Primary neuroendocrine (Merkel cell) carcinoma of the skin: morphologic diversity and implications thereof

When biopsy alone is not enough for the diagnosis: angiomatous florid proliferation hiding a merkel cell carcinoma

Merkel cell carcinoma (MCC) is an aggressive tumor with an uncertain histogenesis typically arising on sun-damaged skin of the elderly. It has rarely been described in association with other tumors such as epithelial, melanocytic, and mesenchymal, but not vascular neoplasias. However, an exuberant vascular reaction is considered a common phenomenon in neuroendocrine neoplasms, where it can even obscure the proliferating cells and mimic a primary vascular neoplasia. A 47-year-old man was referred for the evaluation of a long-lasting reddish skin tumor located on the right buttock. After 2 punch biopsies, the patient underwent surgical excision of the lesion. Histological examination showed a dermal florid, benign vascular proliferation overlying some large deep coalescent nodules made up of monomorphous round cells with scant cytoplasm and a high mitotic activity. After the appropriate immunohistochemical stainings, a final diagnosis of hemangioma overlying a previously unrecognized MCC was rendered. Whether the angiomatous proliferation should be considered an exuberant reaction to the tumor, induced by an angiogenetic drive, or a true hemangioma is somewhat controversial. The main point is that such a neoplastiform angiomatous proliferation may represent a potential diagnostic pitfall, especially in limited specimens, and that an accurate clinicopathologic correlation is always needed. In our case, even if additional punch biopsies had been performed, the vascular proliferation would dominate the histological picture and an accurate diagnostic conclusion would probably not be reached due to the deep location of the MCC.

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.

Fine-needle aspiration cytology of Merkel cell carcinoma-a review of 69 cases

This study reviewed the clinical presentation, cytologic findings, and the immunophenotype of 69 Merkel cell carcinoma (MCC) cases sampled by fine-needle aspiration (FNA).  Demographic and clinical data, the cytology findings, and results of ancillary testing were reviewed.  Median patient age was 78 years (37-104) with a 1:1.8 female to male ratio. The most common FNA sites sampled included lymph nodes in the neck, the axillary region, the inguinal region and the parotid gland. Most patients had a history of MCC (68%) and/or non-MCC malignancy (70%).  The common cytologic pattern was a cellular smear with malignant cells arranged in a dispersed pattern with variable numbers of disorganized groups of cells. Cytoplasm was scant or absent and nuclei showed mild to moderate anisokaryosis, stippled chromatin, inconspicuous nucleoli, and nuclear molding. Numerous apoptotic bodies were often present.  Cell block samples (28 cases) were usually positive for cytokeratins in a perinuclear dot pattern, including 88% of cases with CK20 positivity. CD56 was the most sensitive (95%) neuroendocrine marker on cell blocks and was also positive with flow cytometry in nine cases tested.  MCC is most commonly seen in FNA specimens from the head and neck of elderly patients, often with a history of previous skin lesions. Occasional cases present in younger patients and some may be mistaken for other round blue cell tumors, such as lymphoma. CD 56 may be a useful marker in cell block preparations and in flow cytometric analysis of MCC.

Primary gastric Merkel cell carcinoma harboring DNA polyomavirus: first description of an unusual high-grade neuroendocrine carcinoma

Merkel cell carcinoma (MCC) is a skin cancer that can also rarely arise in extracutaneous sites including mucosal surfaces. About 80% of MCCs harbor the Merkel cell polyomavirus (MCPyV). All cases of gastric MCCs so far reported were metastases from cutaneous sources. In the present article, we describe for the first time a primary gastric MCC harboring MCPyV. A 72-year-old man presented to clinical observation due to epigastric pain. Upper endoscopy revealed an ulcerated gastric tumor. The patient underwent total gastrectomy. The tumor was composed of mitotically active monomorphic small cells showing round nuclei with finely dispersed chromatin arranged in sheets and nests with large areas of necrosis. Tumor cells were positive for neuroendocrine markers and showed paranuclear dot immunoreactivity for cytokeratin 20. MCPyV was demonstrated with immunohistochemistry and electron microscopy, which showed intranuclear and intracytoplasmic viral particles. The MCPyV DNA in tumor cells was demonstrated with polymerase chain reaction analysis.

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 with divergent differentiation: histopathological and immunohistochemical study of 15 cases with PCR analysis for Merkel cell polyomavirus

AIMS

To report on 15 cases of Merkel cell carcinoma (MCC) with divergent differentiation, to characterize its clinicopathological spectrum and its relationship with Merkel cell polyomavirus (MCV).

METHODS AND RESULTS

Fifteen patients with a mean age of 81 years were included. Follow-up was available for 13 cases (range 12 days to 6 years; median 6 months). Recurrence, metastasis and mortality rates were 15.4%, 53.8% and 61.5%, respectively. All tumours showed the typical histological and immunohistochemical features of MCC, with at least one additional divergent component. Eight cases had a single aberrant component (squamous in six cases, follicular in one case, and porocarcinoma in one case), six cases had two aberrant components (squamous and sarcomatous in three cases, glandular and squamous in two cases, and sarcomatous and neuroblastic in one case), and one case had three aberrant components (glandular, squamous, and sarcomatous). All cases had dysplastic changes in the overlying epithelium, and four of 15 showed epidermotropism. PCR analysis for Merkel cell polyomavirus (MCV) gave negative results in all 12 cases tested.

CONCLUSIONS

Merkel cell carcinoma with divergent differentiation is a highly aggressive tumour that might be difficult to recognize, owing to its wide histological variability. Negativity for MCV suggests that the virus is not implicated in the development of this subtype of MCC.

Clinicopathologic features of primary Merkel cell carcinoma: a detailed descriptive analysis of a large contemporary cohort

BACKGROUND

Little uniformity exists in the clinical and histologic variables reported with primary Merkel cell carcinoma (MCC).

OBJECTIVE

To provide a rigorous descriptive analysis of a contemporary cohort and promote the prospective collection of detailed data on MCC for future outcome studies.

METHODS AND MATERIALS

A detailed descriptive analysis was performed for clinical and histologic features of 147 patients with 150 primary MCC tumors in a prospectively collected database from 2006 to 2010.

RESULTS

The majority (73.5%) of patients were at American Joint Committee on Cancer clinical stage I or II at presentation, 20.4% at stage III, and 6.1% at stage IV. Detailed descriptive clinical and histologic findings are presented.

CONCLUSION

Clinical and histologic profiling of primary MCC in the literature is variable and limited. Systematic prospective collection of MCC data is needed for future outcome studies and the ability to compare and share data from multiple sources for this relatively rare tumor.

[A probable etiological role of Merkel cell polyomavirus in the development of Merkel cell carcinoma]

Approximately 20% of the tumours in humans are associated with contagious viral agents. Merkel cell carcinoma is a rare and highly aggressive tumour which may originate from the epidermal stratum basale, although the origin is still controversial. This tumour is most commonly found in elderly and immunocompromised patients in sun exposed areas, especially in the head and neck regions. Merkel cell carcinoma often causes a diagnostic challenge with a dramatically increasing incidence. In 2008, a DNA tumour virus, a polyomavirus (Merkel cell polyomavirus) was detected in Merkel cell carcinomas, and this finding helped to understand the etiological background of the disease. The infectious - probably viral - etiology resulted in a paradigm shift in pathogenesis and, hopefully, in therapy as well. This review summarizes the current knowledge related to Merkel cell carcinoma and the first oncogenic human polyomavirus, the Merkel cell polyomavirus, to promote the clinical adaptation of the information.

Which are the cells of origin in merkel cell carcinoma?

Merkel cell carcinoma (MCC), a highly aggressive skin tumour with increasing incidence, is associated with the newly discovered Merkel cell polyomavirus (MCPyV). Studies on MCC and MCPyV as well as other risk factors have significantly increased our knowledge of MCC pathogenesis, but the cells of origin, which could be important targets in future therapies, are still unknown. Merkel cells (MCs), the neuroendocrine cells of the skin, were believed to be at the origin of MCC due to their phenotypic similarities. However, for several reasons, for example, heterogeneous differentiation of MCCs and postmitotic character of MCs, it is not very likely that MCC develops from differentiated MCs. Skin stem cells, probably from the epidermal lineage, are more likely to be cells of origin in MCC. Future studies will have to address these questions more directly in order to identify the physiological cells which are transformed to MCC cells.

The Merkel cell carcinoma challenge: a review from the fine needle aspiration service

Merkel cell carcinoma (MCC) is a highly aggressive neuroendocrine carcinoma of the skin that occurs primarily in elderly or immunocompromised patients. For this report, the authors reviewed the diagnostic challenges associated with MCC encountered on their fine-needle aspiration (FNA) service and also conducted an in-depth review of the literature on MCC. A computer search for patients who were diagnosed with MCC by FNA at the authors' institution from 2006 to 2010 was conducted, and 5 patients were selected for cytologic and immunochemical analyses based on their varied and diagnostically challenging clinical presentations. The 5 selected patients had clinical findings commonly associated with MCC, including advanced age (4 of the 5 patients were ages 75-85 years) and a history of previous malignancies (3 of the 5 patients had a history of previous malignancy), and 1 patient was diagnosed with a concomitant low-grade lymphoma. The patients and their disease illustrated the protean clinical presentation of MCC and the clinical and cytologic challenges associated with this neoplasm. The current findings indicate the need for cytopathologists to be aware of the deceptive presentation of this neoplasm and its cytologic and immunochemical features to correctly diagnose this insidious neoplasm.

Detection of Merkel cell polyomavirus in cervical squamous cell carcinomas and adenocarcinomas from Japanese patients

Background

Merkel cell polyomavirus (MCPyV) was identified originally in Merkel cell carcinoma (MCC), a rare form of human skin neuroendocrine carcinoma. Evidence of MCPyV existence in other forms of malignancy such as cutaneous squamous cell carcinomas (SCCs) is growing. Cervical cancers became the focus of our interest in searching for potentially MCPyV-related tumors because: (i) the major histological type of cervical cancer is the SCC; (ii) the uterine cervix is a common site of neuroendocrine carcinomas histologically similar to MCCs; and (iii) MCPyV might be transmitted during sexual interaction as demonstrated for human papillomavirus (HPV). In this study, we aimed to clarify the possible presence of MCPyV in cervical SCCs from Japanese patients. Cervical adenocarcinomas (ACs) were also studied.

Results

Formalin-fixed paraffin-embedded tissue samples from 48 cervical SCCs and 16 cervical ACs were examined for the presence of the MCPyV genome by polymerase chain reaction (PCR) and sequencing analyses. PCR analysis revealed that 9/48 cervical SCCs (19%) and 4/16 cervical ACs (25%) were positive for MCPyV DNA. MCPyV-specific PCR products were sequenced to compare them with reference sequences. The nucleotide sequences in the MCPyV large T (LT)-sequenced region were the same among MCPyV-positive cervical SCCs and AC. Conversely, in the MCPyV viral protein 1 (VP1)-sequenced region, two cervical SCCs and three cervical ACs showed several nucleotide substitutions, of which three caused amino acid substitutions. These sequencing results suggested that three MCPyV variants of the VP1 were identified in our cases. Immunohistochemistry showed that the LT antigen was expressed in tumor cells in MCPyV-positive samples. Genotyping of human HPV in the MCPyV-positive samples revealed that infected HPVs were HPV types 16, 31 and 58 for SCCs and HPV types 16 and 18 for ACs.

Conclusions

This study provides the first observation that MCPyV coexists in a subset of HPV-associated cervical cancers from Japanese patients. The prevalence of MCPyV in these lesions was close to that observed in the cutaneous SCCs. Further worldwide epidemiological surveys are warranted to determine the possible association of MCPyV with pathogenesis of cervical cancers.

Activation of PI3K signaling in Merkel cell carcinoma

PURPOSE

Merkel cell carcinoma (MCC) is an aggressive cutaneous neuroendocrine tumor, often metastatic at presentation, for which current chemotherapeutic regimens are largely ineffective. As its pathogenesis is still unknown, we hypothesized that deregulation of signaling pathways commonly activated in cancer may contribute to MCC tumorigenesis and may provide insights into targeted therapy approaches for this malignancy.

EXPERIMENTAL DESIGN

We retrospectively profiled 60 primary MCC samples using a SNaPshot-based tumor genotyping assay to screen for common mutations in 13 cancer genes.

RESULTS

We identified mutations in 9 (15%) MCC primary tumors, including mutations in TP53 (3 of 60) and activating mutations in the PIK3CA gene (6 of 60). Sanger sequencing of the primary MCC tumors detected one additional PIK3CA mutation (R19K) that had not been previously described in cancer. Merkel cell polyoma virus (MCPyV) was detected in 38 (66%) MCC cases and patients with MCPyV-positive cancers showed a trend toward better survival. With one exception, the presence of MCPyV and activating mutations in PIK3CA appeared mutually exclusive. We observed that signaling through the PI3K/pAKT pathway was active in one MCPyV-positive and in all MCPyV-negative MCC cell lines, as evidenced by AKT phosphorylation. Importantly, the presence of a PIK3CA-activating mutation was associated with sensitivity to treatment with ZST474, a specific phosphoinositide 3-kinase (PI3K) inhibitor, and to NVP-BEZ235, a dual PI3K/mTOR inhibitor, targeted agents under active clinical development.

CONCLUSIONS

PI3K pathway activation may drive tumorigenesis in a subset of MCC and screening these tumors for PIK3CA mutations could help identify patients who may respond to treatment with PI3K pathway inhibitors.

Merkel cell carcinoma: update and review

Merkel cell carcinoma (MCC) is a rare, aggressive, and often fatal cutaneous malignancy that is not usually suspected at the time of biopsy. Because of its increasing incidence and the discovery of a possible viral association, interest in MCC has escalated. Recent effort has broadened our breadth of knowledge regarding MCC and developed instruments to improve data collection and future study. This article provides an update on current thinking about the Merkel cell and MCC.

The spectrum of Merkel cell polyomavirus expression in Merkel cell carcinoma, in a variety of cutaneous neoplasms, and in neuroendocrine carcinomas from different anatomical sites

Most Merkel cell carcinomas display pure neuroendocrine differentiation (pure Merkel cell carcinoma), whereas a minority show combined neuroendocrine and nonneuroendocrine elements (combined Merkel cell carcinoma). Recent identification of Merkel cell polyomavirus DNA and Merkel cell polyomavirus large T antigen expression in a proportion of Merkel cell carcinomas has suggested viral-induced oncogenesis. To date, Merkel cell polyomavirus immunohistochemistry has shown an absence of viral large T antigen expression in combined Merkel cell carcinoma as well as select non-Merkel cell carcinoma cutaneous lesions and visceral neuroendocrine tumors. In our series, we aimed to further characterize the frequency and pattern of Merkel cell polyomavirus large T antigen expression by CM2B4 immunohistochemistry in primary and metastatic Merkel cell carcinoma (pure Merkel cell carcinoma and combined Merkel cell carcinoma) and various non-Merkel cell carcinoma lesions from patients with Merkel cell carcinoma, patients without Merkel cell carcinoma, and individuals with altered immune function. Merkel cell polyomavirus large T antigen was detected in 17 (63%) of 27 pure Merkel cell carcinomas and absent in all 15 (0%) combined Merkel cell carcinomas. Furthermore, complete concordance (100%) of Merkel cell polyomavirus large T antigen expression was observed in 10 cases of primary Merkel cell carcinoma and subsequent tumor metastases. We also evaluated 70 non-Merkel cell carcinoma lesions including 15 cases each of pulmonary and gastrointestinal neuroendocrine tumors. All 70 non-Merkel cell carcinoma lesions were negative for Merkel cell polyomavirus by CM2B4 immunohistochemistry, irrespective of any known Merkel cell carcinoma diagnosis and immune status. In summary, our identification of Merkel cell polyomavirus large T antigen expression in a subset of Merkel cell carcinoma and lack of findings in combined Merkel cell carcinomas and non-Merkel cell carcinoma lesions concur with earlier findings and implicate Merkel cell polyomavirus-independent pathogenesis in these cases. Overall, CM2B4 immunohistochemistry appears to be a specific method for Merkel cell polyomavirus detection and has the potential to play an important role in the diagnosis and classification of Merkel cell carcinoma in the future.

Immunohistochemistry for Merkel cell polyomavirus is highly specific but not sensitive for the diagnosis of Merkel cell carcinoma in the Australian population

Recent studies have demonstrated a high frequency of detection of Merkel cell polyomavirus in Merkel cell carcinoma. However, most of these studies are from European or North American centers that have relatively low sun exposure and may have a higher incidence of virus-driven oncogenesis compared with the highly sun-exposed but predominantly fair-skinned Australian population. We performed immunohistochemistry for Merkel cell polyomavirus on 104 cases of Merkel cell carcinoma and 74 cases of noncutaneous small cell-undifferentiated carcinoma from 3 major Australian centers. Nineteen (18.3%) cases of Merkel cell carcinoma showed positive staining for Merkel cell polyomavirus versus 1 (1.3%) of small cell-undifferentiated carcinoma. All 15 cases (14.3%) of Merkel cell carcinoma with areas of mixed squamous differentiation showed negative staining. We found positive staining in only 3 (7.7%) of 39 Merkel cell carcinoma from the head and neck (the most sun-exposed area) versus 16 (24.6%) of 65 of tumors from other sites (P < .05). Our findings support the concept of a Merkel cell polyomavirus-driven and a non-Merkel cell polyomavirus-driven (primarily sun-dependent) pathway in Merkel cell carcinoma carcinogenesis, with the latter being significantly more frequent in Australia and in mixed squamous-Merkel cell carcinoma (which is also more frequent in Australia). Although immunohistochemistry for Merkel cell polyomavirus seems to be highly specific in all populations, the low incidence of Merkel cell polyomavirus-positive Merkel cell carcinoma in a highly sun-exposed population limits its diagnostic utility in this setting.

Association of Merkel cell polyomavirus infection with morphologic differences in Merkel cell carcinoma

Recently, it has been shown that approximately 80% of Merkel cell carcinomas harbor a novel polyomavirus named Merkel cell polyomavirus, thought to be a carcinogenic agent. However, it is not fully elucidated whether Merkel cell carcinomas differ with regard to the presence or absence of Merkel cell polyomavirus. To address this, we investigated morphologic differences between Merkel cell polyomavirus-positive and -negative Merkel cell carcinomas by morphometry. Using polymerase chain reaction and real-time quantitative polymerase chain reaction, Merkel cell polyomavirus was detected in 20 (77%) of 26 Merkel cell carcinoma cases, including 4 Merkel cell carcinomas combined with squamous cell carcinomas. Interestingly, Merkel cell polyomavirus was detected only in ordinary (pure) Merkel cell carcinomas; none of the 4 combined Merkel cell carcinomas + squamous cell carcinomas was positive for Merkel cell polyomavirus (P = .001). Morphometric analyses revealed that Merkel cell polyomavirus-negative Merkel cell carcinomas had more irregular nuclei (P < .001) and more abundant cytoplasm (P = .001) than Merkel cell polyomavirus-positive Merkel cell carcinomas, which had uniform round nuclei and scant cytoplasm. Reliability of the morphometry was confirmed using intraobserver and interobserver reliability tests. These results demonstrated statistically significant differences in tumor cell morphology between Merkel cell polyomavirus-positive and -negative Merkel cell carcinomas and reconfirmed the absence of Merkel cell polyomavirus in combined tumors. Furthermore, the results strongly suggest fundamental biological differences between Merkel cell polyomavirus-positive and -negative Merkel cell carcinomas, supporting that Merkel cell polyomavirus plays an important role in the pathogenesis of Merkel cell polyomavirus-positive Merkel cell carcinoma.

Merkel cell carcinoma with lymphoepithelioma-like pattern: a case report of an exceedingly rare variant of merkel cell carcinoma with lymph node metastases at presentation

Merkel cell carcinoma (MCC) or primary neuroendocrine carcinoma of the skin is a rare neoplasm with aggressive behavior. Primary lymphoepithelioma-like (LEL) carcinoma of the skin is a recently described exceptional tumor, with a relatively good prognosis, and is characterized by a neoplastic epithelial component associated with a dense lymphoid stroma. Rarely, MCC shows a marked lymphocytic host response or can even mimic a LEL carcinoma. We report a new case of MCC mimicking an LEL carcinoma in a 72-year-old male; the diagnosis of MCC was made on the basis of the morphology and immunohistochemical findings. We present through this case an exceptional pattern of MCC which can be misleading, and we insist on differential diagnoses.

Merkel cell carcinoma

Merkel cell carcinoma is a rare, highly aggressive neuroendocrine cutaneous neoplasm with a variable clinical presentation. Histologically, it is a predominantly dermal-based lesion composed of monotonous small round cells with scanty cytoplasm, often difficult to differentiate from small round cell tumors, metastatic small cell carcinoma, blastic hematologic malignancies, and melanoma. The malignant cells express both epithelial and neuroendocrine immunohistochemical markers, a unique feature that helps differentiate this neoplasm from other entities. The pathogenesis of Merkel cell carcinoma has remained a mystery despite its association with various chromosomal abnormalities and with growth signaling and apoptotic pathways. The discovery of the Merkel cell polyomavirus suggests another clue to its pathogenesis. This virus integrates into band 3p14 and promotes carcinogenesis by altering the activity of tumor suppressor and cell cycle regulatory proteins. This discovery of the Merkel cell polyomavirus may greatly enhance our understanding of this rare aggressive neoplasm and allow further advancements in treatment.

Marjolin's ulcer: a preventable complication of burns?

LEARNING OBJECTIVES

After studying this article, the participant should be able to: 1. Discuss the clinical features of Marjolin's ulcer. 2. Identify the risk factors for the development of Marjolin's ulcer. 3. Develop a surgical management plan for the treatment of Marjolin's ulcer.

SUMMARY

Marjolin's ulcer is a rare and aggressive cutaneous malignancy that arises on previously traumatized and chronically inflamed skin, especially after burns. This clinical condition was first described by Marjolin in 1828. The term "Marjolin's ulcer" has been generally accepted to refer to a long-term malignant complication of the scars resulting from burns. However, vaccination, snake bites, osteomyelitis, pilonidal abscesses, pressure sores, and venous stasis may also induce this tumor. Clinically, reports suggest that atrophic and unstable scars tend to develop into cancer. Various etiological factors have been implicated in the condition, including toxins released from damaged tissues, immunologic factors, cocarcinogens, and miscellaneous factors such as irritation, poor lymphatic regeneration, antibodies, mutations, and local toxins. The incidence of burn scars undergoing malignant transformation has been reported to be 0.77 to 2 percent. All parts of the body can be affected, but the extremities and the scalp are most frequently affected. There are two variants: acute and chronic. In the former, the carcinoma occurs within 1 year of the injury. The chronic form is more frequent and malignancy tends to develop slowly, with an average time to malignant transformation of 35 years. Although many different cell types can be seen in these lesions, the major histological type is squamous cell carcinoma. Marjolin's ulcers are generally considered as very aggressive tumors with a higher rate of regional metastases; radical excision is the treatment of choice, but there is no consensus on lymph node dissection. Marjolin's ulcer can be insidious and often leads to a poor prognosis, and deaths from Marjolin's ulcer are not uncommon. Meticulous wound care is a crucial step in prevention of these lesions.

New insights into merkel cell carcinoma

Merkel cell carcinoma (MCC) is a rare aggressive cutaneous malignancy of the elderly and immunocompromised populations. The clinical presentation of MCC is nonspecific, with the majority of cases presenting as localized skin involvement. Histologically and immunophenotypically, MCC is defined by both neuroendocrine and epithelial differentiation. Recently, the Merkel cell polyomavirus has been implicated in the pathogenesis of MCC. In addition, there have been numerous studies evaluating the histologic and immunohistochemical characteristics of MCC as they relate to diagnosis and prognosis. The purpose of this paper is to review the most salient and clinically relevant updates in the pathogenesis and histologic features of MCC. Specific attention is given to the clinical and histologic predictors of prognosis, staging, and the controversies concerning sentinel lymph node biopsy and therapy.

Basal cell carcinoma with progression to metastatic neuroendocrine carcinoma

Merkel cell carcinoma (MCC) or primary cutaneous neuroendocrine carcinoma is a malignant tumor considered to demonstrate differentiation towards Merkel cells that are present at the base of the epidermis or around the apical end of some hair follicles and are thought to play a yet uncertain role in sensory transduction. Here we present the case of a 54- year old female with a basal cell carcinoma (BCC) of the skin with neuroendocrine features (positivity for chromogranin) that has evolved during multiple recurrences and radiotherapy into a high-grade neuroendocrine carcinoma with morphological and immunohistochemical features of MCC (trabecular and nesting arrangement, positivity for chromogranin, cytokeratin 20, neuron specific enolase, and also neurosecretory granules on electron microscopy). The progression from a chromogranin positive basal cell carcinoma of the skin, to a high-grade neuroendocrine carcinoma demonstrates the potential for cross differentiation among skin tumors.

Second cancers following the diagnosis of Merkel cell carcinoma: a nationwide cohort study

Merkel cell carcinoma (MCC) is a rare neuroendocrine carcinoma of the skin. MCCs and some other skin cancers, such as basal cell carcinomas, frequently harbour Merkel cell polyomavirus DNA. The purpose of the study was to investigate the frequency of second cancers following the diagnosis of MCC. We studied the incidence of second primary cancers after the diagnosis of MCC from the files of the Finnish Cancer Registry in 1979-2006. Among the 172 MCC patients identified a total of 34 second primary cancers were detected in 30 individuals after the diagnosis of MCC. Female MCC patients were diagnosed with 25 subsequent cancers (SIR, 2.35; 95% CI, 1.52-3.47; p<0.001) and male patients with 9 cancers (SIR, 2.32, 95% CI, 1.06-4.40; p<0.05). The MCC patients had an increased risk for a subsequent cancer (any site) compared to age-, gender- and calendar period-matched general population (standardized incidence ratio [SIR] 2.34; 95% confidence interval [CI], 1.62-3.27). The risks for basal cell carcinoma of the skin (O=11), SIR, 3.48; 95% CI, 1.74-6.22 and chronic lymphocytic leukemia (O=2), SIR, 17.9; 95% CI, 2.16-64.6 were significantly elevated. The SIRs for an overall second primary cancer risk did not change markedly with time since the diagnosis of MCC. We conclude that patients diagnosed with MCC have an increased risk for a second cancer. This risk may in part result from shared etiological factors between MCC and other tumour types, such as immunosuppression or possibly Merkel cell polyomavirus infection.

Merkel cell polyomavirus expression in merkel cell carcinomas and its absence in combined tumors and pulmonary neuroendocrine carcinomas

Merkel cell carcinoma (MCC) is the eponym for primary cutaneous neuroendocrine carcinoma. Recently, a new polyoma virus has been identified that is clonally integrated in the genome of the majority of MCCs, with truncating mutations in the viral large T antigen gene. We examined the presence of Merkel cell polyomavirus (MCV) in a set of 17 frozen tumor samples by quantitative polymerase chain reaction; 15 of them (88%) were positive. Sections from corresponding archival material were analyzed by immunohistochemistry (IHC) with the novel monoclonal antibody CM2B4, generated against a predicted antigenic epitope on the MCV T antigen, and tested for the expression of cytokeratin 20 (CK20). Sufficient archival material for IHC was available in only 15 of the 17 cases whose frozen tissue samples had been studied by polymerase chain reaction. Of the 15 tumors analyzed immunohistochemically, 10 (67%) showed positive labeling with CM2B4, 14 (93%) expressed CK20. A tissue microarray of 36 MCCs, 7 combined squamous and neuroendocrine carcinomas of the skin, and 26 pulmonary neuroendocrine carcinomas were also examined by IHC. Of the 36 MCCs assembled on a microarray, 32 (89%) tumors expressed CK20, and 27 (75%) were immunoreactive with CM2B4. The skin tumors with a combined squamous and neuroendocrine phenotype and all pulmonary neuroendocrine carcinomas failed to react with CM2B4. Our study shows that CM2B4 is a useful reagent for the diagnosis of MCC. It labels the majority of MCCs, but fails to react with pulmonary neuroendocrine carcinomas. We also found that neuroendocrine carcinomas of the skin arising in association with a squamous cell carcinoma seem to be independent of MCV.

Merkel cell carcinoma demographics, morphology, and survival based on 3870 cases: a population based study

BACKGROUND

Merkel cell carcinoma (MCC) is a rare and aggressive neuroendocrine tumor arising predominantly on sun-exposed skin of older and usually immunosuppressed individuals.

METHODS

Using data from NCI's SEER (Surveillance, Epidemiology, and End Results) Program from 1973 to 2006, we analyzed the demographics and survival of MCC.

RESULTS

SEER had recorded 3870 cases of MCC. The incidence was higher in men (2380 cases, 61.5%) than in women (1490 cases, 38.5%). Most patients were White (94.9%) between 60 and 85 years of age. MCC was rare in Blacks. The most common location was the head and neck. The salivary glands, nasal cavity, lip, lymph nodes, vulva, vagina and esophagus were the most common extracutaneous sites. The 10-year relative survival rate was higher in women than men (64.8% vs. 50.5%, p < 0.001). Patients 50-69 years had the highest 10-year relative survival rate (59.6%). Stage of disease was the best predictor of survival.

CONCLUSIONS

MCC arises predominantly in the skin of head and neck in White men above 70 years of age. Cases also occurred in extracutaneous sites. Age did not predict survival, yet gender, site and tumor size revealed clear differences. The most significant predictor of survival was tumor stage.

Merkel Cells, Normal and Neoplastic: An Update

Merkel cells (MC) occur in the basal epidermal layer, hair follicles, and oral mucosa, as complexes with sensory axons. The axons transduce slowly adapting type I mechanoreception, and MC modulate their sensitivity. MC also determine and maintain the 3-dimensional epidermal structure. They have neuroendocrine granules, rigid spinous processes, and desmosomal junctions with each other and with keratinocytes. Rare MC are dermaWl. Current evidence supports a basal cell origin. Merkel cell carcinomas (MCC) occur mostly in sun-exposed skin in old age. Trabecular, intermediate, or small cell in pattern, MCC have neuroendocrine granules, intercellular junctions, rigid spinous processes, and a paranuclear collection of intermediate filaments staining for cytokeratin 20. Most MCC behave indolently, but those with the small cell pattern, and some with the intermediate pattern, are aggressive and rapidly fatal.

Merkel cell carcinoma: review

Merkel cell carcinoma (MCC) is synonymous with primary cutaneous neuroendocrine carcinoma. It tends to affects elderly whites, but there is also an increased incidence among immunosuppressed patients. The recent identification of a novel polyomavirus associated with the tumor has stimulated renewed interest in its pathogenesis. MCC tends to show classic histologic features of a neuroendocrine carcinoma and is often positive for CK20, but nonclassic cytologic findings and unusual immunophenotypes may be observed and can lead to a diagnostic confusion. MCC needs to be distinguished from other primary cutaneous tumors with a small cell appearance and metastatic tumors. Surgical excision is the treatment of choice, but radiation therapy has also found to be effective. Sentinel lymph node biopsy has become an integral part of the staging of patients with MCC.

Merkel cell carcinoma with squamous and sarcomatous differentiation

Merkel cell carcinoma is an aggressive neuroendocrine tumor historically thought to arise from neural crest-derived cutaneous neuroendocrine cells. Recent evidence supports an epidermal origin. We present a case of Merkel cell carcinoma arising on the upper arm of a 94-year-old woman that had multiple morphologic patterns: small cells typical of Merkel cell carcinoma, malignant cells with squamous differentiation and malignant poorly differentiated spindle cells. Subsequent metastatic disease in regional lymph nodes showed only the small cells and the malignant spindle cells. To our knowledge, this is the first case of Merkel cell carcinoma showing these three patterns of differentiation at first presentation. This morphology raises the possibility that Merkel cell carcinomas may arise from epidermal stem cells that can differentiate along different lines.