Merkel cell carcinoma of the skin: the structure and origin of normal Merkel cells

Merkel cell carcinoma and the eye

Merkel cell carcinoma (MCC) is a rare cutaneous neuroendocrine tumor with a poor five-year survival rate. Yearly cases have risen nearly 350% since the early 1980s, and these are predicted to increase as the overall US population ages. MCC of the eyelid is uncommon and can be misdiagnosed as other benign inflammatory and neoplastic eyelid disorders. Although MCC of the head and neck is often more aggressive than it is at other sites, eyelid MCC shows a lower disease-specific mortality rate. A biopsy is essential for accurate diagnosis, including an immunohistochemical panel of CK20 and TTF-1, although other markers may be necessary. Staging can be assessed clinically through physical examination findings and imaging and/or pathologically with sentinel lymph node biopsy or fine-needle aspiration. Pathologic staging more accurately predicts the prognosis. Eyelid MCC treatments include Mohs micrographic surgery to allow for complete clearance and adequate reconstruction of lost tissue, followed by adjuvant radiotherapy. In advanced disease, immunotherapies are preferred over traditional chemotherapy and are a subject of ongoing research.

Merkel cell carcinoma of the eyelid: A review

Merkel cell carcinoma (MCC) is a rare, aggressive tumor of both epithelial and neuroendocrine origin, which carries a mortality rate of up to 40%. MCC tumors typically present as painless, expanding nodules on the sun-exposed skin areas of older, white patients. Eyelid and periocular tumors comprise approximately 2.5% of all cases of MCC and may be mistaken for chalazia or basal cell carcinomas. Immunosuppression is a significant risk factor, particularly in solid-organ-transplant recipients, patients with chronic lymphocytic leukemia, and patients with HIV. Sentinel lymph node biopsy is often used for accurate staging of head and neck MCC. Treatment includes wide local excision, commonly with the addition of radiotherapy for improved locoregional disease control. Historically, adjuvant chemotherapy had been reserved for metastatic disease, but immunotherapy and targeted chemotherapies are currently being investigated for use in primary disease. The clinical characteristics of all available published cases of eyelid MCC are summarized in this article.

18F-FDG and 68Ga-somatostatin analogs PET/CT in patients with Merkel cell carcinoma: a comparison study

BACKGROUND

Merkel cell carcinoma (MCC) is an aggressive neuroendocrine skin tumor. Currently, 18F-fluoro-deoxy-glucose (18F-FDG) PET/CT is the functional imaging modality of choice. Few data are available on the use of 68Ga-somatostatin analogs. The aim of our study was to evaluate and compare the diagnostic performance of 18F-FDG and 68Ga-somatostatin analog PET/CT in MCC patients.

RESULTS

Fifteen patients (12 males, 3 females; median age 73 years; range 41-81 years) with histologically proven MCC (4 with unknown primary lesion) who underwent both 18F-FDG and 68Ga-somatostatin analog PET/CT for staging, re-staging, or treatment response assessment were retrospectively evaluated. Results of both studies were qualitatively analyzed and compared on a patient- and lesion-based analysis, using histology or clinical/radiological follow-up as reference standard for final diagnosis. According to final diagnosis, 8/15 patients had at least one MCC lesion and 7/15 had no evidence of disease. On a patient-based analysis, 18F-FDG and 68Ga-somatostatin analogs correctly classified as positive 8/8 (100% sensitivity) patients and as negative 6/7 (85.7% specificity) and 5/7 (71.4% specificity) patients, respectively, with no significant difference. On a lesion-based analysis, 18F-FDG detected 67/75 lesions (89%) and 68Ga-somatostatin analogs 69/75 (92%), with no significant difference. In four patients with unknown primary MCC, both tracers failed to identify the primary MCC site.

CONCLUSIONS

Our preliminary data suggest that 18F-FDG and 68Ga-somatostatin analog PET/CT provide good and equivalent diagnostic performance, adding interesting insights into the complex MCC biology. However, these results do not suggest that 18F-FDG PET/CT should be replaced by 68Ga-somatostatin receptor imaging, which should be performed in addition, according to clinical indication, to the perspective of "personalized medicine."

Clinical Experience on Eight Cases of Merkel Cell Carcinoma

Merkel cell carcinoma is a rare neuroendocrine neoplasm of the skin. The tumor most frequently affects elderly patients, with a preference for the head and neck. Eight patients affected by Merkel cell carcinoma have been observed at the General Surgery Unit II of the “Istituti Ospitalieri” hospital in Cremona, each in different stages of the disease; 75% of the cases involved the extremities, and in nearly all of the cases the tumor was nodular in appearance, with an average diameter of 2.2 cm. In 2 cases, the tumor was associated with rheumatoid arthritis, suggesting a dependency on the part of the neoplasm on the immune disorder and on steroid treatment. The available data confirm that in stage I of the disease, surgical treatment should be associated with radiotherapy in order to control the development of local relapses or metastases over time. In this stage, we observed a survival of 34 months (range, 24-48). In stages II and III, survival time falls, with very short duration of responses and poor quality of life as a result of the administration of cytotoxic molecules. Bearing in mind that any local relapse tends to appear within 12 months of the removal of the primitive tumor, that lymph node metastases appear in almost half of the patients, and that metastases over time are manifested in over a third of patients, it is essential to adopt a treatment capable of balancing the demand for longer remissions with a better quality of life. In this situation, we observed that treatment with somatostatin analogues achieves interesting responses without side effects, which suggests a close biological relationship between the tumor and somatostatin and that making a careful assessment of the prognostic factors of the disease can guarantee a correct therapeutic choice.

Neuroendocrine Carcinoma of the Skin (Merkel Cell Carcinoma): Immunocytochemical Study of a Case

The immunocytochemical phenotype was evaluated in a case of Merkel cell carcinoma of the skin. Intermediate filaments, i.e. neurofilament, glial fibrillary acid protein, cytokeratins, keratin and panfilament as well as S-100 protein, calcitonin and epithelial membrane antigen were detected by immunoperoxidase methods. Nodular positivity for neurofilament was observed. The remaining intermediate filaments and other markers were negative. Thus the origin of Merkel cell carcinoma appears uncertain and this tumor probably has neuroendocrine activity.

Lymph Node Merkel Cell Carcinoma with No Evidence of Cutaneous Tumor - Report of Two Cases

We report two cases of Merkel cell carcinoma within inguinal and axillary lymph nodes, respectively, showing no clinicopathologic evidence of a primary (extranodal) tumor; one of our patients was alive with no evidence of disease five years and ten months after the surgical excision of the neoplasm with no postoperative chemotherapy.

The diagnosis of nodal Merkel cell carcinoma needs to be supported by a careful immunohistochemical study: in fact, cytokeratin- and neurofilament-positive paranuclear “dots”, as well as epithelial antigens and neuroendocrine markers may be variably expressed in tumor cells, thus requiring the application of a complete antibody panel.

In the presence of a nodal Merkel cell tumor, an exhaustive clinico-radiologic search for a primary tumor must be carried out. After the exclusion of any reasonable starting point of the neoplasm, a provisional diagnosis of “primary” nodal Merkel cell carcinoma may be acceptable; since a primary extracutaneous tumor is expected to follow a less aggressive course than a metastatic one, follow-up data may provide indications as to the truly extracutaneous origin of Merkel cell carcinoma.

Expression of Merkelcell polyomavirus (MCPyV) large T-antigen in Merkel cell carcinoma lymph node metastases predicts poor outcome

Background

The aim of this study was to determine the prevalence of MCPyV in Merkel cell carcinoma (MCC) primaries versus lymph node metastasis and to evaluate possible prognostic factors.

Methods

Samples of MCC primaries and lymph node metastases were stained immunohistochemically for the MCPyV large T-antigen and expression was compared to patients´ clinical outcome.

Results

41 MCC patients were included. 33 (61%) out of 54 specimens were MCPyV-positive in the immunohistochemistry. 15 (47%) out of 32 primary tumors were positive compared to 18 (82%) out of 22 lymph node metastases. Eleven patients with positive polyomavirus expression died from the carcinoma compared to 4 patients without virus expression. Cox regression analysis showed worse disease-free survival in patients with MCPyV compared to virus-negative lymph nodes (p = 0.002).

Conclusions

To our knowledge this is the first study to describe a negative prognostic effect of the MCPyV expression in lymph node metastasis in MCC patients.

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.

Management of Merkel cell carcinoma of unknown primary origin: the Vienna Medical School experience

Merkel cell carcinoma is a rare, but highly aggressive skin tumor. We describe our single-institution experience with the diagnosis and treatment of Merkel cell carcinoma of unknown primary (MCCUP). We conducted a retrospective medical chart review of patients treated with MCCUP at the Vienna General Hospital between 2002 and 2011. Clinicopathologic variables and outcomes were analyzed. Of the entire cohort of 57 patients, 8 patients (14%) were diagnosed with MCCUP. Three patients presented with parotid gland involvement, four patients with positive inguinal lymph nodes and one with axillar lymph nodes. CK20 staining was positive in all tumor specimens, whereas MCPyV protein was positive in four out of six patients. The primary surgical modality in five cases was wide local excision. In one patient excisional biopsy was followed by re-resection. In one case only excisional biopsy was performed due to metastatic disease at first diagnosis. Two patients underwent concomitant parotidectomy and neck dissection, and four patients received adjuvant radiation therapy. Median recurrence-free survival was 20 months. Four patients died, three of disease and one of other cause. Recurrent disease was observed in two patients and treated with radiotherapy and chemotherapy. The 1- and 3-year overall survival rates were 87.5 and 37.5%, respectively. The 1- and 3-year disease-specific survival rates were 87.5 and 62.5%, respectively. Our study shows a poor outcome in patients with MCCUP, particularly in patients with node involvement of the trunk. We therefore suggest an aggressive and multimodal treatment approach for patients with MCCUP.

Merkel cell carcinoma

Merkel cell carcinoma (MCC) is a rare, clinically aggressive cutaneous neuroendocrine neoplasm with a high mortality rate. Though the etiology is not precisely known, Merkel cell polyomavirus DNA has been found recently in a large percentage of MCC tumors. Other suggested risk factors include sun exposure, immunosuppression, and a history of prior malignancy. Work up of patients with MCC most notably includes nodal staging via clinical examination or sentinel lymph node biopsy. The prognosis for most patients with MCC is poor, and the rarity of MCC precludes the prospective, randomized clinical trials necessary to elucidate optimum treatment protocols. Most published data support the use of a multimodality approach centered around surgical excision with negative margins, sentinel lymph node biopsy to establish the presence or absence of nodal metastases, adjuvant radiothearpy to decrease the risk of recurrence, and systemic chemotherapy in the case of widespread disease.

Merkel cell carcinoma: a retrospective study on 48 cases and review of literature

Merkel cell carcinoma (MCC) is a rare and aggressive neuroendocrine tumor of the skin. Fourty-eight patients with MCC were observed at the Rare Hormonal Tumors Group of Cremona Hospital, 15 of these with unknown primary site. Due to rarity of Merkel cell carcinoma, clinical experience is generally limited. Data from our series confirm the current recommendations. Wide surgical excision must be associated with radiotherapy also in early stages in order to avoid local relapse and the rapid progression of disease. In advanced stages chemotherapy is the standard despite the short duration of responses and poor quality of life. The data of our series, characterized by a high demand for second opinion, offer some insight about the real rarity of the tumor, the difficulty of managing of disease in our country secondary to a wrong cultural approach to the problem, the indiscriminate use of molecules unnecessary and often expensive, the lack of protocols, and the presence of guidelines often ignored. This results in very poor survival associated with a very low quality of life, requiring to find the right direction towards a correct management of disease.

Extracutaneous Merkel cell carcinomas harbor polyomavirus DNA

Merkel cell carcinoma is a neuroendocrine tumor, with characteristic morphological and immunohistochemical features. Originally reported as primary carcinoma of skin, it has been described in numerous other sites such as lymph nodes, oral cavity, breast, vaginal walls, and salivary glands. Recent studies have revealed in cutaneous Merkel cell carcinomas a clonally integrated polyomavirus, named Merkel cell polyomavirus. The aim of the present study was to verify the presence of Merkel cell polyomavirus in 5 cases of primary Merkel cell carcinomas of lymph nodes and 1 case of parotid gland to investigate similarities or differences among Merkel cell carcinomas from various sites. Cases studied were 5 primary Merkel cell carcinomas in lymph nodes, 1 in the parotid gland, and 12 in the skin. Twelve cases of primary and metastatic small cell carcinoma of the lung were also investigated. Immunohistochemistry for keratin 20, chromogranin, synaptophysin, and thyroid transcription factor 1 was performed in all cases. Viral DNA was studied using polymerase chain reaction assay and the products evaluated in agarose gel and sequenced. Cytokeratin 20 and Merkel cell polyomavirus were detected in all cases of primary Merkel cell carcinoma irrespective of their site of origin. On the contrary, all cases of pulmonary small cell carcinoma were negative for both Merkel cell polyomavirus and cytokeratin 20. It appears that cutaneous and extracutaneous Merkel cell carcinomas share similar histologic, immunohistochemical, and molecular features. This is further evidence that Merkel cell carcinomas are a multiorgan carcinoma and that Merkel cell polyomavirus might play a role in the pathogenesis of this neoplasm.

[Merkel cell carcinoma revisited: a new example of viro-induced human tumour]

Merkel cell carcinoma (MCC) is a neuroendocrine carcinoma of the skin of poor outcome. A new type of virus, isolated in 2008, was found to be strongly associated with CCM. This virus, belonging to the family of polyomavirus, was called MCPyV for Merkel Carcinoma Polyomavirus. Recent data favour a causative role of MCPyV in oncogenesis. MCC represents thus a new model for the understanding of the mechanisms of oncogenesis. The distinct molecular viral signature in every case of MCC represents an original tool for the follow-up of the disease. New therapeutic perspectives are to be drawn using this model.

Primary neuroendocrine (merkel cell) carcinoma of the anterior skull base

A case of a primary neuroendocrine (Merkel cell) carcinoma arising in the anterior skull base involving the dura, both frontal lobes, and the paranasal sinuses is presented. The tumor was completely removed by an enlarged bifrontal transbasal approach. The neuropathological, immunohistological, and electron microscopical investigation revealed all characteristics of a Merkel cell carcinoma, normally presenting as a skin carcinoma of the head and neck. The history, treatment, neuropathology, and possible explanation for this rare manifestation are discussed.

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.

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.

Human Merkel cell polyomavirus infection I. MCV T antigen expression in Merkel cell carcinoma, lymphoid tissues and lymphoid tumors

Merkel cell polyomavirus (MCV) is a recently discovered human virus closely related to African green monkey lymphotropic polyomavirus. MCV DNA is integrated in approximately 80% of Merkel cell carcinomas (MCC), a neuroendocrine skin cancer linked to lymphoid malignancies such as chronic lymphocytic leukemia (CLL). To assess MCV infection and its association with human diseases, we developed a monoclonal antibody that specifically recognizes endogenous and transfected MCV large T (LT) antigen. We show expression of MCV LT protein localized to nuclei of tumor cells from MCC having PCR quantified MCV genome at an average of 5.2 (range 0.8-14.3) T antigen DNA copies per cell. Expression of this putative viral oncoprotein in tumor cells provides the mechanistic underpinning supporting the notion that MCV causes a subset of MCC. In contrast, although 2.2% of 325 hematolymphoid malignancies surveyed also showed evidence for MCV infection by DNA PCR, none were positive at high viral copy numbers, and none of 173 lymphoid malignancies examined on tissue microarrays expressed MCV LT protein in tumor cells. As with some of the other human polyomaviruses, lymphocytes may serve as a tissue reservoir for MCV infection, but hematolymphoid malignancies associated with MCC are unlikely to be caused by MCV.

Merkel Cell Carcinoma with Pagetoid Spread

A case of Merkel cell carcinoma showing epidermotropism is presented. The neoplastic cells displayed dotlike immunoreactivity for cytokeratins and strong immunoreactivity for neuron-specific enolase. Although no neuroendocrine granules were found, characteristic paranuclear fibrous bodies were present.

Merkel cell carcinoma of the skin: pathological and molecular evidence for a causative role of MCV in oncogenesis

Merkel cell carcinoma (MCC), a skin tumour with neuroendocrine features, was recently found to be associated with a new type of human polyomavirus, called Merkel cell virus (MCV). We investigated the specificity of this association as well as a causal role of MCV in oncogenesis. DNA and RNA from ten cases of MCC were analysed using PCR and RT-PCR. DNA from 1241 specimens of a wide range of human tumours was also analysed. The DIPS technique was used to identify the integration locus of viral DNA sequences. Array CGH was performed to analyse structural alterations of the cell genome. MCV DNA sequences were found in all ten cases of MCC and in none of the 1241 specimens of other tumour types. Clonal integration of MCV into the host genome was seen in all MCC cases and was checked by FISH in one case. A recurrent pattern of conserved viral sequences which encompassed the replication origin, the small tumour (ST), and the 5' part of the large tumour (LT) antigen DNA sequences was observed. Both ST and LT viral sequences were found to be significantly expressed in all MCCs. Neither recurrent site of integration nor alteration of cellular genes located near the viral sequences was observed. The tight association of MCV with MCC, the clonal pattern of MCV integration, and the expression of the viral oncoproteins strongly support a causative role for MCV in the tumour process. This information will help the development of novel approaches for the assessment and therapy of MCC and biologically related tumours.

Trisomy of chromosome 6 in Merkel cell carcinoma within lymph nodes

Merkel cell carcinoma (MCC) of the skin is a neuroendocrine tumor with characteristic histological and immunohistochemical features. Among various cytogenetic changes, trisomy of chromosome 6 has been reported in 47% of cases using in situ hybridization. Primary tumors, morphologically and immunohistochemically identical to MCCs of the skin, have been described in other organs, including lymph nodes. Here, a cytogenetic study of four cases of MCC of lymph nodes is presented. Four cases of primary MCCs of lymph nodes and ten cases of cutaneous MCCs were studied for chromosome 6 using fluorescent in situ hybridization (FISH). All cases showed typical features of MCC both at hematoxylin and eosin (H&E) and immunohistochemistry. FISH showed trisomy 6 in two out of the four cases ofMCCs of lymph node as well as in 6 out 10 cases of MCCs of skin. Lymph nodal and cutaneous MCCs share same histological and immunohistochemical features, as well as same cytogenetic alteration for chromosome 6. It seems that there are more similarities than differences between cutaneous and lymph nodal MCCs. Whether lymph nodal MCCs are primary tumors or metastases from regressed skin lesions is still questionable, although several findings indicate a primary origin.

Vascular changes in merkel cell carcinoma based on a histopathological study of 92 cases

Although prominent vascular proliferation is a known feature of various neuroendocrine tumors, it has not been systematically studied in Merkel cell carcinoma (MCC) of the skin. The purpose of this study was to fully characterize the light microscopic, immunohistochemical, and ultrastructural features of vascular changes associated with MCC and to determine their frequency and differential diagnostic implications. Additionally, the presence of human herpesvirus 8 DNA in the lesional tissue was investigated. Of 92 studied cases of MCC, 18 cases (20%) were found to exhibit foci of prominent vascular changes which were classified into the following 6 patterns: pericyte hyperplasia, pyogenic granuloma-like, hemangioendothelioma-like, epithelioid hemangioma-like, peliosis-like, and follicular dendritic cell tumor-like pattern. In addition, Azzopardi phenomenon was observed. These changes occurred singly or in combination. Human herpesvirus 8 DNA was identified by polymerase chain reaction in none of the 18 cases. It is concluded that prominent vascular proliferations may be seen in 20% of MCC, and thereby, MCC resembles neuroendocrine tumors in other organs. When unduly prominent and encountered in a limited biopsy specimen, vascular alterations may represent a potential diagnostic pitfall, but, on the other hand, they themselves may serve as a clue to the correct diagnosis. Human herpesvirus 8 does not play a role in angiogenesis in MCC.

A comprehensive review of the treatment of Merkel cell carcinoma

Merkel cell carcinoma (MCC) is an uncommon but malignant cutaneous neuroendocrine carcinoma with a high incidence of local recurrence, regional lymph node metastases, and subsequent distant metastases. The etiology of MCC remains unknown. It usually occurs in sun-exposed areas in elderly people, many of whom have a history of other synchronous or metachronous sun-associated skin lesions. The outcome for most patients with MCC is generally poor. Surgery is the mainstay of treatment. The role of adjuvant therapy has been debated. However, data from recent development support a multimodality approach, including surgical excision of primary tumor with adequate margins and sentinel lymph node dissection followed by postoperative radiotherapy in most cases, as current choice of practice with better locoregional control and disease-free survival. Patients with regional nodal involvement or advanced disease should undergo nodal dissection followed by adjuvant radiotherapy and, perhaps, systemic platinum-based chemotherapy in most cases.

Merkel Cell Carcinoma of the Eyelid

PURPOSE

To evaluate the clinical and histopathologic characteristics of Merkel cell carcinoma (MCC) of the eyelid.

DESIGN

Retrospective case series and literature review.

PARTICIPANTS

Three consecutive patients with MCC of the eyelid who were referred to the Ocular Oncology Unit of Leiden University Medical Center, Netherlands.

METHODS

Clinical records and histopathologic material of patients with eyelid MCC were reviewed. The clinical presentation and treatment were evaluated.

MAIN OUTCOME MEASURES

Clinical and histopathologic description of eyelid MCC, with histologic proof of spontaneous regression of the tumor.

RESULTS

Three patients with MCC of the eyelid were included. Diagnosis was made by pathologic investigation and immunohistochemistry (S100, cytokeratin 20, epithelial membrane antigen, chromogranin). Two of the patients showed histologically proven complete spontaneous regression after nonradical excision of the tumor. After local excision, none of the MCCs demonstrated local recurrence, without regional or distant metastases. Mean clinical follow-up was 50 months.

CONCLUSIONS

Nonocular MCC is known to recur in 66% of patients and to be lethal in almost 33%. Merkel cell carcinoma of the eyelid is a rare malignancy that can not be recognized clinically. Clinical differential diagnosis must be made with a chalazion, and histopathologic differential diagnosis must be made with small cell carcinomas. Close follow-up of these patients is advised because of the potential high recurrence rate and lymphatic spread. The immunologic phenomenon of spontaneous regression points out the importance of the immune system in this disease.

p63 expression as a new prognostic marker in Merkel cell carcinoma

BACKGROUND

Merkel cell carcinoma (MCC) is an aggressive neuroendocrine skin tumor, mostly affecting elderly individuals. The histogenesis of this rare tumor as well as its prognostic criteria are a matter of dispute.

METHODS

An immunohistochemical analysis of markers of proliferation (Ki-67/MIB-1), neuroendocrine differentiation (chromogranin A and synaptophysin), and basal cell differentiation (p63) was performed in a series of 47 cases of MCC. The significance of pathologic data and of immunoreactivity with different markers was evaluated using the chi-square test. Survival curves were calculated using the Kaplan-Meyer method. The survival difference was estimated using the Wilcoxon or Mantel-Cox test.

RESULTS

Immunohistochemical evidence of neuroendocrine differentiation and immunopositivity for cytokeratin 20 were observed in all cases, whereas positivity for p63 was detected in approximately half of the cases (25 of 47 cases; 53.2%). Cases that were positive for p63 demonstrated a more aggressive clinical course than those that were negative (Z value of 2.93; P = .0003; hazards ratio of 22.22).

CONCLUSIONS

Data from the current study indicate that p63 expression is associated with a worse prognosis in patients with MCC and represents a new independent marker of clinical evolution.

The Toker Tumor

Primary neuroendocrine carcinoma of the skin is a relatively rare tumor that was first described by Cyril Toker in 1972. Since the seminal paper by Toker based on simple morphologic observations and detailed clinical correlation, our understanding of the clinical, morphological, and biological attributes of these lesions has grown exponentially with their increased awareness by pathologists and clinicians as well as with the many contributions of modern diagnostic techniques. The present review focuses principally on the various morphologic appearance that these tumors are able to adopt, the role of modern special techniques for diagnosis, and the conditions that need to be considered in their differential diagnosis.

Merkel cell carcinoma: a report of 34 cases and literature review

BACKGROUND

Merkel cell carcinoma (MCC) is a rare and aggressive skin cancer, with unclear histogenesis. To date there is no consensus on the optimal treatment of this neoplasm, with controversy surrounding the use of radiotherapy and chemotherapy. There are also limited data on biological behaviour and prognosis, with reported survival ranging from 31% at three years to 74% at five years.

METHOD

The medical records of 34 patients with a diagnosis of primary MCC, treated at two NHS trusts in Birmingham and Coventry, were reviewed. An extensive review of the English literature was also performed.

RESULTS

MCC occurred predominantly in Caucasians (97%) with a mean age of 75 years. Identified risk factors were a previous history of SCC (37%), BCC (18%) and AK (20%). Ten percent of patients showed evidence of immunocompromise. Most tumours were located on the extremity, where they reached a mean size of 2.1cm. Fifty percent had regional metastasis during the course of their disease. A sub group analysis of the excision margins showed that a 2-cm excision margin, extending to the deep fascia, resulted in a 50% incomplete excision rate and a 33% local recurrence rate. In contrast a 3-cm margin including deep fascia resulted in no incomplete excisions and a 10.5% local recurrence rate Prognosis was poor with a 40% 3-year survival. Combining the data from two trusts has produced a relatively large series and highlighted differences in patient characteristics and management between the units. We advocate a 3-cm excision margin, including fascia wherever possible, combined with post-operative radiotherapy to offer the best chance of local control. Survival is fairly dismal and in keeping with the aggressive nature of this tumour. The respective roles of radiotherapy and chemotherapy remain controversial.

Merkel cells in the oral mucosa

Ninety-eight consecutive surgical biopsies of oral mucosa from 96 patients were evaluated immunohistochemically with an anti-cytokeratin 20 (CK 20) anti-body to evidence Merkel cells (MC). Fifteen cases, showing the highest number of MC, were additionally studied with chromogranin A, S-100 protein, neuro filaments, epithelial membrane antigen, and double immunostaining for CK 20 and Ki67 antibodies to evaluate MC proliferation. Electron microscopy was performed in 2 cases. MC were observed in 58 cases. The highest number of MC was found in the gingival, buccal, and palate mucosa, especially in chronically damaged oral mucosa (lichen and chronic aspecific inflammation) as well as in the mucosa overlying tumors rather than in normal or acute inflammation. MC were not observed in dysplastic or neoplastic epithelium. MC showed evidence of proliferation, as demonstrated by Ki67 positivity, in 3 cases. In conclusion, MC appear to play a role in the reparative processes of oral mucosa.

Merkel cell cancer of the skin

Merkel cell carcinoma (MCC) is a rare malignant cutaneous tumor of the elderly with rapidly growing skin nodules found predominantly on sun-exposed areas of the body. The vast majority of patients present with localized disease, while up to 30% have regional lymph node metastases. Despite local excision and the incidence of local recurrence, regional lymph node metastases and distant metastases is high and usually occurs within 2 years of primary diagnosis. The optimal treatment for patients with MCC remains unclear. The best outcome is achieved with multidisciplinary management including surgical excision of primary tumor with adequate margins and post-operative radiotherapy (RT) to control local and regional disease. Patients with regional nodal metastases should be treated with lymph node dissection plus RT. Adjuvant chemotherapy (CT) should be considered as part of the initial management. In case of metastatic disease CT based on regimens used for small-cell lung cancer is the standard treatment of care.

Merkel cell carcinoma

Background

Merkel cell carcinoma (MCC) is an unusual primary neuroendocrine carcinoma of the skin. MCC is a fatal disease, and patients have a poor chance of survival. Moreover, MCC lacks distinguishing clinical features, and thus by the time the diagnosis is made, the tumour usually have metastasized. MCC mainly affects sun-exposed areas of elderly persons. Half of the tumours are located in the head and neck region.

Methods

MCC was first described in 1972. Since then, most of the cases reported, have been in small series of patients. Most of the reports concern single cases or epidemiological studies. The present study reviews the world literature on MCC. The purpose of this article is to shed light on this unknown neuroendocrine carcinoma and provide the latest information on prognostic markers and treatment options.

Results

The epidemiological studies have revealed that large tumour size, male sex, truncal site, nodal/distant disease at presentation, and duration of disease before presentation, are poor prognostic factors. The recommended initial treatment is extensive local excision. Adjuvant radiation therapy has recently been shown to improve survival. Thus far, no chemotherapy protocol have achieved the same objective.

Conclusion

Although rare, the fatality of this malignancy makes is important to understand the etiology and pathophysiology. During the last few years, the research on MCC has produced prognostic markers, which can be translated into clinical patient care.

Cytokeratin 20 confirms merkel cell metastasis to stomach

Merkel cell carcinoma (MCC) is an uncommon, aggressive neuroendocrine carcinoma of the skin. Its prognosis is poor because of involvement of regional lymph nodes and metastases to distant sites such as bone, liver, lung, and brain. Very few metastases are reported to the gastrointestinal tract. Several studies have shown the utility of cytokeratin 20 to differentiate MCC from other small round blue cell tumors, particularly those with neuroendocrine differentiation. In this case report, we present an unusual metastasis to the stomach and the utility of cytokeratin 20 immunohistochemistry to confirm MCC.

Three-dimensional reconstruction of vessel distribution in benign and malignant lesions of thyroid

In order to better understand the spatial distribution of thyroid vessels, a series of benign and malignant thyroid lesions were studied with three-dimensional (3D) histological stereomicroscopic reconstruction. Cases consisted of normal autoptic thyroids (n=6), colloid goitres (n=6), Basedow's disease (n=2), follicular adenoma (FA) (n=4) one of which with Hurthle cells (HC), minimally invasive, well-differentiated follicular carcinoma (FTC) (n=1), well-differentiated FTC with HC (n=1), poorly differentiated FTC (n=13) with extensive angioinvasion, papillary carcinoma (PTC) (n=8) and medullary carcinoma (MTC) (n=1). From each selected nodule, parallel sections were obtained for 3D reconstruction and for histological and immunohistochemical studies. In normal thyroid, large vessels were located at the periphery of the gland with smaller branches present within the thyroid parenchyma that encircled follicles. The same pattern of vascularisation is maintained in lesions showing a follicular architecture as colloid goitre, Basedow's disease, FA, well-differentiated FTC and the follicular variant of PTC. Neoplastic lesions, at variance with non-neoplastic lesions, contained rare anastomoses. Poorly differentiated FTC and MTC contained large intratumoural vessels surrounding avascular areas corresponding to solid neoplastic cellular sheets with necrosis. PTC were more vascularised and contained numerous vascular anastomoses. In conclusion, the present data indicate that the vascular distribution is related to the follicular, papillary or solid type of growth. Vascular anastomoses and intratumoural vessels surrounding solid avascular areas are signs of malignancy.

A Case of Intraepidermal Merkel Cell Carcinoma within Squamous Cell Carcinoma In-Situ: Merkel Cell Carcinoma In-Situ?

We report a case of a 79-year-old Caucasian male who presented with a wrist lesion of combined intraepidermal Merkel cell carcinoma and squamous cell carcinoma in-situ. The two tumors were tightly admixed and distinct, and both were without any dermal or invasive components. No features of transition between the two tumors were seen. We suggest the term Merkel cell carcinoma in situ for tumors that demonstrate exclusive intraepidermal proliferation of neuroendocrine cells.

Proneural and proneuroendocrine transcription factor expression in cutaneous mechanoreceptor (Merkel) cells and Merkel cell carcinoma

Merkel cells form part of the peripheral neuroendocrine system of the skin and act as mechanoreceptors in touch response. Merkel cell carcinoma (MCC) is a rare, aggressive disease with similarities to small cell lung cancer (SCLC), which is also of neuroendocrine origin. We previously identified a novel DNA binding protein complex specific for MCC suspension cell lines, termed Merkel nuclear factor (MNF) by its binding to the POU-IV family DNA binding consensus sequence. Here we report that MNF contains the POU-IV family member Brn-3c and that Brn-3c is expressed in normal Merkel cells. Additionally, Brn-3c protein reactivity is restricted to a subset of MCC biopsies and is not seen in biopsies revealing adherent, variant cell lines lacking neuroendocrine markers. Recently, proper development of murine Merkel cells was shown to require the proneural basic helix-loop-helix transcription factor, atonal family member, MATH1. We demonstrate a correlation between Brn-3c and HATH1 reactivity in MCC biopsies and cell lines with retention of neuroendocrine phenotype. In SCLC, the related basic helix-loop-helix transcription factor HASH1 is responsible for neuroendocrine phenotype, but HASH1 transcripts were not detected in MCC cell lines. We propose that HATH1 and Brn-3c may form a transcriptional hierarchy responsible for determining neuroendocrine phenotype in Merkel cells and that lack of Brn-3c and/or HATH1 in MCC may indicate a more aggressive disease requiring closer patient follow-up.

Diagnosis and management of uncommon cutaneous cancers

Uncommon types of cutaneous cancers are mainly cited in the literature as case reports and their etiology, pathogenesis and prognosis have to be surmised because of their rarity. Within this group exist the rare and also the unusual, for instance a relatively common carcinoma arising in a strange circumstance. Initial management of such tumors involves taking a history and performing a thorough examination, allowing a diagnosis to be made. These tend to follow one of three patterns: the lesion is confidently recognized; the lesion is unknown but a likely diagnosis can be made and; the lesion is unknown. It is within the latter two groupings that the uncommon cutaneous cancers exist. A biopsy is then performed to confirm the diagnosis. For large lesions a punch or incisional biopsy is taken which must include a portion of normal skin at the lesion edge. If the lesion is small enough to allow direct closure, an excision biopsy is performed, with a minimum margin of 2mm. Shave biopsy can be employed to confirm a diagnosis, but care must be taken that the subsequent management of the lesion is not adversely affected. With the rare tumors diagnosis can be difficult and there may not be enough tissue in a biopsy for a definitive diagnosis. The whole lesion may therefore need to be excised to obtain a confident diagnosis with further surgical treatment planned as required. Once the diagnosis is established a decision on the method of treatment can be made. The limited literature would suggest that rare skin tumors are unresponsive to radiotherapy and chemotherapy, so the mainstay of treatment is surgery. When there are no established guidelines for the treatment of a particular rare tumor a pathologist can usually provide advice as to the probable nature of the lesion. This allows surgical treatment to be positioned into one of three main groups: lesions that behave like basal cell carcinomas (BCC); lesions that behave like squamous cell carcinomas (SCC) and; lesions that behave like soft tissue sarcomas (STS). It is helpful to have a management plan into which each variety of rare tumor can be fitted, giving guidance as to the best and most appropriate management. Grouping treatment into BCC, SCC or STS-like treatment has been useful. As more becomes known regarding these malignancies their subsequent management can be adjusted accordingly. Currently, it would appear wise to treat each under a broader subgroup.

Imaging of Merkel cell carcinoma

Merkel cell carcinoma (MCC) is a rare, highly malignant cutaneous tumor, primarily of the head and neck, that requires timely diagnosis, adequate staging, and aggressive therapy. MCC tends to be overlooked in the early stage, has a high propensity for invading local and regional nodal basins, and exhibits a high postoperative recurrence rate, with distant thoracic, abdominal, and central nervous system metastases. Conventional radiography and cross-sectional imaging show lesions similar to those originating from other small cell carcinomas. Nuclear medicine procedures such as sentinel node scintigraphy, somatostatin receptor scintigraphy, and positron emission tomography may be used to supplement judicious cross-sectional imaging evaluation, thereby adding diagnostic value in staging and providing therapeutic guidance. Ultimately, however, the diagnosis relies exclusively on pathologic findings at immunohistochemical staining and electron microscopy. The rarity of MCC and the resulting insufficient awareness of this neoplasm often delay correct identification and treatment, which essentially consists of wide-margin surgical excision of the primary tumor and local and regional radiation therapy. To date, clinical information is still insufficient to fully appreciate the role of imaging in MCC management. A better imaging algorithm is expected with increased awareness and improved clinical understanding of this uncommon skin neoplasm.

Merkel Cell Carcinoma: Important Aspects of Diagnosis and Management

Merkel cell carcinoma (MCC) is a highly aggressive primary neuroendocrine tumor. It is suggested in the literature that postoperative radiotherapy may decrease local recurrence and improve overall survival. The purpose of this retrospective review was to determine our experience and review the literature on this aggressive malignancy. Charts of ten patients with MCC seen between 1985 and 1997 were reviewed to obtain clinicopathological data. Eight patients were male with a mean age of 72 years (range 49–90). The head and neck was the most common site, affecting 50 per cent of patients. All patients had primary excisions with documented negative margins. Pathological size ranged from 10 to 40 mm. Initial pathological diagnosis was lymphoma in three cases requiring immunohistochemistry for cytokeratin and neuron-specific enolase for definitive diagnosis. Lymphatic invasion was noted in three patients but only one of these patients had clinical lymph node involvement. The mean follow-up was 54 months (range 6–114) with an 80 per cent one-year survival and 30 per cent 2-year survival. Postoperative radiotherapy was administered to five patients. Of these three died with evidence of both local and distant recurrence. This small retrospective review highlights important points in the management of MCC including pathological diagnosis and benefits of adjuvant radiation therapy.

Management of Merkel cell carcinoma

Merkel cell carcinoma is an uncommon cutaneous malignancy. Although it is rare, Merkel cell carcinoma has been described as the most malignant primary skin tumor. It is therefore important that once diagnosed, Merkel cell carcinoma is treated appropriately. The aim of this short review is to provide a summary of the available literature to guide clinicians in the future management of such patients. Inevitably in such a rare disease, there are no randomized trials of therapy. The treatment of individual patients will rely on opinion as much as the 'evidence'.

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

A significant proportion of primary neuroendocrine cell carcinomas of the skin (Merkel cell carcinomas [MCCs]) have been reported to occur in intimate association with malignant epithelial neoplasms, mainly squamous cell carcinomas. In addition, divergent differentiation within these tumors, particularly of squamous and eccrine types, is not infrequent. This expanded morphologic spectrum of MCC calls for evaluation of potential biologic implications of the phenotypic diversity and begs reconsideration of the histogenesis of the lesion. The current retrospective review of 29 cases of primary cutaneous neuroendocrine cell carcinoma aims to address these issues by integrating new information with that which is extant. Eleven tumors were associated with evolving or established cutaneous carcinomas: 2 actinic keratoses, 5 Bowen's disease, 3 superficial squamous cell carcinomas, and 1 basal cell carcinoma. Two combined squamous-neuroendocrine tumors occurred in recipients of solid organ transplants, and another developed in a Marjolin's ulcer at the site of a previous burn. Squamous and/or adnexal differentiation within the dermal component of the tumor was observed in 4 instances and was significantly associated with MCCs in intimate association with another cutaneous carcinoma. The outcome of the group as a whole is similar to that recorded in previous series of MCC, with local recurrence in 32% of cases and death caused by the neoplasm in 28%. Only 52% of the patients were alive with no history of metastasis at follow-up. No significant difference in outcome was observed between the patients with pure MCCs and those with MCCs in combination with another cutaneous carcinoma.

Trisomy 6 in Merkel cell carcinoma: a recurrent chromosomal aberration

We retrospectively investigated 17 cases of primary and metastasizing Merkel cell carcinomas (MCC) from 14 patients using chromosomal in-situ hybridization (CISH) to study the occurrence of trisomy 6 in these lesions.

METHODS AND RESULTS

Histological diagnosis on all tumour samples was obtained on haematoxylin and eosin stained sections. Immunohistochemistry was performed with antibodies against pancytokeratin (CAM 5.2), cytokeratin 20 (CK20), MIC2 antigen (CD99), neuron-specific enolase (NSE), and chromogranin A (chrA). Sections (4 microm) of the paraffin-embedded tumours were analysed with alpha-satellite centromeric probes for chromosome 6 or 17 using CISH. The signal was amplified by the Tyramide Signal Amplification (TSA) assay. Immunohistochemically, the tumours showed the same general epithelial neuro-endocrine pattern: 11/13 expressed cytokeratin 20, and 47% exhibited trisomy 6, with no significant difference between primary and metastatic lesions. Incomplete follow-up data did not allow us to establish a prognostic value of trisomy 6, however, this aberration might be an additional diagnostic tool in distinguishing MCC from other small round blue cell tumours.

CONCLUSIONS

CISH seems to be a promising adjunctive method to diagnose Merkel cell carcinoma. Trisomy 6 should be investigated more closely in these cases, as has been done for chromosomes 1 and 11. Of particular interest would be identification of modifications in proto-oncogene(s) located on chromosome 6.

Diagnostic relevance of chromosomal in-situ hybridization in Merkel cell carcinoma: targeted interphase cytogenetic tumour analyses

AIMS

To resolve the conflicting diagnoses of five pathologists (which included well-differentiated neuroendocrine carcinoma, malignant carcinoid, undifferentiated small-cell carcinoma, primitive neuroectodermal tumour, metastases of small-cell lung carcinoma (SCLC) and Merkel cell carcinoma (MCC)), and tumour-free lungs after necropsy, we investigated an alarmingly metastasizing MCC in a 32-year-old Caucasian man using chromosomal in-situ hybridization (CISH). Differences in incidence and course in males and females also prompted targeted analyses for chromosomes X and Y. The lesion was also analysed for p53 gene mutations.

METHODS AND RESULTS

Paraffin sections of the thorax, buccal lymph nodes and scalp tumours were stained with haematoxylin and eosin. Immunohistochemistry was performed with antibodies against pancytokeratin, keratin 20, neuron-specific enolase (NSE), chromogranin, neurofilaments and vimentin, among others. Sections (5-6 microm) of the tumours were analysed with alpha-satellite probes for chromosomes 1, 6, 7, 11, 12, 17, 18, X and Y using CrSH; and exons 5-9 of the p53 gene were examined by polymerase chain reaction and single strand conformation polymorphism (PCR-SSCP) methods. Although positive for pancytokeratin, keratin 20, chromogranin, NSE, synaptophysin and vimentin, the similarity in antigen profiles expressed by SCLC and MCC prevented a definitive tumour diagnosis. Chromosomal in-situ hybridization, however, revealed trisomies 1 and 11, two frequent aberrations in MCC, and trisomy 18. Moreover, 71% of the tumour cells had two to three copies of X, whereas 98% of the cell nuclei in the hair follicles and normal epidermis (purported Merkel cell origins) displayed one X chromosome. No mutations were detected in the five exons of the p53 gene examined.

CONCLUSIONS

Had CISH been performed earlier, treatment may have been tailored specifically to suit MCC, since MCC and SCLC have different therapeutic strategies. Finally, chromosome X may be of prognostic relevance in MCC, which apparently predominates in females and yet shows poorer prognosis in males, and hence be worthy of further investigation.

Mixed Merkel cell carcinoma and squamous cell carcinoma of the skin

Four mixed Merkel cell and squamous cell carcinomas of the skin are described. The patients ranged in age from 74 to 90 years and demonstrated or had a history of previous ultraviolet or infrared damage to the skin, manifested by basal cell carcinoma, squamous cell carcinoma, actinic keratoses, solar elastosis, and erythema ab igne. Light microscopic examination of all 4 cases revealed invasive neoplasms consisting of 2 distinct but admixed cell types. The predominant cell type was consistent with Merkel cell carcinoma and was characterized by scant cytoplasm, a small dark polygonal nucleus with granular chromatin, a high mitotic rate, and cytokeratin 20 positivity. In each case, the Merkel cell component merged with a cytokeratin 20 negative squamous component characterized by abundant eosinophilic cytoplasm, intercellular bridges, and keratinization with focal squamous pearl formation. Immunohistochemical staining patterns were consistent with the usual pattern for that cell type; transitional cells were not demonstrated. The intimate admixture of the 2 antigenically different neoplastic cell types, and common etiologic role of ultraviolet and possibly infrared damage, lend support to the theory that some Merkel cell carcinomas and squamous cell carcinomas may arise from a pluripotent epidermal stem cell.