p63 expression as a new prognostic marker in Merkel cell carcinoma

Current status of Merkel cell carcinoma: Epidemiology, pathogenesis and prognostic factors

Merkel cell carcinoma (MCC) is an extremely rare cutaneous neuroendocrine cancer, with an incidence approximately 40 times lower than that of malignant melanoma; however, its significantly inferior survival rate compared to melanoma establishes MCC as the most lethal form of skin cancer. In recent years, a substantial body of literature has demonstrated a gradual increase in the incidence of MCC. Although the two factors that contribute to MCC, ultraviolet radiation and Merkel cell polyomavirus infection, have been well established, the specific pathogenesis of this disease remains unclear. Additionally, considering the high lethality and recurrence rates of MCC, as well as the absence of specific antitumor drugs, it is crucial to elucidate the factors that can accurately predict patients' outcomes. In this review, we summarized the significant advancements in the epidemiological characteristics, pathogenesis, and the factors that influence patient prognosis of MCC to enhance clinical practices and public health efforts.

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

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

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Merkel cell carcinoma: an update

Merkel cell carcinoma (MCC) is an uncommon primary cutaneous neuroendocrine carcinoma associated with an adverse prognosis. In recent years, our understanding of MCC biology has markedly progressed. Since the discovery of the Merkel cell polyomavirus, it has become clear that MCC represents an ontogenetically dichotomous group of neoplasms with overlapping histopathology. Specifically, most MCCs arise secondary to viral oncogenesis, while a smaller subset is the direct result of UV-associated mutations. The distinction of these groups bears relevance in their immunohistochemical and molecular characterization, as well as in disease prognosis. Further recent developments relate to the landmark utilization of immunotherapeutics in MCC, providing optimistic options for the management of this aggressive disease. In this review, we discuss both fundamental and emerging concepts in MCC, with a particular focus on topics of practical relevance to the surgical or dermatopathologist.

MicroRNA dysregulations in Merkel cell carcinoma: Molecular mechanisms and clinical applications

Merkel cell carcinoma (MCC) is an aggressive skin malignancy with two distinct etiologies. The first, which accounts for the highest proportion, is caused by Merkel cell polyomavirus (MCPyV), a DNA tumor virus. A second, UV-induced, MCC form has also been identified. Few MCC diagnostic, prognostic, and therapeutic options are available. MicroRNAs (miRNAs) are small noncoding RNA molecules, which play a key role in regulating various physiologic cellular functions including cell cycling, proliferation, differentiation, and apoptosis. Numerous miRNAs are dysregulated in cancer, by acting as either tumor suppressors or oncomiRs. The aim of this review is to collect, summarize, and discuss recent findings on miRNAs whose dysregulation has been assumed to play a role in MCC. The potential clinical application of miRNAs as diagnostic and prognostic biomarkers in MCC is also described. In the future, miRNAs will potentially gain clinical significance for the improvement of MCC diagnostic, prognostic, and therapeutic options.

T-Cell Mediated Immunity in Merkel Cell Carcinoma

Merkel cell carcinoma (MCC) is a rare and frequently lethal skin cancer with neuroendocrine characteristics. MCC can originate from either the presence of MCC polyomavirus (MCPyV) DNA or chronic ultraviolet (UV) exposure that can cause DNA mutations. MCC is predominant in sun-exposed regions of the body and can metastasize to regional lymph nodes, liver, lungs, bone, and brain. Older, light-skinned individuals with a history of significant sun exposure are at the highest risk. Previous studies have shown that tumors containing a high number of tumor-infiltrating T-cells have favorable survival, even in the absence of MCPyV DNA, suggesting that MCPyV infection enhances T-cell infiltration. However, other factors may also play a role in the host antitumor response. Herein, we review the impact of tumor infiltrating lymphocytes (TILs), mainly the CD4⁺, CD8⁺, and regulatory T-cell (Tregs) responses on the course of MCC, including their role in initiating MCPyV-specific immune responses. Furthermore, potential research avenues related to T-cell biology in MCC, as well as relevant immunotherapies are discussed.

Large Cell Neuroendocrine Carcinoma of the Skin/Conjunctiva: A Series of 6 Cases including 1 Combined Case With Squamous Cell Carcinoma

ABSTRACT

This study sought to reveal the clinicopathologic characteristics of large cell neuroendocrine carcinoma (LCNEC) of the skin/conjunctiva. The retrieved patients included 3 men and 3 women with a median age of 85 (63-95) years. All lesions occurred on the face, including the ears, with a median tumor size of 11.5 (7-65) mm. Lymph node metastasis was observed in 5 (83%) of 6 cases, and distant metastasis was noted in 2 (33%). One patient (17%) who had a 13-mm-sized tumor died of the tumor 13 months after excision. All tumors were mainly located in the dermis, and one of them also exhibited intraepithelial spreading. The cytology resembled that of an LCNEC in other organs. No adnexal differentiation was observed. Five cases were of the pure type, but one had a component of squamous cell carcinoma. Immunoreactivities for CAM5.2, CK7, CK19, BerEP4, epithelial membrane antigen, neuron-specific enolase, synaptophysin, c-KIT, GATA3, and bcl-2 were frequently present, but CK20, neurofilament, Merkel cell polyomavirus large T antigen, mammaglobin, estrogen receptor, HER2, and TTF1 were completely negative in all cases. Mutant-pattern immunostaining of p53, PTEN, and Rb was frequently observed. The Ki67 rate exceeded 70% in all cases. LCNEC of the skin/conjunctiva is a morphologically-defined group of primary cutaneous/conjunctival neuroendocrine neoplasm, although it may be heterogeneous similar to other-site LCNEC or Merkel cell carcinoma. This study highlighted the predominant location for the face, high metastatic and lethal potential, possible combination with other tumor components, and frequent mutant-type immunoexpressions of p53, PTEN, and Rb in this tumor group.

Intron 4-5 hTERT DNA Hypermethylation in Merkel Cell Carcinoma: Frequency, Association with Other Clinico-pathological Features and Prognostic Relevance

Merkel cell carcinoma (MCC) is an aggressive skin tumor with neuroendocrine differentiation, mainly affecting elderly population or immunocompromised individuals. As methylation of the human telomerase reverse transcriptase (mhTERT) has been shown to be a prognostic factor in different tumors, we investigated its role in MCC, in particular in intron 4-5 where rs10069690 has been mapped and recognized as a cancer susceptibility locus. DNA methylation analysis of hTERT gene was assessed retrospectively in a cohort of 69 MCC patients from the University of Bologna, University of Turin and University of Insubria. Overall mortality was evaluated with Kaplan-Meier curves and multivariable Royston-Parmar models. High levels of mhTERT (mhTERT_high) (HR = 2.500, p = 0.015) and p63 (HR = 2.659, p = 0.016) were the only two clinico-pathological features significantly associated with a higher overall mortality at the multivariate analysis. We did not find different levels of mhTERT between MCPyV (+) and (-) cases (21 vs 14, p = 0.554); furthermore, mhTERT_high was strongly associated with older age (80.5 vs 72 years, p = 0.026), no angioinvasion (40.7% vs 71.0%, p = 0.015), lower Ki67 (50 vs 70%, p = 0.005), and PD-L1 expressions in both tumor (0 vs 3%, p = 0.021) and immune cells (0 vs 10%, p = 0.002). mhTERT is a frequently involved epigenetic mechanism and a relevant prognostic factor in MCC. In addition, it belongs to the shared oncogenic pathways of MCC (MCPyV and UV-radiations) and it could be crucial, together with other epigenetic and genetic mechanisms as gene amplification, in determining the final levels of hTERT mRNA and telomerase activity in these patients.

Relationship between p63 and p53 expression in Merkel cell carcinoma and corresponding abnormalities in TP63 and TP53: a study and a proposal

Merkel cell carcinoma (MCC) is a rare, aggressive cutaneous neuroendocrine carcinoma. Oncogenesis occurs via Merkel cell polyomavirus-mediated (MCPyV+) and/or ultraviolet radiation-associated (MCPyV-) pathways. Advanced clinical stage and an MCPyV- status are important adverse prognostic indicators. There is mounting evidence that p63 expression is a negative prognostic indicator in MCC and that it correlates with MCPyV- status. p63 is a member of the p53 family of proteins among which complex interactions occur. It has two main isoforms (proapoptotic TAp63 and oncogenic ΔNp63). Paradoxically, TAp63 predominates in MCC. To explore this quandary, we examined relationships between p63 and p53 expression and corresponding abnormalities in the TP63 and TP53 genes in MCC. A cohort of 26 MCCs (12 MCPyV+ and 14 MCPyV-) was studied. Comparative immunohistochemical expression of p63 and p53 was evaluated semiquantitatively (H scores) and qualitatively (aberrant patterns). The results were compared with genetic abnormalities in TP63 and TP53 via next-generation sequencing. p63 was positive in 73% of cases. p53 showed "wild-type" expression in 69%, with "aberrant" staining in 31%. TP63 mutations (predominantly low-level copy gains; 23% of cases) and mainly pathogenic mutations in TP53 (50% of cases) featured in the MCPyV- subset of cases. p63 expression correlated quantitatively with p53 expression and qualitatively with aberrant patterns of the latter. Increased expression of p63 and p53 and aberrant p53 staining correlated best with TP53 mutation. We propose that p63 expression (ie, proapoptotic TAp63) in MCC is most likely functionally driven as a compensatory response to defective p53 tumor suppressor activity.

Merkel cell carcinoma: A review

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

Exploring the Prognostic Role of Ki67 Proliferative Index in Merkel Cell Carcinoma of the Skin: Clinico-Pathologic Analysis of 84 Cases and Review of the Literature

The exact prediction of outcome of patients with Merkel cell carcinoma (MCC) of the skin is difficult to determine, although several attempts have been made to identify clinico-pathologic prognostic factors. The Ki67 proliferative index is a well-known marker routinely used to define the prognosis of patients with neuroendocrine neoplasms. However, its prognostic value has been poorly investigated in MCC, and available published results are often contradictory mainly because restricted to small series in the absence of standardized methods for Ki67 evaluation. For this reason, we explored the potential prognostic role of Ki67 proliferative index in a large series of MCCs using the WHO standardized method of counting positive cells in at least 500 tumor cells in hot spot areas on camera-captured printed images. In addition, since MCC may be considered as the cutaneous counterpart of digestive neuroendocrine carcinomas (NECs), we decided to stratify MCCs using the available and efficient Ki67 threshold of 55%, which was found prognostic in digestive NECs. This choice was also supported by the Youden index analysis. In addition, we analyzed the prognostic value of other clinico-pathologic parameters using both univariate and multivariate analysis. Ki67 index appeared significantly associated with prognosis at univariate analysis together with stage IV, lack of MCPyV, and p63 expression, but not at the multivariate analysis, where survival resulted independently influenced by p63 expression and tumor stage, only.

Merkel Cell Polyomavirus and Merkel Cell Carcinoma

Viruses are the cause of approximately 15% of all human cancers. Both RNA and DNA human tumor viruses have been identified, with Merkel cell polyomavirus being the most recent one to be linked to cancer. This virus is associated with about 80% of Merkel cell carcinomas, a rare, but aggressive cutaneous malignancy. Despite its name, the cells of origin of this tumor may not be Merkel cells. This review provides an update on the structure and life cycle, cell tropism and epidemiology of the virus and its oncogenic properties. Putative strategies to prevent viral infection or treat virus-positive Merkel cell carcinoma patients are discussed.

Prognostic Impact of MCPyV and TIL Subtyping in Merkel Cell Carcinoma: Evidence from a Large European Cohort of 95 Patients

Merkel cell carcinoma is a rare (∼ 2000 cases/year in the USA) but aggressive neuroendocrine neoplasm of the skin. In 2008, the Merkel cell polyomavirus (MCPyV) was found to be clonally integrated in approximately 80% of Merkel cell carcinomas. The remaining 20% have large numbers of UV-associated mutations. Importantly, both the UV-induced neoantigens in virus-negative Merkel cell carcinoma and the Merkel cell polyomavirus oncogenes that are required for virus-positive tumor growth are highly immunogenic. Indeed, antigen-specific T cells detected in patients are frequently "dysfunctional/exhausted," and the inhibitory ligand PD-L1 is often expressed by Merkel cell carcinoma cells. These data led to point our attention on the quantity and the quality of the immune response in Merkel cell carcinoma. Here, we found CD8+ lymphocytes are the only singly evaluated lymphocyte subclass that strongly influenced overall survival and disease-specific survival in Merkel cell carcinoma. In addition, we highlighted as Merkel cell polyomavirus is a strong prognostic factor and as it prompts a host immune response involving various lymphocyte subclasses (CD3, CD8, FoxP3, and PD-L1 positive) in MCC. For this reason, we proposed a novel eye-based "immunoscore" model, obtained by tumor infiltrating lymphocytes subtyping (CD3, CD8, FoxP3, and PD-L1) that could provide additional prognostic information in Merkel cell carcinoma.

p63 expression in Merkel cell carcinoma: comparative immunohistochemistry invokes TAp63 as the dominant isoform involved

The literature suggests that p63 expression in Merkel cell carcinoma (MCC) is associated with a poor prognosis. p63 immunohistochemistry marks the 2 main isoforms of this transcriptional protein: TAp63 (tumor suppressor-like properties) and ∆Np63 (oncogenic properties). Little information about the isoform of relevance in MCC exists. p40 immunohistochemistry specifically marks ∆Np63, and using comparative, semiquantitative expression of p63 and p40, we sought to clarify the issue. Our cohort of 53 cases (28 men and 25 women, median age 79 years, interquartile range 71-88) was stratified by morphology and viral status. Immunohistochemistry (p63, p40, and cytokeratin 5/6) was performed, H-scores for nuclear expression of p63 and p40 were derived (2 observers; positivity ≥ 10), and interobserver agreement was evaluated. Clinical, pathological, and outcome data were documented. The results were analyzed statistically. Mortality amounted to 57% (median follow-up 686 days, interquartile range 292-1599). Positivity for Merkel cell polyomavirus was observed in 29 (55%) of cases. Expression of p63 and p40 was present in 36 (69%) and 4 (8%) of cases, respectively. Increased age (P = .0241), negative Merkel cell polyomavirus status (P = .0185), and p63 positivity (P = .0012) were significantly associated with mortality. The latter 2 variables were highly correlated (P = .004). The interclass correlation between the 2 sets of H-scores was 0.95. Our findings support an association between p63 expression and reduced overall survival in MCC and show consistency in scoring this prognostic parameter. TAp63 is the dominant isoform of the protein involved. The paradoxical tumor suppressor-like activity of this isoform in p63-positive MCCs with reduced overall survival requires further study.

Danger is only skin deep: aggressive epidermal carcinomas. An overview of the diagnosis, demographics, molecular-genetics, staging, prognostic biomarkers, and therapeutic advances in Merkel cell carcinoma

Merkel cell carcinoma (MCC) is a high grade primary cutaneous neuroendocrine carcinoma and is among the most aggressive cutaneous malignancies. The rising incidence of MCC, together with its often rapidly aggressive course, underscore a critical need to recognize the histopathologic and the immunohistochemical features that inform its accurate diagnosis. In the current review, we summarize the current state of knowledge regarding the accurate diagnosis of MCC and the exclusion of other entities in the differential diagnosis. We provide a comprehensive review of genomic studies that identified the molecular-genetic drivers of MCC as well as a summary of studies identifying prognostic biomarkers that can facilitate risk stratification. Importantly, Merkel cell polyomavirus (MCPyV) appears to be causative in most cases of MCC and represents both a diagnostic and prognostic marker. Finally, as staging of MCC has undergone critical refinements with the introduction of the 8th Edition of the American Joint Committee on Cancer staging system, we provide an update on MCC staging. In particular, the prognostic significance of the sentinel lymph node (SLN) in MCC necessitates a systematic approach to its evaluation and diagnosis to ensure accurate and consistent risk stratification for patients, and we therefore provide a comprehensive overview of SLN evaluation in MCC. Finally, the intimate relationship between MCC and the integrity of the host immune system has led to paradigm-shifting therapeutic advances with the successful application of immune checkpoint blockade to treat patients with advanced disease, and we therefore summarize those studies and the correlative studies in which predictive biomarkers have been identified.

p63 Is a Promising Marker in the Diagnosis of Unusual Skin Cancer

Skin cancer is the most common type of cancer worldwide. Ozone depletion and climate changes might cause a further increase in the incidence rate in the future. Although the early detection of skin cancer enables it to be treated successfully, some tumours can evolve and become more aggressive, especially in the case of melanoma. Therefore, good diagnostic and prognostic markers are needed to ensure correct detection and treatment. Transcription factor p63, a member of the p53 family of proteins, plays an essential role in the development of stratified epithelia such as skin. In this paper, we conduct a comprehensive review of p63 expression in different types of skin cancer and discuss its possible use in the diagnosis and prognosis of cutaneous tumours.

The uterine epithelial loss of Pten is inefficient to induce endometrial cancer with intact stromal Pten

Mutation of the tumor suppressor Pten often leads to tumorigenesis in various organs including the uterus. We previously showed that Pten deletion in the mouse uterus using a Pgr-Cre driver (Ptenf/fPgrCre/+) results in rapid development of endometrial carcinoma (EMC) with full penetration. We also reported that Pten deletion in the stroma and myometrium using Amhr2-Cre failed to initiate EMC. Since the Ptenf/fPgrCre/+ uterine epithelium was primarily affected by tumorigenesis despite its loss in both the epithelium and stroma, we wanted to know if Pten deletion in epithelia alone will induce tumorigenesis. We found that mice with uterine epithelial loss of Pten under a Ltf-iCre driver (Ptenf/f/LtfCre/+) develop uterine complex atypical hyperplasia (CAH), but rarely EMC even at 6 months of age. We observed that Ptenf/fPgrCre/+ uteri exhibit a unique population of cytokeratin 5 (CK5) and transformation related protein 63 (p63)-positive epithelial cells; these cells mark stratified epithelia and squamous differentiation. In contrast, Ptenf/fLtfCre/+ hyperplastic epithelia do not undergo stratification, but extensive epithelial cell apoptosis. This increased apoptosis is associated with elevation of TGFβ levels and activation of downstream effectors, SMAD2/3 in the uterine stroma. Our results suggest that stromal PTEN via TGFβ signaling restrains epithelial cell transformation from hyperplasia to carcinoma. In conclusion, this study, using tissue-specific deletion of Pten, highlights the epithelial-mesenchymal cross-talk in the genesis of endometrial carcinoma.

Immunohistochemical profiles of different subsets of Merkel cell carcinoma

The literature records many examples of Merkel cell carcinoma (MCC) exhibiting aberrant immunohistochemical profiles. These can lead to diagnostic difficulty. The objectives of the current study were (1) to examine the immunohistochemical profile of different subsets of MCC to determine whether predictable subset-specific patterns exist and (2) to establish whether shared immunophenotypic patterns might reveal links between individual subsets, as demonstrated previously at a genetic level. In 52 cases of MCC, stratified by viral status and morphology, we studied 5 markers commonly used in the diagnostic evaluation of these tumors (CK20, CK7, chromogranin, neurofilament and TTF-1). Expression of these proteins was recorded as quantitative (H-scores) and absolute (positive vs negative) variables. In general, our data indicate that the "classical" or expected panel (CK20+, NF+, Chromo+, TTF-1, CK7-) is observed significantly more often in pure Merkel cell polyomavirus (MCPyV)-positive than in MCPyV-negative cases (78% vs 25%; P = .002). Neurofilament was less frequently encountered in MCPyV-negative than in MCPyV-positive tumors (66.7% vs 100%; P = .001) and expression of TTF-1 (37.5% vs 3.6%; P = .003) and CK7 (45.8 vs 14.3; P = .02) was more frequent. No significant immonophenotypic differences were observed between pure and combined MCPyV-negative tumors. Recognition of the more aberrant immunohistochemical profile of MCPyV-negative MCC should inform the diagnostic approach to this tumor. Moreover, the shared aberrant immunophenotype in pure and combined MCPyV-negative tumors supports a link between these entities and serves to separate them from MCPyV-positive tumors.

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.

Increased expression of EZH2 in Merkel cell carcinoma is associated with disease progression and poorer prognosis

Enhancer of zeste homolog 2 (EZH2) is a histone methyltransferase that affects tumorigenesis by epigenetic gene silencing. Merkel cell carcinoma (MCC) is a rare cutaneous neuroendocrine carcinoma that has a high risk of disease progression with nodal and distant metastases. Here, we evaluated EZH2 expression by immunohistochemistry in a cohort of 85 MCC tumors (29 primary tumors, 41 lymph node metastases, 13 in-transit metastases, and 2 distant metastases) with clinical follow-up. We show strong/moderate EZH2 expression in 54% of tumors. Importantly, weak expression of EZH2 in the primary tumor, but not nodal metastases, correlated with improved prognosis compared to moderate/strong EZH2 expression (5-year MCC-specific survival of 68% versus 22%, respectively, P=.024). In addition, EZH2 was expressed at higher levels in nodal metastases compared to primary tumors (P=.005). Our data demonstrate that EZH2 has prognostic value and may play an oncogenic role in MCC.

Application of Immunohistochemistry in the Diagnosis of Pulmonary and Pleural Neoplasms

CONTEXT

- A vast majority of neoplasms arising from lung or pleura are initially diagnosed based on the histologic evaluation of small transbronchial, endobronchial, or needle core biopsies. Although most diagnoses can be determined by morphology alone, immunohistochemistry can be a valuable diagnostic tool in the workup of problematic cases.

OBJECTIVE

- To provide a practical approach in the interpretation and immunohistochemical selection of lung/pleura-based neoplasms obtained from small biopsy samples.

DATA SOURCES

- A literature review of previously published articles and the personal experience of the authors were used in this review article.

CONCLUSION

- Immunohistochemistry is a useful diagnostic tool in the workup of small biopsies from the lung and pleura sampled by small biopsy techniques.

Update on Merkel Cell Carcinoma

Merkel cell carcinoma (MCC) is a rare, aggressive cutaneous neuroendocrine malignancy. Merkel cell polyomavirus, a tumorigenic DNA virus, is present in most MCC tumors, with implications for tumor biology, diagnosis, and management. Merkel cell polyomavirus-negative tumors have a high burden of UV-signature mutations, similar to melanoma. The histopathologic diagnosis of MCC requires immunohistochemistry to exclude morphologically similar entities. Therapies for advanced disease are currently lacking. Here, the features of MCC are reviewed, including recent molecular discoveries with implications for improved therapy for advanced disease.

Merkel Cell Carcinoma

Merkel cell carcinoma (MCC) encompasses neuroendocrine carcinomas primary to skin and occurs most commonly in association with clonally integrated Merkel cell polyomavirus with related retinoblastoma protein sequestration or in association with UV radiation-induced alterations involving the TP53 gene and mutations, heterozygous deletion, and hypermethylation of the Retinoblastoma gene. Molecular genetic signatures may provide therapeutic guidance. Morphologic features, although patterned, are associated with predictable diagnostic pitfalls, usually resolvable by immunohistochemistry. Therapeutic options for MCC, traditionally limited to surgical intervention and later chemotherapy and radiation, are growing, given promising early results of immunotherapeutic regimens.

Shared Oncogenic Pathways Implicated in Both Virus-Positive and UV-Induced Merkel Cell Carcinomas

Merkel cell carcinoma (MCC) is a highly malignant neuroendocrine tumor of the skin whose molecular pathogenesis is not completely understood, despite the role that Merkel cell polyomavirus can play in 55-90% of cases. To study potential mechanisms driving this disease in clinically characterized cases, we searched for somatic mutations using whole-exome sequencing, and extrapolated our findings to study functional biomarkers reporting on the activity of the mutated pathways. Confirming previous results, Merkel cell polyomavirus-negative tumors had higher mutational loads with UV signatures and more frequent mutations in TP53 and RB compared with their Merkel cell polyomavirus-positive counterparts. Despite important genetic differences, the two Merkel cell carcinoma etiologies both exhibited nuclear accumulation of oncogenic transcription factors such as NFAT or nuclear factor of activated T cells (NFAT), P-CREB, and P-STAT3, indicating commonly deregulated pathogenic mechanisms with the potential to serve as targets for therapy. A multivariable analysis identified phosphorylated CRE-binding protein as an independent survival factor with respect to clinical variables and Merkel cell polyomavirus status in our cohort of Merkel cell carcinoma patients.

Merkel Cell Carcinoma: An Update of Key Imaging Techniques, Prognostic Factors, Treatment, and Follow-up

Merkel cell carcinoma, though rare, is one of the most aggressive tumors a dermatologist faces. More than a third of patients with this diagnosis die from the disease. Numerous researchers have attempted to identify clinical and pathologic predictors to guide prognosis, but their studies have produced inconsistent results. Because the incidence of Merkel cell carcinoma is low and it appears in patients of advanced age, prospective studies have not been done and no clear treatment algorithm has been developed. This review aims to provide an exhaustive, up-to-date account of Merkel cell carcinoma for the dermatologist. We describe prognostic factors and the imaging techniques that are most appropriate for evaluating disease spread. We also discuss current debates on treating Merkel cell carcinoma.

Estrogen receptor β in Merkel cell carcinoma: its possible roles in pathogenesis

Sex steroids have been postulated to influence skin development and functions as well as its pathogenesis. MCC occurs in both sexes; however, the specific differences in pathogenesis among sexes have yet to be conclusively defined. The detailed status of sex steroid receptors (AR, PRA and PRB, and ERα, ERβ) are also unknown in MCC patients. We first immunolocalized sex steroid receptors and compared the results with immunolocalization of relevant transcription factors including SOX2, FOXA1, and Bcl-2 and Ki-67 in 18 cases of MCCs. AR, PRA, PRB, ERα, ERβ, Bcl-2, SOX2, and FOXA1 immunoreactivity was evaluated by using the modified H score method, and Ki-67 was quantified using labeling index. ERβ immunoreactivity was markedly present in all the cases of MCC examined, with relatively weak immunoreactivity of ERα, AR, PRA, and PRB. The status of ERβ immunoreactivity was also significantly correlated with Ki-67 labeling index and Bcl-2 score. These results demonstrated that ERβ could be associated with regulation of both cell proliferation and apoptosis in MCCs.

Density, Distribution, and Composition of Immune Infiltrates Correlate with Survival in Merkel Cell Carcinoma

PURPOSE

Merkel cell carcinoma (MCC) is an aggressive cancer with frequent metastasis and death with few effective therapies. Because programmed death ligand-1 (PD-L1) is frequently expressed in MCC, immune checkpoint blockade has been leveraged as treatment for metastatic disease. There is therefore a critical need to understand the relationships between MCPyV status, immune profiles, and patient outcomes.

EXPERIMENTAL DESIGN

IHC for CD3, CD8, PD-1, PD-L1, and MCPyV T-antigen (to determine MCPyV status) was performed on 62 primary MCCs with annotated clinical outcomes. Automated image analysis quantified immune cell density (positive cells/mm²) at discrete geographic locations (tumor periphery, center, and hotspot). T-cell receptor sequencing (TCRseq) was performed in a subset of MCCs.

RESULTS

No histopathologic variable associated with overall survival (OS) or disease-specific survival (DSS), whereas higher CD3⁺ (P = 0.004) and CD8⁺ (P = 0.037) T-cell density at the tumor periphery associated with improved OS. Higher CD8⁺ T-cell density at the tumor periphery associated with improved DSS (P = 0.049). Stratifying MCCs according to MCPyV status, higher CD3⁺ (P = 0.026) and CD8⁺ (P = 0.015) T-cell density at the tumor periphery associated with improved OS for MCPyV⁺ but not MCPyV^- MCC. TCRseq revealed clonal overlap among MCPyV⁺ samples, suggesting an antigen-specific response against a unifying antigen.

CONCLUSIONS

These findings establish the tumor-associated immune infiltrate at the tumor periphery as a robust prognostic indicator in MCC and provide a mechanistic rationale to further examine whether the immune infiltrate at the tumor periphery is relevant as a biomarker for response in ongoing and future checkpoint inhibitor trials in MCC. Clin Cancer Res; 22(22); 5553-63. ©2016 AACR.

Merkel Cell Carcinoma: Current Issues Regarding Diagnosis, Management, and Emerging Treatment Strategies

Merkel cell carcinoma (MCC) is a rare but aggressive cutaneous tumor with a predilection for the head and neck of elderly Caucasian patients. Although much less common than melanoma, MCC has higher rates of sentinel lymph node involvement, local and regional recurrences, and mortality. The majority of MCC cases have been linked to the relatively newly discovered Merkel cell polyomavirus, which is a ubiquitous constituent of the skin flora. Recent discoveries regarding viral integration and carcinogenesis and the immunologic features of MCC have expanded the understanding of MCC. These discoveries have led to the development and application of emerging therapies such as somatostatin analogs, immune checkpoint inhibition, adoptive cell therapy, and other exciting possibilities for targeted therapy.

Cutaneous squamous and neuroendocrine carcinoma: genetically and immunohistochemically different from Merkel cell carcinoma

Cutaneous neuroendocrine (Merkel cell) carcinoma most often arises de novo in the background of a clonally integrated virus, the Merkel cell polyomavirus, and is notable for positive expression of retinoblastoma 1 (RB1) protein and low expression of p53 compared with the rare Merkel cell polyomavirus-negative Merkel cell carcinomas. Combined squamous and Merkel cell tumors are consistently negative for Merkel cell polyomavirus. Little is known about their immunophenotypic or molecular profile. Herein, we studied 10 combined cutaneous squamous cell and neuroendocrine carcinomas for immunohistochemical expression of p53, retinoblastoma 1 protein, neurofilament, p63, and cytokeratin 20 (CK20). We compared mutation profiles of five combined Merkel cell carcinomas and seven 'pure' Merkel cell carcinomas using targeted next-generation sequencing. Combined tumors were from the head, trunk, and leg of Caucasian males and one female aged 52-89. All cases were highly p53- and p63-positive and neurofilament-negative in the squamous component, whereas RB1-negative in both components. Eight out of 10 were p53-positive, 3/10 p63-positive, and 3/10 focally neurofilament-positive in the neuroendocrine component. Six out of 10 were CK20-positive in any part. By next-generation sequencing, combined tumors were highly mutated, with an average of 48 mutations per megabase compared with pure tumors, which showed 1.25 mutations per megabase. RB1 and p53 mutations were identified in all five combined tumors. Combined tumors represent an immunophenotypically and genetically distinct variant of primary cutaneous neuroendocrine carcinomas, notable for a highly mutated genetic profile, significant p53 expression and/or mutation, absent RB1 expression in the context of increased RB1 mutation, and minimal neurofilament expression.

Merkel Cell Carcinoma Analysis of Outcomes: A 30-Year Experience

BACKGROUND

Merkel cell carcinoma (MCC) is an aggressive cutaneous malignancy with poor prognosis. Limited data exists to guide treatment decisions. Here we report on our institutional experience and outcomes treating patients with MCC.

METHODS

A database search (1984-2014) of patients treated at the University of Wisconsin Hospital and Clinics was used to identify patients with histologically confirmed MCC. Patient, tumor, and treatment characteristics were examined via review of medical records. Statistical analyses were performed to assess outcomes and associated prognostic factors.

RESULTS

A total of 87 patients with MCC were identified with a median follow-up of 17 months (mean: 38, range: 0-210 months). Two and five-year overall survival rates were 53.9% and 32.8%, respectively. Recurrence was documented in 31.0% of patients (85.2% locoregional, 48.1% distant and 33.3% both). Patients with a history of immunosuppression exhibited significantly worse survival (hazard ratio, 2.01; 95% CI, 1.1-3.7) when compared to immune-competent individuals. The head and neck region was the most common location of primary lesion (N=49) followed by the extremities (N=31). Upper extremity primaries predicted significantly better overall survival (hazard ratio, 0.48; 95% CI, 0.23-0.99) while lower extremity primaries did not have significantly better results (hazard ratio, 0.5; 95% CI, 0.21-1.2) in comparison to head and neck site of primary. Nodal involvement (hazard ratio, 2.95; 95% CI, 1.5-5.79) was also a negative prognostic factor associated with poor overall survival when compared with clinically node negative patients. Primary tumor size > 2 cm (hazard ratio, 1.76; 95% CI, 0.91-3.4) was not associated with survival.

CONCLUSIONS

This study highlights the role of various factors in determining prognosis of Merkel cell carcinoma; history of immunosuppression, nodal involvement, and head/neck primary predicted worse overall survival. These findings suggest that improvements in both distant and locoregionally directed therapies might play an important role in control of MCC and identify areas for future study.

[Merkel cell carcinoma]

Merkel cell carcinoma is a rare aggressive malignant neuroendocrine skin tumor, which can metastasize to lymph nodes early and often shows local recurrence. The prognosis depends on tumor size and disease stage. The majority of recurrences appear during the first 2 years after the primary diagnosis. The 5-year survival rate for primary tumor < 2 cm is 66-75 % and for primary tumors > 2 cm is 50-60 %. With lymph node metastases the 5-year survival rate is 42-52 %, while with distant metastases it drops to 17-12 %. Extensive staging inclusive sentinel lymph node biopsy is essential to assess the risk for distant metastasis and to allow the best recommendations for therapy. After surgical treatment with adequate safety margin, subsequent adjuvant radiation therapy of the tumor region and lymphatic draining basin is recommended to reduce the risk of local recurrence and lymphatic spread.

Pure versus combined Merkel cell carcinomas: immunohistochemical evaluation of cellular proteins (p53, Bcl-2, and c-kit) reveals significant overexpression of p53 in combined tumors

Merkel cell polyomavirus is of oncogenic significance in approximately 80% of Merkel cell carcinomas. Morphological subcategories of the tumor differ in regard to viral status, the rare combined type being uniformly virus negative and the predominant pure type being mainly virus positive. Indications that different biological subsets of the tumor exist led us to explore this diversity. In an Eastern Canadian cohort of cases (75 patients; mean age, 76 years [range, 43-91]; male/female ratio, 43:32; 51 [68%] pure and 24 [34%] combined tumors), we semiquantitatively compared the immunohistochemical expression of 3 cellular proteins (p53, Bcl-2, and c-kit) in pure versus combined groups. Viral status was known in a subset of cases. The significant overexpression of p53 in the combined group (mean [SD], 153.8 [117.8] versus 121.6 [77.9]; P = .01) and the increased epidermal expression of this protein (p53 patches) in the same group lend credence to a primary etiologic role for sun damage in these cases. Expression of Bcl-2 and c-kit did not differ significantly between the 2 morphological groups. A relative increase in c-kit expression was significantly associated with a virus-negative status (median [interquartile range], 100 [60-115] versus 70 [0-100]; P = .03). Emerging data reveal divergent biological pathways in Merkel cell carcinoma, each with a characteristic immunohistochemical profile. Virus-positive tumors (all pure) exhibit high retinoblastoma protein and low p53 expression, whereas virus-negative cases (few pure and all combined) show high p53 and relatively high c-kit expression. The potential biological implications of this dichotomy call for consistent stratification of these tumors in future studies.

Clinical and Pathologic Study of Feline Merkel Cell Carcinoma With Immunohistochemical Characterization of Normal and Neoplastic Merkel Cells

The authors herein describe the morphologic and immunohistochemical features of normal Merkel cells as well as the clinicopathologic findings of Merkel cell carcinoma in cats. Merkel cells were characterized as vacuolated clear cells and were individually located in the epidermal basal layer of all regions examined. Clusters of Merkel cells were often observed adjacent to the sinus hair of the face and carpus. Immunohistochemically, Merkel cells were positive for cytokeratin (CK) 20, CK18, p63, neuron-specific enolase, synaptophysin, and protein gene product 9.5. Merkel cell carcinoma was detected as a solitary cutaneous mass in 3 aged cats (13 to 16 years old). On cytology, large lymphocyte-like cells were observed in all cases. Histologic examinations of surgically resected tumors revealed nests of round cells separated by various amounts of a fibrous stroma. Tumor cells were commonly immunopositive for CK20, CK18, p63, neuron-specific enolase, and synaptophysin, representing the characteristics of normal Merkel cells.

Detection of mitotic figures and G2+ tumor nuclei with histone markers correlates with worse overall survival in patients with Merkel cell carcinoma

BACKGROUND

High mitotic figure count (MFC) correlates with low survival rate in Merkel cell carcinoma (MCC). However, the prognostic impact of histone biomarkers as surrogates of MFC in MCC is unknown. We evaluated the prognostic significance of the immunodetection of mitotic figures and of G2+ tumor nuclei with histone-associated mitotic markers H3K79me3T80ph (H3KT) and phosphohistone H3 (PHH3) in MCC.

METHODS

Immunohistochemical analyses of H3KT and PHH3 and proliferative marker Ki-67 were performed in a series of 21 cases of MCC. The significance of the pathologic data and immunoreactivity with these markers was evaluated with Pearson correlation and paired Student t-test. Univariate Cox proportional hazards regression models were performed to assess the relationships between these markers and survival.

RESULTS

H3KT detected a higher number of mitotic figure (p<0.0001) and G2+ tumor nuclei (p<0.0052) than did PHH3. Furthermore, the MFC combined with G2+ tumor nuclei detected with H3KT compared to PHH3 and manual MFC was a significant predictor of impaired survival in patients with MCC (p=0.035; HR=1.0172), corresponding to a 1.72% increased risk of death for each unit increase in H3KT.

CONCLUSIONS

Biomarker analysis of proliferative rates with histone markers may have relevance in stratifying risk in patients with MCC.

Merkel cell polyomavirus small T antigen is oncogenic in transgenic mice

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

Working formulation of neuroendocrine tumors of the skin and breast

In the skin and breast, endocrine tumors are composed of a heterogeneous mixture of endocrine and exocrine cells. The definition of "pure" endocrine carcinomas is a matter for debate, and as a consequence, there is lack of uniform diagnostic criteria. There are no significant clinical differences in either overall or disease-free survival between matched neoplasms with endocrine and without endocrine differentiation nor between the degree of endocrine differentiation and tumor size, stage, or prevalence of vascular invasion for both sites (skin and breast). Here, endocrine tumors of the skin and breast are grouped respectively into three categories that include most of the neuroendocrine tumors of the skin and breast as seen in routine practice. It was felt that the number of different types of neuroendocrine tumors is so conspicuous that it is impossible to organize them in an orderly classification. It has been proposed therefore, for practical diagnostic routine purposes, to arrange these neoplasms into a working formulation. The latter includes heterogeneous lesions respectively of the skin and breast within the same group that have clinical features in common.

Merkel cell carcinoma - recent advances in the biology, diagnostics and treatment

Merkel cell carcinoma (MCC) is an uncommon primary cutaneous carcinoma with neuroendocrine differentiation. Since recent discovery of MCCs strong association with Merkel cell polyomavirus (MCPyV), there has been a rapid increase in the understanding of the carcinomas genetics, molecular biology and pathogenesis. In our study, we reviewed recent advances and controversies concerning MCC histogenesis, epidemiology, diagnostic and prognostic markers. We analyzed the association of MCPyV with MCC and the possible new targets for therapy. We also examined English-based literature regarding MCC pathogenesis published between 2008 and 2013, which lead to a deeper understanding of the topic. Our study showed that the association of MCPyV strongly influences the course of MCC. Additionally, it has been shown that a immunological response to MCPyV may in the future give hope to identify new therapeutic strategies in treatment of this fatal malignancy. This article is part of a Directed Issue entitled: Rare Cancers.

Melanotic and non-melanotic malignancies of the face and external ear - A review of current treatment concepts and future options

Skin has the highest incidence and variety of tumors of all organs. Its structure is of great complexity, and every component has the potential to originate a skin neoplasm (SN). Because of its exposed nature, skin is vulnerable to carcinogenic stimuli such as UV radiation. Various entities can cause SN. Nonmelanotic skin cancers (NMSC) are the most common of all cancers, with over one million cases diagnosed annually in the US. Basal cell carcinoma (BCC) accounts for approximately 80% of all NMSC, most of the remaining 20% being squamous cell carcinoma (SCC). The skin of the head and neck is the most common site for tumors, accounting for more than 80% of all NMSC. BCC, SCC, and malignant melanomas (MM) represent 85-90% of all SN. Merkel cell tumors (MCC), lymphoepithelioma-like carcinomas of the skin (LELCS), dermato-fibro-sarcomas, leiomyosarkomas, and Kaposi-sarcomas are less frequent in the facial skin region and the external ear. Based on data from the German Federal Cancer Registry (2003/2004), 140,000 people in Germany were affected by SN (100,000 BCC, 22,000 SCC, 22,000 MM). This number increases considerably if malignant precursors, such as actinic keratosis, are included. Each year, the frequency of SN diagnosis rises by 3-7%. Among all known malignant tumors, MM exhibits the highest rate of increase in incidence. In the past, SN was primarily diagnosed in people aged 50 years or older. However, recently, the risk for developing SN has shifted, and younger people are also affected. Early diagnosis is significantly correlated with prognosis. Resection of SN creates defects that must be closed with local or microvascular flaps to avoid functional disturbing scar formation and deflection of the nose, eyelids, or lips. All therapeutic strategies for SN, the current standard for adjuvant and systemic treatment, and the management of the increasing number of patients under permanent blood thinner medication are described with regard to the treatment of SN.

p63 and Ki-67 immunostainings in laryngeal squamous cell carcinoma are related to survival

To examine the prognostic significance of the immunohistochemical expression of p63 and Ki-67 oncoproteins in patients with laryngeal squamous cell carcinoma, a retrospective evaluation was carried out on a cohort of 108 patients with primary laryngeal squamous cell carcinoma (LSCC) treated by primary surgery. For the immunohistochemical evaluation, tissue section obtained by formalin-fixed and paraffin-embedded tissue blocks from resection of each patient was used. Clinicopathologic data were associated with the immunostaining results. The association among the considered variables was assessed by Fisher's exact test, Mann-Whitney test, non-parametric χ(2) test, and Spearman's rho rank test was used to assess the relations among them. Differences in p63 and Ki-67 immunoreactivity among the different groups were compared via Kruskal-Wallis test and post hoc tests were performed using Mann-Whitney test with Bonferroni correction. The overall survival rate was estimated via Kaplan-Meier method, and the cumulative incidence functions for different groups were compared using log-rank statistics. Cox proportional hazard model was employed in a multivariate analysis to assess the effect of prognostic factors in the overall survival rate. Furthermore, taking into account death due to other causes, we estimated LSCC-related survival and disease-free survival rates using competing risk analysis. The results of immunohistochemical examination showed a statistically significant relationship between the up-regulation of P63 and Ki-67, an increase in histological grading, and primary tumours associated with lymph node metastases. p63 and Ki-67 up-regulation was related to a shorter disease-free survival and a significant association was found between p63 and Ki-67 percentage of positive cells and patient survival. Finally, we noticed a significant relation between p63 and Ki-67 (ρ = 0.87). On the other hand, no statistically significant associations were found between p63 and Ki-67 down-regulation and clinicopathologic data. Our findings suggest that abnormal p63 and Ki-67 immunoreactivity may be involved in the early phases of laryngeal tumorigenesis and may become a significant prognostic predictor for both overall and disease-free survivals. These biomarkers could thus help in the selection of high-risk patients with LSCC who may benefit from more aggressive therapy or chemoprevention.

Support for p63 expression as an adverse prognostic marker in Merkel cell carcinoma: report on a Canadian cohort

Recent evidence has invoked immunohistochemical expression of p63 in Merkel cell carcinoma as an adverse prognostic factor. Conflicting data led us to evaluate this. An Eastern Canadian cohort diagnosed between 1990 and 2012 was studied. Demographic and clinical data were obtained from pathology records and Provincial Cancer Registries. Pathological features were evaluated by the investigators. Merkel cell polyomavirus status was known in a subset of cases. Clinicopathological features were correlated with overall survival. The cohort consisted of 83 patients (mean age, 75.8 ± 11.7 years) with a male/female ratio of 1.24:1. In a mean follow-up period of 175 weeks (±177), 51 patients died (61.4%). Of several parameters examined, 6 showed significant adverse associations with survival on univariate analysis: age (hazard ratio [HR], 1.05 [1.02-1.08]), clinical stage (III/IV versus I/II; HR, 2.24 [1.18-4.27]), tumor size (HR, 1.16 [1.05-1.28]), combined versus pure morphology (HR, 1.82 [1.04-3.18]), minimal tumor-infiltrating lymphocytes (HR, 2.23 [1.04-4.78]), and expression of p63 (positive in 49.4%; HR, 1.93 [1.09-3.43]). In the stage I/II subgroup, p63 expression was associated with a trend toward poor survival. On multivariate analysis, p63 expression was not significantly associated with reduced survival. Our data support existing evidence that p63 expression in Merkel cell carcinoma carries adverse implications for survival. That it was not an independent prognostic factor may be due to study size and/or its potential as a confounding variable with clinical stage. Of clinical importance is its association with a trend toward a poor outcome in early stage disease.

Merkel cell carcinoma: case study and literature review

Merkel cell carcinoma is a rare, aggressive, highly metastatic, often fatal, primary neuroendocrine tumor typically located on sun-exposed skin. It is frequently found in white males aged 60 to 70 years. The somewhat typical benign clinical appearance of the lesion can result in a delayed diagnosis, leading to a less than optimal outcome.