Milestones in the staging, classification, and biology of Merkel cell carcinoma

Surgical treatment of Merkel cell carcinoma of the head and neck: Experiences from a single-center cohort

Merkel cell carcinoma (MCC) is a rare malignancy, with about half of cases affecting the head and neck region. This retrospective study evaluated risk factors and survival outcomes in 89 patients (47 females, 42 males, median age: 77 years) treated with curative surgical therapy ± adjuvant therapy at a single center from 2010 to 2023. Most patients (71.9 %) presented with UICC stage I-II disease, while 28.1 % were diagnosed with stage III disease. Among the 55 patients undergoing surgical neck management, the lymph node metastasis rate was 40.0 %. Adjuvant therapy was completed in 67.5 % of patients. In the 81 patients eligible for survival analysis, the two-year overall survival (OS) was 78.8 %, and disease-free survival (DFS) was 57.2 %. Multivariable Cox regression identified completion of adjuvant therapy as a statistically significant factor of improved OS (HR 0.154; p = 0.00611). UICC stage III was significantly associated with worse DFS (HR 10.507; p = 0.00656). Additionally, a lymph node yield of more than 3 nodes was linked to worse OS (HR 4.337; p = 0.0456) and DFS (HR 3.468; p = 0.0355). This study highlights the high rate of lymph node metastasis in MCC and its detrimental impact on survival, emphasizing the importance of aggressive, guideline-concordant multimodal treatment for improved outcomes.

Merkel Cell Carcinoma With Extensive Bone Marrow Metastasis and Peripheral Blood Involvement: A Case Report With Immunohistochemical and Mutational Studies

Merkel cell carcinoma (MCC) is a rare, highly aggressive skin cancer of neuroendocrine origin that is typically associated with either the presence of Merkel cell polyomavirus or chronic exposure to ultraviolet (UV) light. We report a case of relapsed MCC that presented with new symptoms of fatigue, back pain, and myeloid left shift identified during scheduled follow-up. The patient was found to have circulating neoplastic cells in the peripheral blood and bone marrow metastasis. Immunohistochemistry for synaptophysin, CD56, INSM-1, CK20, CD117 were positive, whereas CD34, TdT, Chromogranin, CD10, myeloperoxidase, CD3 and CD19 were negative. Flow cytometry of the peripheral blood confirmed the presence of an abnormal nonhematopoietic cell population expressing CD56 positivity. A next-generation sequencing (NGS) panel revealed the presence of variants in RB1, TP53, and other genes, some of which have not been previously described in MCC. This rare presentation highlights the challenges in the diagnosis and management of MCC.

SATB2, CKAE1/AE3, and synaptophysin as a sensitive immunohistochemical panel for the detection of lymph node metastases of Merkel cell carcinoma

Histopathological evaluation of lymph nodes in Merkel cell carcinoma has become crucial in progression estimation and treatment modification. This study was undertaken to determine the most sensitive immunohistochemical panel for detecting MCC nodal metastases. We included 56 patients with 102 metastatic MCC lymph nodes, which were tested with seven antibodies: cytokeratin (CKAE1/AE3), CK20, chromogranin A, synaptophysin, INSM1, SATB2, and neurofilament (NF). Tissue microarrays (TMA) composed of 2-mm tissue cores from each nodal metastasis were constructed. A semiquantitative 5-tier scoring system (0%, < 25%, 25-74%, 75-99%, 100% positive MCC cells with moderate to strong reactivity) was implemented. In the statistical assessment, we included Merkel cell polyomavirus (MCPyV) status and expression heterogeneity between lymph nodes from one patient. A cumulative percentage of moderate to strong expression ≥ 75% of tumoral cells was observed for single cell markers as follows: 91/102 (89.2%) SATB2, 85/102 (83%) CKAE1/AE3, 80/102 (78.4%) synaptophysin, 75/102 (75.5%) INSM1, 68/102 (66.7%) chromogranin A, 60/102 cases (58.8%) CK20, and 0/102 (0%) NF. Three markers presented a complete lack of immunoreactivity: 8/102 (7.8%) CK20, 7/102 (6.9%) chromogranin A, and 6/102 (5.9%) NF. All markers showed expression heterogeneity in lymph nodes from one patient; however, the most homogenous was INSM1. The probability of detecting nodal MCC metastases was the highest while using SATB2 as a first-line marker (89.2%) with subsequential adding CKAE1/AE3 (99%); these results were independent of MCPyV status. Synaptophysin showed a superior significance in confirming the neuroendocrine origin of metastatic cells. This comprehensive analysis allows us to recommend simultaneous evaluation of SATB2, CKAE1/AE3, and synaptophysin in the routine pathologic MCC lymph node protocol.

Computational formulation of a multiepitope vaccine unveils an exceptional prophylactic candidate against Merkel cell polyomavirus

Merkel cell carcinoma (MCC) is a rare neuroendocrine skin malignancy caused by human Merkel cell polyomavirus (MCV), leading to the most aggressive skin cancer in humans. MCV has been identified in approximately 43%-100% of MCC cases, contributing to the highly aggressive nature of primary cutaneous carcinoma and leading to a notable mortality rate. Currently, no existing vaccines or drug candidates have shown efficacy in addressing the ailment caused by this specific pathogen. Therefore, this study aimed to design a novel multiepitope vaccine candidate against the virus using integrated immunoinformatics and vaccinomics approaches. Initially, the highest antigenic, immunogenic, and non-allergenic epitopes of cytotoxic T lymphocytes, helper T lymphocytes, and linear B lymphocytes corresponding to the virus whole protein sequences were identified and retrieved for vaccine construction. Subsequently, the selected epitopes were linked with appropriate linkers and added an adjuvant in front of the construct to enhance the immunogenicity of the vaccine candidates. Additionally, molecular docking and dynamics simulations identified strong and stable binding interactions between vaccine candidates and human Toll-like receptor 4. Furthermore, computer-aided immune simulation found the real-life-like immune response of vaccine candidates upon administration to the human body. Finally, codon optimization was conducted on the vaccine candidates to facilitate the in silico cloning of the vaccine into the pET28+(a) cloning vector. In conclusion, the vaccine candidate developed in this study is anticipated to augment the immune response in humans and effectively combat the virus. Nevertheless, it is imperative to conduct in vitro and in vivo assays to evaluate the efficacy of these vaccine candidates thoroughly. These evaluations will provide critical insights into the vaccine's effectiveness and potential for further development.

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.

Conjunctival Merkel cell carcinoma: case report and review of the literature

Merkel cell carcinoma (MCC) of the conjunctiva is rare. We report the case of a 73-year-old man who presented with unilateral foreign body sensation and blurred vision. A rapidly enlarging conjunctival lesion was identified and excised. The histopathological diagnosis was poorly differentiated squamous cell carcinoma, later reclassified as neuroendocrine / Merkel cell carcinoma following excision on subsequent recurrence. The patient developed lymph node and widespread metastatic disease. The challenges of diagnosing MCC at this site are discussed and the literature on treatment options for this aggressive disease is reviewed.

Merkel cell carcinoma

Merkel cell carcinoma (MCC) is a rare neuroendocrine carcinoma. The cellular origin of MCC may include Merkel cell precursors. The incidence of MCC has increased significantly however trends may have been confounded by evolving diagnostic criteria. The two key aetiologies of MCC are ultraviolet radiation and Merkel cell polyoma virus (MCPyV). Both have unique mechanisms of carcinogenesis. MCC presents non-specifically as a rapidly growing, red-to-violet nodule on sun-exposed areas. Diagnostic accuracy has improved through immunohistochemical markers such as CK-20. Lymph nodes should be evaluated in MCC through examination and sentinel biopsy. USS, CT, MRI and CT-PET may be useful in staging. Management depends on tumour location, stage and comorbidities. MCPyV status may guide treatment strategy in the future. Treatment for the primary MCC is commonly wide local excision followed by radiotherapy, guided by anatomical constraints. There is uncertainty about surgical margins. Treatments for nodal disease have not been determined through trials. They include nodal dissection or radiotherapy for clinically or radiologically apparent disease, and adjuvant nodal irradiation for negative nodes, microscopic disease or following nodal dissection for definite disease. Patients with loco-regional advanced inoperable disease should be considered for combination therapy including chemotherapy, radiotherapy, surgery and immunotherapy. Systemic therapy for advanced disease includes immune checkpoint inhibitors targeting the PD-1/PD-L1 pathway. Avelumab can improve survival in metastatic MCC. Immunotherapy may result in longer disease control. Various other immunotherapeutic and molecular agents are undergoing trials. MCC continues to have a high mortality characterized by high recurrence and early metastases.

Surgical Management of Merkel Cell Carcinoma

The incidence of Merkel cell carcinoma (MCC) continues to increase. Understanding of MCC biology has advanced rapidly, with current staging providing valuable prognostic information. MCC treatment often is multidisciplinary. Surgery remains an important component in the staging and treatment, most commonly involving wide excision of the cancer and sentinel lymph node biopsy. Lymphadenectomy is used to treat nodal disease. Radiotherapy enhances locoregional control and possibly survival. Systemic therapies, in particular novel immunotherapies, may be promising in the treatment of advanced or recurrent and metastatic disease.

Clinical Impact of FDG PET/CT of the Lower Extremities in Patients With Merkel Cell Carcinoma With Primary Disease Site Outside of the Lower Extremities

OBJECTIVE. Whole-body imaging extending from the vertex of the head to the toes is considered the standard ¹⁸F-FDG PET/CT protocol for Merkel cell carcinoma, though the evidence establishing this standard is scant. The purpose of this study was to investigate the clinical impact of PET/CT of the lower extremities in patients with Merkel cell carcinoma, a rare aggressive neuroendocrine tumor of the skin. MATERIALS AND METHODS. A total of 101 patients with Merkel cell carcinoma (mean age, 70.9 years) who underwent whole-body PET/CT were included. PET/CT findings in the lower extremities were evaluated on a per-patient basis, and the results were compared between patients with the primary lesion in the lower extremities (lower extremity primary) and those with the primary lesion located between the head and inguinal regions (body primary). Subsequent clinical evaluation and follow-up imaging were used as the reference standard. RESULTS. In the lower extremity (n = 22) and body (n = 79) primary groups, five and eight patients had true metastases in the lower extremities (p = .15). In the body primary group, all metastases in the lower extremities were part of widespread metastases in the body. In contrast, three of five patients (60%) in the lower extremity primary group had isolated metastases in the lower extremities, which differed significantly from the rate in the body primary group (p = .04). Subgroup analysis that included 48 patients who underwent initial staging examinations showed no metastases in the lower extremities regardless of primary location. CONCLUSION. PET/CT of the lower extremities for patients with body primary lesions of Merkel cell carcinoma should be considered of limited clinical utility.

Imaging of Merkel Cell Carcinoma: What Imaging Experts Should Know

Merkel cell carcinoma (MCC) is a rare and aggressive cutaneous neuroendocrine tumor with a higher mortality rate than melanoma. Approximately 40% of MCC patients have nodal or distant metastasis at initial presentation, and one-third of patients will develop distant metastatic disease over their clinical course. Although MCC is rare, its incidence has been steadily increasing. Furthermore, the immunogenicity of MCC and its diagnostic and therapeutic application have made MCC one of the most rapidly developing topics in dermatology and oncology. Owing to the aggressive and complex nature of MCC, a multidisciplinary approach is necessary for management of this tumor, including dermatologists, surgeons, radiation oncologists, medical oncologists, pathologists, radiologists, and nuclear medicine physicians. Imaging plays a crucial role in diagnosis, planning for surgery or radiation therapy, and assessment of treatment response and surveillance. However, MCC is still not well recognized among radiologists and nuclear medicine physicians, likely owing to its rarity. The purpose of this review is to raise awareness of MCC among imaging experts by describing the epidemiology, pathophysiology, and clinical features of MCC and current clinical management with a focus on the role of imaging. The authors highlight imaging findings characteristic of MCC, as well as the clinical significance of CT, MRI, sentinel lymph node mapping, fluorine 18 fluorodeoxyglucose PET/CT, and other nuclear medicine studies such as bone scintigraphy and somatostatin receptor scintigraphy. ^©RSNA, 2019.

A Report of 13 Cases of Merkel Cell Carcinoma: Single-Center Experience and Review of the Literature

Background

There is limited data knowledge of Merkel cell carcinoma (MCC) in Turkey aside from a few case reports.

Objective

The aim of this study was to describe the clinical characteristics, demographic features, therapeutic parameters, and outcome of primary cutaneous MCC cases from Turkey.

Methods

Digital medical records of the 13 MCC patients who were followed-up at a tertiary referral center were retrospectively analyzed. Clinic, demographic, tumor characteristics, and survival of the patients were retrieved.

Results

Most of our patients were elderly. Female predominance was noticed. The most common primary site of the tumors was the lower extremities. The overall survival was 42 months, 68% at first year, 68% at third years, and 29% at fifth years.

Conclusion

This is the first largest report from Turkish population with female predominance, and lower extremity tendency.

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.

Merkel cell polyomavirus and Merkel cell carcinoma

Merkel cell polyomavirus (MCPyV) causes the highly aggressive and relatively rare skin cancer known as Merkel cell carcinoma (MCC). MCPyV also causes a lifelong yet relatively innocuous infection and is one of 14 distinct human polyomaviruses species. Although polyomaviruses typically do not cause illness in healthy individuals, several can cause catastrophic diseases in immunocompromised hosts. MCPyV is the only polyomavirus clearly associated with human cancer. How MCPyV causes MCC and what oncogenic events must transpire to enable this virus to cause MCC is the focus of this essay.This article is part of the themed issue 'Human oncogenic viruses'.

PD-L1 inhibition with avelumab for metastatic Merkel cell carcinoma

INTRODUCTION

Merkel cell carcinoma (MCC) is a rare and aggressive neuroendocrine skin cancer that lacks durable responses to traditional chemotherapy. Areas covered: After MCC was shown to be an immunogenic tumor, small trials revealed high objective response rates to PD-1/PD-L1 checkpoint inhibitors. The JAVELIN Merkel 200 (NCT02155647) trial tested the use of avelumab, a human IgG1 monoclonal antibody against PD-L1, in metastatic MCC. Avelumab recently became the first approved drug for metastatic MCC. Expert commentary: By conducting broad phase I studies assessing the safety of avelumab and a small phase II study demonstrating efficacy in this rare orphan tumor type, avelumab gained accelerated approval for the treatment of metastatic MCC. Additional studies are needed to determine how the antibody-dependent cellular cytotoxicity (ADCC) competent Fc region of avelumab contributes to disease control. Remaining questions: Longer follow-up will determine the durability of checkpoint blockade in controlling metastatic MCC. Additional studies will assess the utility and safety of adjuvant checkpoint blockade in patients with excised MCC. How to increase response rates by combining PD-1/PD-L1 blockade with other treatment approaches needs to be explored. In addition, treatment options for MCC patients who fail or do not respond to avelumab need to be identified.

Update on Merkel Cell Carcinoma

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

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.

Reduced H3K27me3 expression in Merkel cell polyoma virus-positive tumors

Merkel cell carcinoma is a primary cutaneous neuroendocrine carcinoma, which once metastatic is difficult to treat. Recent mutation analyses of Merkel cell carcinoma revealed a low number of mutations in Merkel cell polyomavirus-associated tumors, and a high number of mutations in virus-negative combined squamous cell and neuroendocrine carcinomas of chronically sun-damaged skin. We speculated that the paucity of mutations in virus-positive Merkel cell carcinoma may reflect a pathomechanism that depends on derangements of chromatin without alterations in the DNA sequence (epigenetic dysregulation). One central epigenetic regulator is the Polycomb repressive complex 2 (PRC2), which silences genomic regions by trimethylating (me3) lysine (K) 27 of histone H3, and thereby establishes the histone mark H3K27me3. Recent experimental research data demonstrated that PRC2 loss in mice skin results in the formation of Merkel cells. Prompted by these findings, we explored a possible contribution of PRC2 loss in human Merkel cell carcinoma. We examined the immunohistochemical expression of H3K27me3 in 35 Merkel cell carcinomas with pure histological features (22 primary and 13 metastatic lesions) and in 5 combined squamous and neuroendocrine carcinomas of the skin. We found a strong reduction of H3K27me3 staining in tumors with pure histologic features and virus-positive Merkel cell carcinomas. Combined neuroendocrine carcinomas had no or only minimal loss of H3K27me3 labeling. Our findings suggest that a PRC2-mediated epigenetic deregulation may play a role in the pathogenesis of virus-positive Merkel cell carcinomas and in tumors with pure histologic features.

Merkel Cell Polyomavirus Small T Antigen Initiates Merkel Cell Carcinoma-like Tumor Development in Mice

Merkel cell carcinoma (MCC) tumor cells express several markers detected in normal Merkel cells, a nonproliferative population of neuroendocrine cells that arise from epidermis. MCCs frequently contain Merkel cell polyomavirus (MCPyV) DNA and express viral transforming antigens, sT and tLT, but the role of these putative oncogenes in MCC development, and this tumor's cell of origin, are unknown. Using a panel of preterm transgenic mice, we show that epidermis-targeted coexpression of sT and the cell fate-determinant atonal bHLH transcription factor 1 (ATOH1) leads to development of widespread cellular aggregates, with histology and marker expression mimicking that of human intraepidermal MCC. The MCC-like tumor phenotype was dependent on the FBXW7-binding domain of sT, but not the sT-PP2A binding domain. Coexpression of MCPyV tLT did not appreciably alter the phenotype driven by either sT or sT combined with ATOH1. MCPyV sT, when coexpressed with ATOH1, is thus sufficient to initiate development of epidermis-derived MCC-like tumors in mice. Cancer Res; 77(12); 3151-7. ©2017 AACR.

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

PURPOSE OF REVIEW

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

RECENT FINDINGS

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

SUMMARY

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

Merkel cell carcinoma: Epidemiology, prognosis, therapy and unmet medical needs

Merkel cell carcinoma (MCC) is a rare skin cancer that is associated with Merkel cell polyomavirus infection in most cases. Incidence rates of MCC have increased in past decades. Risk factors for MCC include ultraviolet light exposure, immunosuppression and advanced age. MCC is an aggressive malignancy with frequent recurrences and a high mortality rate, although patient outcomes are generally more favourable if the patient is referred for treatment at an early stage. Although advances have been made recently in the MCC field, large gaps remain with regard to definitive biomarkers and prognostic indicators. Although MCC is chemosensitive, responses in advanced stages are mostly of short duration, and the associated clinical benefit on overall survival is unclear. Recent nonrandomised phase 2 clinical trials with anti-PD-L1/PD-1 antibodies have demonstrated safety and efficacy; however, there are still no approved treatments for patients with metastatic MCC. Patients with advanced disease are encouraged to participate in clinical trials for treatment, indicating the largely unmet need for durable, safe treatment within this population.

Analysis of Prognostic Factors from 9387 Merkel Cell Carcinoma Cases Forms the Basis for the New 8th Edition AJCC Staging System

BACKGROUND

The first consensus Merkel cell carcinoma (MCC) staging system was published in 2010. New information on the clinical course prompts review of MCC staging.

METHODS

A total of 9387 MCC cases from the National Cancer Data Base Participant User File with follow-up and staging data (1998-2012) were analyzed. Prognostic differences based on clinical and pathological staging were evaluated. Survival estimates were compared by disease extent.

RESULTS

Sixty-five percent of cases presented with local disease, whereas 26 and 8 % presented with nodal and distant disease. Disease extent at presentation was predictive of 5-year overall survival (OS) with estimates of 51, 35, and 14 % for local, nodal, and distant disease. Tumor burden at the regional nodal basin was predictive of 5-year OS with estimates of 40 and 27 % for clinically occult and clinically detected nodal disease. For local disease, we confirm improved prognosis when the regional nodal basin was negative by pathological compared with clinical staging. We identified 336 cases with clinically detected nodal disease and unknown primary tumor and showed improved prognosis over cases presenting with concurrent primary tumor (OS estimates of 42 vs. 27 %).

CONCLUSIONS

Analysis of a national dataset of MCC cases validates the predictive value of disease extent at presentation. Separation of clinical and pathological stage groups and regrouping of unknown primary tumors are supported by the analysis. The revised staging system provides more accurate prognostication and has been formally accepted by the AJCC staging committee for inclusion in the 8th edition.

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.

Histological pattern of Merkel cell carcinoma sentinel lymph node metastasis improves stratification of Stage III patients

Sentinel lymph node biopsy is used to stage Merkel cell carcinoma, but its prognostic value has been questioned. Furthermore, predictors of outcome in sentinel lymph node positive Merkel cell carcinoma patients are poorly defined. In breast carcinoma, isolated immunohistochemically positive tumor cells have no impact, but in melanoma they are considered significant. The significance of sentinel lymph node metastasis tumor burden (including isolated tumor cells) and pattern of involvement in Merkel cell carcinoma are unknown. In this study, 64 Merkel cell carcinomas involving sentinel lymph nodes and corresponding immunohistochemical stains were reviewed and clinicopathological predictors of outcome were sought. Five metastatic patterns were identified: (1) sheet-like (n=38, 59%); (2) non-solid parafollicular (n=4, 6%); (3) sinusoidal, (n=11, 17%); (4) perivascular hilar (n=1, 2%); and (5) rare scattered parenchymal cells (n=10, 16%). At the time of follow-up, 30/63 (48%) patients had died with 21 (33%) attributable to Merkel cell carcinoma. Patients with pattern 1 metastases had poorer overall survival compared with patients with patterns 2-5 metastases (P=0.03), with 22/30 (73%) deaths occurring in pattern 1 patients. Three (10%) deaths occurred in patients showing pattern 5, all of whom were immunosuppressed. Four (13%) deaths occurred in pattern 3 patients and 1 (3%) death occurred in a pattern 2 patient. In multivariable analysis, the number of positive sentinel lymph nodes (1 or 2 versus >2, P<0.0001), age (<70 versus ≥70, P=0.01), sentinel lymph node metastasis pattern (patterns 2-5 versus 1, P=0.02), and immune status (immunocompetent versus suppressed, P=0.03) were independent predictors of outcome, and could be used to stratify Stage III patients into three groups with markedly different outcomes. In Merkel cell carcinoma, the pattern of sentinel lymph node involvement provides important prognostic information and utilizing this data with other clinicopathological features facilitates risk stratification of Merkel cell carcinoma patients who may have management implications.

Merkel cell carcinoma: Do you know your guidelines?

BACKGROUND

Merkel cell carcinoma (MCC) is a cutaneous neuroendocrine malignancy that exhibits clinically aggressive features and is associated with a poor prognosis. The incidence of MCC seems to be increasing for reasons unknown, and is estimated to be 0.32/100,000 in the United States.

METHODS

This article will review the current literature and National Comprehensive Cancer Network practice guidelines in the treatment of MCC.

RESULTS

Resection of MCC with negative margins remains the mainstay of therapy. Positive nodal disease should be treated with neck dissection and adjuvant radiotherapy. High-risk patients should undergo adjuvant radiotherapy, which improves oncologic outcomes. The role of chemotherapy is less clear and is currently reserved for advanced-stage MCC and palliative therapy.

CONCLUSION

The pathogenesis of MCC has recently been impacted with the discovery of the Merkel cell polyomavirus (MCPyV). Research to establish targeted and immunologic therapeutic options are ongoing.

Merkel cell carcinoma of the head and neck: pathogenesis, current and emerging treatment options

Merkel cell carcinoma (MCC) is a relatively uncommon, neuroendocrine, cutaneous malignancy that often exhibits clinically aggressive features and is associated with a poor prognosis. It typically presents as a painless, rapidly enlarging, dome-shaped red or purplish nodule in a sun-exposed area of the head and neck or upper extremities. Our understanding of MCC has increased dramatically over the last several years and the pathogenesis continues to be an area of active research. The etiology is likely multifactorial with immunosuppression, UV-induced skin damage, and viral factors contributing to the development of MCC. The recent discovery of Merkel cell polyomavirus has allowed for at least one aspect of disease development to be much better understood. In most cases, treatment consists of wide local excision with adjuvant radiation therapy. The role of chemotherapeutics is still being defined. The recent advancement of knowledge regarding the pathogenesis of MCC has led to an explosion research into novel therapeutic agents and strategies. This review seeks to summarize the current body of literature regarding the pathogenesis of MCC and potential targets for future therapies.