Merkel cell carcinoma: a review and update on aetiopathogenesis, diagnosis and treatment approaches

Updates on the diagnosis, current and future therapeutic options in Merkel-cell carcinoma

Merkel-cell carcinoma (MCC) is a rare and extremely aggressive nonmelanocytic cutaneous neuroendocrine carcinoma. Historically, it has been associated with limited therapy options and poor prognosis. While its incidence has been rising over the last two decades, recent discoveries and a better understanding of its pathogenesis, viral association and immunologic features have allowed for the emergence of new therapies. Surgical excision with or without radiotherapy remains the first-line therapy for primary lesions without evidence of metastatic disease. The majority of MCC cases are regrettably diagnosed at advanced stages and oftentimes require systemic therapy. There have been several significant advances in the treatment of MCC in the last decade. Among these have been the development of immune checkpoint inhibitors targeting the programmed death protein-1 (PD-1)/programmed death ligand-1 (PDL-1). Despite recent success of immunotherapy, nearly 50% of patients diagnosed with MCC still succumb to the disease. Fortunately, there has been a number of new targeted therapies that hold great promise. Among them are phosphatidylinositide-3kinase (Pl3K) inhibitors, adoptive T-cell immunotherapy, activated NK-92 cells infusions and therapeutic vaccines. Additional emerging therapeutic targets include cellular ubiquitin-specific processing protease 7 (Usp7) that restricts viral replication and IFN genes (STING), activation of which promotes an antitumor inflammatory response.

Comparative In Vitro and In Vivo Studies on Feline, Canine, and Human Merkel Cell Carcinoma

Merkel cell carcinoma (MCC) is an aggressive cutaneous neuroendocrine tumor, and most human MCC cases are infected by Merkel cell polyomavirus (MCPyV). However, the underlying pathogeneses of MCC in animals remain unclear. In the present study, newly established cell lines from feline and canine MCC, a MCPyV-positive human MCC cell line, and MCC tissues from 25 cats and 1 dog were examined and compared pathologically. Feline and canine MCCs were composed of tumor cells arranged in trabeculae and solid packets. Twenty out of 25 feline MCC cases (80%) had other proliferative cutaneous lesions, such as carcinoma in situ and squamous cell carcinoma. Among the 25 feline MCC cases, tumor cells were immunopositive for cytokeratins (CKs), including CK5/6 (4/25 cases, 16%), CK7 (5, 20%), CK18 (25, 100%), CK19 (20, 80%), and CK20 (20, 80%). The tumor cells of feline MCC were also immunopositive for synaptophysin (24/25, 96%) and CD56 (22/25, 88%). The tumor cells of canine MCC were immunopositive for CK18, CK19, CK20, and synaptophysin. Cultured feline and canine MCC cells grew in adherent monolayers and exhibited diffuse cytoplasmic immunoreactivity for CKs, whereas human MCC cells grew in suspension and exhibited dot-like cytoplasmic immunoreactivity for CKs. Differences in the distribution of CKs between human and animal MCC may be attributed to cell adhesion propensities. MCPyV genes and antigen were not detected in feline or canine MCC, suggesting a different etiology from human MCC.

Radiotherapy for inoperable Merkel cell carcinoma: a systematic review and pooled analysis

Background

Cumulative data on radiation monotherapy for Merkel cell carcinoma (MCC) is lacking.

Objective

We sought to synthesize all available data on treatment outcomes for radiation monotherapy for inoperable stage I-III MCC.

Methods

We performed a systematic review of the current literature. Articles published in English in the PubMed database up to July 29, 2016, were evaluated.

Results

Eight case reports, 4 case series, and 6 retrospective studies, yielding 68 patients, were included in our analysis. Of the 24 stage I/II patients treated with local irradiation, 6 (25%) relapsed and 1 (4%) died from MCC. Of the 24 stage I/II patients treated with local and regional nodal irradiation, 5 (21%) relapsed and 2 (8%) died from MCC. Of the 20 stage III patients treated with local and regional nodal irradiation, 12 (60%) relapsed and 7 (35%) died from MCC.

Conclusions

Radiation monotherapy appears to be a reasonable treatment modality for patients with inoperable stage I-III MCC. Further investigation with prospective studies is needed to draw definitive conclusions.

Aberrant expression of ALK and EZH2 in Merkel cell carcinoma

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Dramatic Increase in the Incidence and Mortality from Merkel Cell Carcinoma in the United States

Merkel cell carcinoma is a cutaneous neuroendocrine neoplasm that has been poorly studied in contemporary cohorts. Patients with Merkel cell carcinoma from 1986 to 2011 were identified in the Surveillance Epidemiology and End Results registry. A total of 5211 patients met the inclusion criteria. The mean age was 74.9 years; majority were male (61.4%) and white (94.9%). Patients were divided into two cohorts: Group 1 (1986 and 1999) and Group 2 (1999-2010). Group 2 was more likely to have Stage III disease (14.6 vs 23.3%, P < 0.001) and less likely to have Stage I/II disease (71.8 vs 65.1%, P < 0.0001). The increase in Stage III was likely secondary to increased use of sentinel lymph node biopsy. Disease-specific five-year survival for Stages I/II was 78.1 per cent and Stage III was 54 per cent. Disease-specific five-year survival was unchanged between Groups 1 and 2, 69.9 versus 66.6 per cent, respectively (P = 0.44). Both incidence and mortality significantly increased over the study period with P value for both trends <0.0001. In 1986, incidence and mortality rates per 100,000 were 0.22 and 0.03, respectively, and increased to 0.79 and 0.43 in 2011, respectively. There has been a greater than 333 per cent increase in mortality from Merkel cell carcinoma.

Merkel cell carcinoma of the lower leg with retroperitoneal GIST: a very rare association

Merkel cell carcinoma (MCC) is a rare neuroendocrine tumor of the skin. Although its association with other malignancies is well known, an association with gastrointestinal stromal tumor (GIST) has yet not been described.We report about a 65-year-old female patient who presented with a hypervascularized subcutaneous tumor mass of her left calf. Resection of the primary tumor and histopathological investigations confirmed the diagnosis of MCC. The patient was treated by delayed Mohs surgery, and tumor-free margins were obtained. Sentinel lymph node biopsy was negative for metastatic spread. Primary tumor and lymph node basin were treated by adjuvant radiotherapy. During staging of the patient, a second malignancy-a GIST-was detected. Neoadjuvant treatment with multikinase inhibitor imatinib induced a partial response of GIST that was eventually removed by surgery. However, 8 months later, the patient developed subcutaneous regional metastases of MCC, which were surgically removed. Adjuvant therapy was planned by oncologists.To the best of our knowledge, the occurrence of MCC and GIST in the same patient has yet not been reported. In contrast to GIST, MCC did not respond to imatinib, although c-kit mutations are common in MCC.

Vulvar cancer: a review for dermatologists

Vulvar malignancies are important tumors of the female reproductive system. They represent a serious health issue with an incidence between 2 and 7 per 100,000 and year. We provide a review about most important cancer entities, i.e., melanoma, squamous cell carcinoma, basal cell carcinoma, neuroendocrine cancer, and skin adnexal malignancies.Squamous cell carcinoma is the most common vulvar malignancy that can develop from vulvar intraepithelial neoplasia or de novo. Basal cell carcinoma represents only 2% of all vulvar cancers. Melanoma of the vulva exists in two major types-superficial spreading and acral lentiginous. A special feature is the occurrence of multiple vulvar melanomas. Of the adnexal cancer types Paget's disease and carcinoma are seen more frequently than other adnexal malignancies. The dermatologist should be aware of this problem, since he might be the first to be consulted by patients for vulvar disease. Treatment should be interdisciplinary in close association to gynecologists, oncologists, and radiologists.

miRNA-34a underexpressed in Merkel cell polyomavirus-negative Merkel cell carcinoma

Merkel cell polyomavirus (MCV) is frequently detectable in Merkel cell carcinoma (MCC) tumors, but the significance of MCV infection is not yet totally understood. Thus far, no key regulatory miRNA has been identified for MCC tumorigenesis. However, distinct miRNA expression profiles have been suggested for MCV-positive and MCV-negative tumors. We used microarray hybridization to identify miRNA expression differences in MCC tumor samples according to MCV status and further validated these results by quantitative reverse transcription polymerase chain reaction (qRT-PCR). When compared with MCV-negative tumors, we detected overexpression of miR-34a, miR-30a, miR-142-3p, and miR-1539 in those MCV positives. In addition, slight underexpression was detectable in MCV-positive tumors of miR-181d. We confirmed the distinct expression of miRNAs in MCV-positive and MCV-negative tumors and confirmed statistically significant underexpression of miR-34a in MCV-negative tumors by both array analysis and qRT-PCR. Neither tumor location nor development of metastases affected miRNA expression.

Risk of second cancers in merkel cell carcinoma: a meta-analysis of population based cohort studies

The risk of second cancers in Merkel cell carcinoma (MCC) remains uncertain since risk estimates vary worldwide. The global MCC population is growing and there is a demand for better knowledge of prognosis of this disease. The Cochrane Database of Systematic Reviews, MEDLINE, and EMBASE search engines were searched for the relevant literature between January 1999 and September 2014 by use of explicit search criteria. The main outcome was second malignancies associated with MCC patients measured by standardized incidence ratios (SIRs) or other estimates of risks. Five papers fulfilled the inclusion criteria and reported SIRs of second cancer in MCC which varied from 1.07 to 2.80. Performing meta-analysis using random effects model revealed that there was an increased risk for second malignancies due to MCC (SIR, 1.52; 95% CI, 1.10–2.11). There was a significant increase in risk for malignant melanoma (SIR, 3.09; 95% CI, 2.02–4.73) as compared to all common second malignancies among the studies. Updated knowledge about risk of second malignancies in MCC will help in better assessment of the disease prognosis and will help in optimizing the medical and surgical treatment, radiotherapy, follow-up, and surveillance procedures.

Update of cetuximab for non-melanoma skin cancer

INTRODUCTION

Non-melanoma skin cancer (NMSC) has become the most common malignancy in humans. Targeted therapies are recent developments for these tumors. Monoclonal antibody cetuximab has proven its efficacy and has improved tolerability compared to classical chemotherapy protocols, and this prompted us to analyze new data on the use of cetuximab in cutaneous NMSC.

AREAS COVERED

The monoclonal antibody cetuximab against epidermal growth factor receptor (EGFR) has been investigated for its use in NMSC during the years between 2011 and 2013. A PUBMED research 2011 - 2013 has been conducted using the following terms: 'Non-melanoma skin cancer AND cetuximab', 'cutaneous squamous cell carcinoma AND cetuximab', and 'basal cell carcinoma AND cetuximab' and 'cetuximab AND skin toxicity'. Available data were analyzed - irrespective of their level of evidence, that is, case reports and case series were included.

EXPERT OPINION

Current evidence of cetuximab's efficacy in NMSC was mainly obtained in cutaneous squamous cell carcinoma (SCC) and to a lesser extent in basal cell carcinoma (BCC). Response rates vary for neoadjuvant, adjuvant, monotherapy and combined therapy with cetuximab. Limitations are the low number of patients treated (33 patients with SCC, 4 patients with BCC) and the low quality of studies reported. Management of cutaneous toxicities of EGFR inhibitors is necessary, and guidelines are available. Proactive therapy might also prevent skin toxicity of higher grades, with EGFR inhibitor cetuximab as an option for recurrent or advanced NMSC of the skin. It seems to be justified particularly in very high risk epithelial tumors. There is an urgent need for Phase III trials. In the future, combined drug therapy with other monoclonal antibodies and/or radiotherapy may further improve efficacy and response rates for NMSC.