia in the setting of metastatic Merkel cell carcinoma.

Results

Diagnosis was made on biopsy after positron emission tomography imaging revealed increased metabolic activity in 2 left inguinofemoral lymph nodes. Cerebrospinal fluid analysis was positive for anti-Hu on subsequent admission. Her functional status improved with methylprednisolone treatment and radiotherapy.

Conclusion

The case highlights the challenge of the evaluation of patients who present with progressive cerebellar signs and the need to consider a paraneoplastic syndrome, especially in the setting of previous malignancy.

Rationale for immune-based therapies in Merkel polyomavirus-positive and -negative Merkel cell carcinomas

Merkel cell carcinoma (MCC) is a rare but often deadly skin cancer that is typically caused by the Merkel cell polyomavirus (MCPyV). Polyomavirus T-antigen oncoproteins are persistently expressed in virus-positive MCCs (˜80% of cases), while remarkably high numbers of tumor-associated neoantigens are detected in virus-negative MCCs, suggesting that both MCC subsets may be immunogenic. Here we review mechanisms by which these immunogenic tumors evade multiple levels of host immunity. Additionally, we summarize the exciting potential of diverse immune-based approaches to treat MCC. In particular, agents blocking the PD-1 axis have yielded strikingly high response rates in MCC as compared with other solid tumors, highlighting the potential for immune-mediated treatment of this disease.

National Institutes of Health Hematopoietic Cell Transplantation Late Effects Initiative: The Subsequent Neoplasms Working Group Report

Subsequent neoplasms (SN) after hematopoietic cell transplantation (HCT) cause significant patient morbidity and mortality. Risks for specific SN types vary substantially, with particularly elevated risks for post-transplantation lymphoproliferative disorders, myelodysplastic syndrome/acute myeloid leukemia, and squamous cell malignancies. This document provides an overview of the current state of knowledge regarding SN after HCT and recommends priorities and approaches to overcome challenges and gaps in understanding. Numerous factors have been suggested to affect risk, including patient-related (eg, age), primary disease-related (eg, disease type, pre-HCT therapies), and HCT-related characteristics (eg, type and intensity of conditioning regimen, stem cell source, development of graft-versus-host disease). However, gaps in understanding remain for each of these risk factors, particularly for patients receiving HCT in the current era because of substantial advances in clinical transplantation practices. Additionally, the influence of nontransplantation-related risk factors (eg, germline genetic susceptibility, oncogenic viruses, lifestyle factors) is poorly understood. Clarification of the magnitude of SN risks and identification of etiologic factors will require large-scale, long-term, systematic follow-up of HCT survivors with detailed clinical data. Most investigations of the mechanisms of SN pathogenesis after HCT have focused on immune drivers. Expansion of our understanding in this area will require interdisciplinary laboratory collaborations utilizing measures of immune function and availability of archival tissue from SN diagnoses. Consensus-based recommendations for optimal preventive, screening, and therapeutic approaches have been developed for certain SN after HCT, whereas for other SN, general population guidelines are recommended. Further evidence is needed to specifically tailor preventive, screening, and therapeutic guidelines for SN after HCT, particularly for unique patient populations. Accomplishment of this broad research agenda will require increased investment in systematic data collection with engagement from patients, clinicians, and interdisciplinary scientists to reduce the burden of SN in the rapidly growing population of HCT survivors.

Merkel cell carcinoma occurring in a black woman: a case report

BACKGROUND

Merkel cell carcinoma is a rare, very aggressive neuroectodermal tumor of the skin. It is typically located on sun-exposed skin and frequently found in white men aged between 70 and 80 years.

CASE PRESENTATION

We report a case of a 58-year-old black woman diagnosed with Merkel cell carcinoma of the posterior face of the right elbow. She had biopsy excision and was lost to follow-up. Four months later, she presented with recurrent disease on the inferior third of the right arm with three ipsilateral axillary lymph node metastases. Amputation of the right arm and ipsilateral axillary lymph node dissection were performed, followed by adjuvant radiotherapy. Six months later, the patient died as a result of respiratory failure caused by lung metastasis. To the best of our knowledge, no specific studies have been done comparing the course and the characteristics of Merkel cell carcinoma in white and black populations, and no similar case has been reported in the literature.

CONCLUSIONS

The Merkel cell carcinoma is very rare in black people. As described elsewhere in the literature, our patient had a poor outcome despite radical management. To date, to the best of our knowledge, there has been no comparison of the prognosis of this tumor in white and black populations.

Antibody-Drug Conjugates for Cancer Therapy

Antibody–drug conjugates (ADCs) take advantage of the specificity of a monoclonal antibody to deliver a linked cytotoxic agent directly into a tumour cell. The development of these compounds provides exciting opportunities for improvements in patient care. Here, we review the key issues impacting on the clinical success of ADCs in cancer therapy. Like many other developing therapeutic classes, there remain challenges in the design and optimisation of these compounds. As the clinical applications for ADCs continue to expand, key strategies to improve patient outcomes include better patient selection for treatment and the identification of mechanisms of therapy resistance.

Squamous Cell Carcinoma In Situ Overlying Merkel Cell Carcinoma

Background:

Merkel cell carcinoma (MCC) is a rare and aggressive cutaneous neoplasm that has exhibited an exponential increase in incidence in the past 3 decades. Combined MCC and cutaneous squamous cell carcinoma (SCC/MCC) is an uncommon variant of MCC that exhibits worse prognosis than pure MCC.

Objective:

To describe the clinical presentation, dermoscopy, and histology of an unusual subtype of combined SCC/MCC.

Methods and Results:

A 73-year-old white woman presented with an ulcerated and violaceous 10-mm plaque on her right jawline that had been present for 2 to 3 months. On dermoscopy, the lesion was predominantly milky pink to red with peripheral crusting and large-caliber polymorphous vessels. Histology revealed SCC in situ above and adjacent to MCC. The tumor was excised with clear margins, and sentinel lymph node scintography was negative for nodal involvement.

Genomic portfolio of Merkel cell carcinoma as determined by comprehensive genomic profiling: implications for targeted therapeutics

Merkel cell carcinoma is an ultra-rare cutaneous neuroendocrine cancer for which approved treatment options are lacking. To better understand potential actionability, the genomic landscape of Merkel cell cancers was assessed. The molecular aberrations in 17 patients with Merkel cell carcinoma were, on physician request, tested in a Clinical Laboratory Improvement Amendments (CLIA) laboratory (Foundation Medicine, Cambridge, MA) using next-generation sequencing (182 or 236 genes) and analyzed by N-of-One, Inc. (Lexington, MA). There were 30 genes harboring aberrations and 60 distinct molecular alterations identified in this patient population. The most common abnormalities involved the TP53 gene (12/17 [71% of patients]) and the cell cycle pathway (CDKN2A/B, CDKN2C or RB1) (12/17 [71%]). Abnormalities also were observed in the PI3K/AKT/mTOR pathway (AKT2, FBXW7, NF1, PIK3CA, PIK3R1, PTEN or RICTOR) (9/17 [53%]) and DNA repair genes (ATM, BAP1, BRCA1/2, CHEK2, FANCA or MLH1) (5/17 [29%]). Possible cognate targeted therapies, including FDA-approved drugs, could be identified in most of the patients (16/17 [94%]). In summary, Merkel cell carcinomas were characterized by multiple distinct aberrations that were unique in the majority of analyzed cases. Most patients had theoretically actionable alterations. These results provide a framework for investigating tailored combinations of matched therapies in Merkel cell carcinoma patients.

Unexpected maspin immunoreactivity in Merkel cell carcinoma

Merkel cell carcinoma (MCC) is a rare but aggressive cutaneous neuroendocrine tumor, which multifactorial etiopathogenesis seems to be related to ultraviolet radiation, Merkel cell polyomavirus (MCV), and immunosuppression. In this paper, we present three cases of diagnosed MCC in apparently healthy Caucasians, two of them located in a sun-exposed area. They represented 0.25 % of all cutaneous malignant tumors diagnosed in our department. In the first case, MCC was diagnosed in the frontal region of a 67-year-old male, the second case was located in the right thigh of a 55-year-old female, whereas the third case involved the upper trunk of a 62-year-old female. All of these cases were diagnosed in the pT1 stage, having a diameter smaller than 2 cm, but the invasion depth involved the hypodermis. Microscopically, they consisted of small cells with round-oval nuclei having finely dispersed chromatin and well-defined nucleoli. Immunohistochemically, the tumor cells displayed positivity for keratin 20 and neuroendocrine markers, being negative for keratin 7 and S100 protein. Maspin immunoreactivity was seen in cases 1 and 3. Not one of the cases expressed DOG-1 or even TTF-1. Furthermore, this is the first report in literature about maspin positivity in MCC that might be related to sun exposure.