Merkel cell tumor of the skin: an immunohistochemical study

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 lower lip: A case report and literature review

Merkel cell carcinoma (MCC) is an aggressive primary cutaneous neuroendocrine carcinoma that predominantly affects the sun-damaged skin of the head and neck region, extremities, and trunk of white older individuals. Microscopically, small to intermediate round blue cells show granular nuclei with a salt-and-pepper chromatin pattern, and are usually positive for epithelial and neuroendocrine markers, particularly for cytokeratin 20 in a perinuclear dot-like staining. The 5-year overall survival rate for individuals with localized MCC is 51% and the most common treatment choice is surgery with adjuvant radiotherapy. As far as we know, 23 cases of MCC of the lips have been reported to date in the English-language literature. We herein contribute by reporting a case of MCC affecting the lower lip of an 81-year-old male patient from Rio de Janeiro, Brazil, which likely represents the first reported case from Latin America. A review of the current literature is also included in an effort to familiarize providers with this rare, but potentially lethal neuroendocrine tumor.

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.

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.

[Merkel cell carcinoma: cutaneous manifestation of a highly malignant pre-/pro-B cell neoplasia? : Novel concept about the cellular origin of Merkel cell carcinoma]

Merkel cell carcinoma (MCC) is a relatively rare but highly malignant non-melanoma skin cancer of the elderly and immunosuppressed patients. The discovery of the Merkel cell polyomavirus (MCPyV) in 2008 significantly impacted the understanding of the etiopathogenesis of MCC. MCPyV is clonally integrated into the MCC genome and approximately 80% of MCC are MCPyV-positive. Recent results of clinical trials using blockade of the PD-1 immune modulatory pathway are promising for the future treatment of MCC. Despite this major progress of the past few years, the cellular origin of MCC still remains obscure. Based on histomorphology, gene expression profiling, and molecular analyses, we have recently hypothesized that MCC originates from pre‑/pro-B cells. Here we review putative cells of MCC, including Merkel cells, (epi‑)dermal stem cells, and pro‑/pre-B cells. In the present work, the focus is on the concept of pre‑/pro-B cells as the cellular origin of MCC, which might also impact the understanding of other human small cell malignancies of unknown cellular origin, such as small cell carcinomas of the lung and other anatomical locations. In addition, this concept might pave the way for novel treatment options, especially for advanced MCC.

Merkel Cell Carcinoma of the Buccal Mucosa and Lower Lip

Merkel cell carcinoma (MCC) is an uncommon relatively aggressive neuroendocrine dermal neoplasm first described in 1972 as a tumor of the sun exposed skin. Although most MCC affect the skin of the head and neck, rare primarily oral mucosal cases have been documented. Merkel cells are nondendritic neuroendocrine cells that are found not only in the skin but also the oral mucosa and give rise to MCC. Neuroendocrine cells may be found as aggregates in organs or as diffuse or isolated cells within organs and their epithelial lining. They contain peptide hormones and biogenic amines and occur in two forms: dendritic, which are not associated with nerve fibers and non-dendritic, which are associated with nerve fibers. Merkel cells as well as MCC express simple epithelium-type Cytokeratins (8, 18, 19, 20), neurosecretory substances; chromogranin A, synaptophysin, neuron-specific enolase (NSE), adhesion molecules, and villin (intermediate filament). Though weakly, they also express neural markers such as S-100 protein. Cytokeratin 20, and Cluster of differentiation 56, are the two key diagnostic markers for Merkel cells and MCC. Etiology includes UV radiation, the recently described Merkel cell polyomavirus, and long term systemic immunosuppression. The cutaneous and mucosal variants of MCC are considered aggressive tumors with a high risk for local recurrence and metastasis and should be considered in the differential diagnosis of head and neck mucosal lesions. We present two cases of primary Merkel cell carcinoma, one on the buccal mucosa and the other on the lower lip, and discuss the salient histologic, immunohistochemical and clinical features.

Merkel cell carcinoma: An algorithm for multidisciplinary management and decision-making

Merkel cell carcinoma (MCC) is a rare and aggressive neuroendocrine tumor of the skin. Therapeutic approach is often unclear, and considerable controversy exists regarding MCC pathogenesis and optimal management. Due to its rising incidence and poor prognosis, it is imperative to establish the optimal therapy for both the tumor and the lymph node basin, and for treatment to include sentinel node biopsy. Sentinel node biopsy is currently the most consistent predictor of survival for MCC patients, although there are conflicting views and a lack of awareness regarding node management. Tumor and node management involve different specialists, and their respective decisions and interventions are interrelated. No effective systemic treatment has been made available to date, and therefore patients continue to experience distant failure, often without local failure. This review aims to improve multidisciplinary decision-making by presenting scientific evidence of the contributions of each team member implicated in MCC management. Following this review of previously published research, the authors conclude that multidisciplinary team management is beneficial for care, and propose a multidisciplinary decision algorithm for managing this tumor.

Merkel cell carcinoma: a systematic review of ENT presentations

The aim of this study was to perform a systematic literature review of Merkel cell carcinomas (MCCs) originating exclusively in the ear, nose and throat (ENT) district. An appropriate string was run on PubMed to retrieve articles dealing with ENT presentations of MCC. A double cross-check was performed on citations and full-text articles found using the selected inclusion and exclusion criteria. In total, 43 articles were finally included in the study, describing 51 cases of MCC involving the ENT region: 22/51 (43%) cases involving the ear; 20/51 (39%) cases involving the mucosal sites; 9/51 (18%) cases involving other ENT regions. Patients with mucosal site involvement showed a higher mortality rate from the disease (45%) in comparison with the other two groups, especially when compared with those patients having primary involvement of the ear (22%). The ENT specialist should suspect and consider MCC, especially in elderly patients presenting with a suspicious lesion of the auricular pavilion, so as to avoid misdiagnosis and delayed treatments.

Role of mucins in the skin during benign and malignant conditions

Skin-related diseases comprise a major health challenge to the practicing physician, and constitute a significant psychological, social and financial burden to the society. Further, skin cancer, especially non-melanoma skin cancer is currently the leading type of malignancy in the Western world. Given the huge burden of skin diseases, there is growing emphasis on understanding their pathophysiology, and towards their early detection. Mucins are high-molecular weight O- and N-linked glycoproteins that have emerged in recent years as important molecules in maintaining health and in promoting or protecting against inflammation and cancer. They have also begun to emerge as highly specific diagnostic and prognostic markers and novel therapeutic targets in several malignant disorders. However, their role in cutaneous pathologies has remained largely obscured. The present review provides the expression patterns and proposed role of mucins in the healthy skin and various benign and malignant skin diseases. The review has immense clinical significance as the availability of highly specific reagents including monoclonal antibodies against mucins makes them extremely attractive targets for specific diagnosis and/or immunotherapy of benign and malignant cutaneous diseases.

Bilateral primary Merkel cell carcinoma of the upper lid misdiagnosed as Basal cell carcinoma

Merkel cell tumour is a rare primary malignant tumour of the skin that can affect the lids and periocular region. It has a high rate of recurrence and metastasis following surgical excision and an overall mortality rate of 20-33%. Clinically, it is difficult to distinguish from other malignancies and the diagnosis requires careful histological analysis and immunocytochemical staining. A case of Merkel cell tumour affecting the lids and originally misdiagnosed is presented. Correct diagnosis was made only after the appearance of a second Merkel cell tumour on the contralateral lid. The pathogenesis, clinical progression, histology and management of this difficult condition are reviewed.

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.

Merkel cell carcinoma of the tongue and head and neck oral mucosal sites

Merkel cell carcinoma (MCC) is an uncommon primarily dermal malignancy of relatively aggressive biologic course. Several presentations in the mucosa of the head and neck region have been reported in the literature, and 3 such patients have recently been seen at our institution. We review this recent experience and present the first reported primary lingual MCC in a 57-year-old caucasian man. We provide a review of oral mucosal MCC and guidelines for histopathologic and immunohistochemical diagnosis. Merkel cell carcinoma should be included in the differential diagnosis of head and neck mucosal lesions, especially if the tumor is submucosal, and MCC may involve the tongue. Mucosal MCC is aggressive, and there is a high risk for local recurrence and regional and distant metastasis. Fulminating courses are often seen. We discuss our treatment policies based on the current literature.

Immunohistochemistry in diagnostic dermatopathology

This article briefly reviews many immunohistochemical stains that have been in use for years, emphasizing their diagnostic use and potential pitfalls. Several newer immunostains are described in a more comprehensive fashion, including brief summaries from recently published studies.

Cytokeratin and neurofilament protein staining in Merkel cell carcinoma of the small cell type and small cell carcinoma of the lung

Merkel cell carcinoma (MCC) has a small cell variant, indistinguishable in hematoxylin-eosin sections from metastatic small cell carcinoma of the lung (SCCL). To investigate whether intermediate filament expression is helpful in this distinction, 17 MCCs of the small cell type were examined for cytokeratin, as well as neurofilament protein immunostaining, and compared with 59 intermediate-type MCCs and 22 SCCL. With a pan-cytokeratin cocktail (cytokeratin 1-8, 10, 13-16, 19), most (39 of 55) intermediate-type tumors and, more important, 11 of 16 cases of the small cell variant exhibited focal paranuclear staining with dot-like positivity, crescentic positivity, or both. A combined focal (dot-like/crescentic) and diffuse cytoplasmic pan-cytokeratin staining was seen in additional 8 of 55 intermediate and 4 of 16 small cell MCCs. Cytokeratin 20 also evoked focal cytoplasmic staining and occasionally focal and diffuse positivity in the MCCs, irrespective of the subtype. Exclusively diffuse cytokeratin 20 patterns did not occur. Conversely, most SCCL showed a diffuse expression of pancytokeratin, and all cases remained cytokeratin 20 negative. When neurofilament protein was applied, approximately half of the MCCs (25 of 40), including 7 of 11 of the small cell variant, were positive, whereas all SCCL were negative. In conclusion, the cytokeratin and neurofilament protein patterns of small cell MCCs are identical to the pattern of intermediate MCCs but differ from the profile of SCCL, which may help in the differential diagnosis.

Fine-needle aspiration of Merkel cell carcinoma of the skin with cytomorphology and immunocytochemical correlation

Merkel cell carcinoma (MCC) of the skin is a rare, primary malignant skin neoplasm which can present as a cutaneous nodule. These neoplasms are seen primarily in the elderly and located in the head and neck area or extremities. Twenty-nine aspirates from primary and metastatic lesions obtained by percutaneous fine-needle aspiration in 19 patients have been studied. The cytomorphologic features, clinical information, and immunocytochemical (ICC) findings are detailed. Aspirate smears demonstrated small-to-intermediate-sized cells with a loosely cohesive pattern. Nuclei were round with finely granular chromatin and multiple, small nucleoli. Cells possessed a thin rim of cytoplasm, and infrequent pseudorosette formations were noted in cell groups. ICC results were universally positive for cytokeratin, which showed a paranuclear "dot-like" pattern. Neuron-specific enolase, epithelial membrane antigen, and S-100 protein were positive in varying degrees. Leukocyte common antigen was universally negative. The diagnosis of MCC of the skin by FNA can be made by applying cytologic features in addition to ancillary studies and clinical information.

Merkel cell carcinoma: analysis of clinical, histologic, and immunohistologic features of 132 cases with relation to survival

BACKGROUND

Merkel cell carcinoma (MCC) is an uncommon malignancy of the skin and has a high rate of recurrence and metastasis. There have been few large studies of the biologic behavior of MCC.

OBJECTIVE

Our purpose was to determine whether there were clinical or histologic features of MCC that predict its biologic behavior.

METHODS

We reviewed 132 cases of MCC. Clinical and histologic features were correlated with follow-up information to determine whether any of these were associated with prognosis.

RESULTS

Clinical information was available on 126 patients; 57 were alive, 1 was alive with tumor, 28 died of tumor, 27 died from other causes, and 14 were lost to follow-up. MCC on the buttock/thigh area or trunk had the worst prognosis, and those on the distal extremities had the best prognosis; however, the difference was not statistically significant. Sex and age were not significant factors. Small cell size, high mitotic rate, and large tumor size were associated with a low survival rate. When cell size was excluded, male sex and depth of invasion were associated with a worse survival, although these were not statistically significant.

CONCLUSION

Cell size, mitotic rate, and tumor size are significant factors in relation to the biologic behavior of MCC.

Combined neuroendocrine carcinoma of the skin (Merkel cell tumor) and trichilemmal cyst

We report a case of neuroendocrine (Merkel cell) carcinoma (NC) of the skin, associated with a trichilemmal cyst, showing pagetoid spread into the trichilemmal epithelium. The association of the two lesions may strengthen the hypothesis that NC originates from pluripotent stem cells of adnexal epithelium.

Vla and alpha 6 beta 4 integrin expression in neuroendocrine carcinomas of the skin (their xenografts on nude mice and a corresponding primary culture)

Immunohistological expression of VLA1-5 and alpha 6 beta 4 integrins have been studied in 21 cases of primary neuroendocrine carcinomas of the skin (NECS), three xenografts on nude mice and one NECS cell culture. The phenotypic properties of NECS cells were largely maintained in NECS grafted on athymic nude-mice and in the corresponding cell line. Our results indicate that alpha 1 beta 1 and to a lesser extent alpha 3 beta 1, alpha 5 beta 1 are the main integrins expressed in NECS. In addition, VLA2, 4 and alpha 6 beta 4 are heterogeneously expressed in the same group of tumors and very sparsely present. These data suggest that like neuroblastoma and primitive peripheral neuroectodermal tumor (pPNET) the absence or the heterogeneous distribution of such integrins is correlated with the aggressive behaviour of NECS although long-term follow-up was not available for our cases. On the other hand, the alpha 1 expression could be regarded as a novel marker for differential diagnosis between NECS (alpha 1+) and pPNET (alpha 1-). The alpha 1 beta 1, alpha 2 beta 1, alpha 3 beta 1, alpha 5 beta 1 heterodimers in the 21 NECS studied showed an uniform pericellular staining of both the peripheral cells and central cells of the tumor islands. The predominant expression of alpha 1 beta 1 is consistent with the hypothesis of a primitive epithelial totipotential origin in NECS.

Neurochemical markers in human cutaneous Merkel cells. An immunohistochemical investigation

Merkel cells (MCs) are specialized sensory cells widely distributed in the epithelia of vertebrates. A variable immunohistochemical pattern of neuronal and neurotransmitter markers has been demonstrated in MCs of several species including man. In the present study, we investigated the expression of neurochemical markers in a selected population of human cutaneous MCs by immunofluorescence. The structural neural proteins protein gene product 9.5 and neuron-specific enolase were found to be the most reliable markers for MC identification. Moreover, neurofilament immunoreactivity was shown in a small subset of epidermal MCs. Among the neurotransmitter markers, evidence for expression of calcitonin gene-related peptide, vasoactive intestinal polypeptide, peptide histidine isoleucine amide, neuropeptide Y, neurokinin A, galanin, substance P, somatostatin and phenylethanolamine N-methyltransferase was found. These immunoreactivities were highly variable as far as number of positive cells and staining intensity were concerned. The results indicate that a complex and heterogeneous immunophenotype can be expressed even within a homogeneous population of human MCs.

Merkel cell carcinoma. Diagnosis and treatment

BACKGROUND

Merkel cell carcinoma is an uncommon malignancy of the skin that often portends a poor prognosis. Since its first description by Toker in 1972, a plethora of case reports and articles regarding the etiopathogenesis and treatment have been published spanning multiple medical and surgical disciplines. Much confusion still exists regarding the diagnosis and treatment of this ominous tumor.

OBJECT

Through extensive review of the medical, surgical, and pathological literature, to collate the observations of multiple investigators and summarize these findings.

METHODS

Articles from journals of multiple subspecialties were carefully reviewed with particular emphasis placed on epidemiology, prognosis, histology, immunohistochemistry, electron microscopy, tumor origin, treatment, and work-up of Merkel cell carcinoma.

RESULTS

Merkel cell carcinoma is an aggressive malignant neoplasm. Local recurrence develops in 26-44% of patients despite therapy. Up to three-fourths of patients eventually develop regional nodal metastases with distant metastases occurring in one-third of all patients. Reported overall 5-year survival rates range from 30% to 64%.

CONCLUSION

Treatment recommendations unfortunately are based more on anecdotal than scientific data because of the rarity of the tumor and its recognized high risk. Most authors recommend wide local excision of the primary lesion and regional lymph node resection if lymph nodes are palpable followed by x-irradiation of both the postsurgical bed and lymph node basin. The role of elective lymph node resection in the absence of clinically positive nodes remains controversial.

Immunohistochemical and flow cytometric study of neuroendocrine carcinoma of the skin

Immunohistochemical and flow cytometric analysis using formalin-fixed, paraffin-embedded sections was performed on 10 neuroendocrine carcinomas of the skin (NCS). Grimelius staining was positive in seven tumors. All tumors showed coexpression of CAM 5.2 and neuron-specific enolase with paranuclear dot-like or diffuse cytoplasmic reactivity. Neurofilament was positive in five cases, chromogranin in six, calcitonin and carcinoembryonic antigen in two each, and somatostatin and S-100 protein in one each. Eight primary lesions were diploid and the remaining two were aneuploid; however, two diploid NCS presented as aneuploid metastatic tumors. The follow-up periods ranged from 3 to 66 months (mean 13.6). Six patients died of metastatic diseases between 3 and 33 months (mean 9.2) after the diagnosis. There were no significant correlations among histologic features, DNA ploidy, S-phase fraction, and clinical outcome of the patients with NCS. These results indicate that a panel of antibodies may be required for immunohistochemical confirmation of neuroendocrine differentiation and that a flow cytometric analysis is not a good tool to predict the biologic behavior of NCS.

Expression of alpha subunit of guanine nucleotide-binding protein Go in Merkel cell carcinoma

The alpha subunit of guanine nucleotide-binding protein Go (Go alpha), which was initially isolated from bovine brain, interacts with muscarinic cholinergic receptors and regulates neuronal calcium channels. Go alpha is known to be localized in neural tissues, some endocrine cells, and neuroendocrine tumors. We have immunohistochemically investigated the expression of Go alpha in 4 cases of Merkel cell carcinoma using the method of microwave treatment. In all cases of Merkel cell carcinoma, Go alpha was consistently detected on the plasma membrane and cytoplasm of the tumor cells. Nerve fibers in the skin were also positive for Go alpha, but other epidermal or dermal components such as keratinocytes, melanocytes, fibroblasts, or lymphoid cells were negative. Tumor cells of squamous cell carcinoma, cutaneous lymphoma, sweat gland carcinoma, and malignant melanoma were negative for Go alpha. The present study indicates that Go alpha may be a useful immunohistochemical marker of Merkel cell carcinoma.

The importance of postoperative radiation therapy in the treatment of Merkel cell carcinoma

PURPOSE

To determine the role of postoperative radiation therapy in the treatment of Merkel cell carcinoma (MCC).

METHODS AND MATERIALS

Eighty patients with MCC of the skin were treated with curative intent at the Queensland Radium Institute between 1981 and 1991. Fifty-one patients (63.7%) were referred after initial biopsy for further treatment and 29 patients (36.3%) were referred with locally recurrent disease following primary surgery elsewhere. Thirteen patients (16.3%) presented with nodal disease without a clinically definable primary skin lesion.

RESULTS

Of the 80 patients, 38 had undergone surgery (S) alone, 34 surgery plus radiotherapy (S + RT), 7 RT after incomplete S, and 1 patient had chemotherapy (CT) plus RT. Overall survival at 36 months for all patients was 68%. All of the 38 patients treated with S alone relapsed. The median time to recurrence was 5.5 months. Ten of the 34 patients treated with S + RT relapsed. The median time to recurrence was 16.5 months. Of the 80 patients, 55 have relapsed after primary treatment, 25 have developed systemic metastases, and 26 patients have died as a direct result of MCC.

CONCLUSION

Our large series confirms earlier reports from this Institute and highlights the importance of S + RT over S alone in preventing local recurrence of this highly malignant skin cancer.

Merkel cell carcinoma

Merkel cell carcinoma is a malignant neuroendocrine tumor with features of epithelial differentiation. Biologically aggressive, it may be difficult to diagnose and, particularly in its late stages, even more difficult to treat effectively. This article addresses what is known and what is still controversial about the histogenesis, diagnosis, and management of Merkel cell carcinoma and the structure and function of the Merkel cell from which it is believed to be derived. The incidence, clinical presentation and diagnosis, ultrastructure, immunocytochemistry, treatment, and prognosis of this tumor will be discussed.

A combined occurrence of neuroendocrine carcinoma of the skin and a benign appendageal neoplasm

A 76-year-old Japanese male presented with a subcutaneous nodule in the dorsal cubital region of the right arm. The center of the nodule showed typical features of neuroendocrine carcinoma of the skin. The peripheral portion showed epithelial islands of squamoid cells with horn cysts suggestive of benign appendageal tumor with pilar differentiation. The coexistence of two skin neoplasms in the same lesion would suggest that both tumors developed from common pluripotential stem cell.

Merkel cell carcinoma of the labial mucosa. An immunohistochemical and ultrastructural study with a review of the literature on oral Merkel cell carcinomas

Merkel cell carcinoma is a rare cutaneous neuroendocrine tumor that occurs predominantly in the head and neck region of older patients. An 88-year-old white man had an erythematous, umbilicated tumor on his lower lip, which on histopathologic examination showed solid sheets of infiltrating basaloid round cells with a high mitotic index. Globular, paranuclear immunostaining for low-molecular-weight cytokeratins (Nos. 8, 18, and 19) and neurofilament was observed. On ultrastructural examination, the tumor cells demonstrated paranuclear whorls of intermediate filament aggregates and occasional electron-dense granules. This unique cytokeratin- and neurofilament-staining pattern with coexpression enabled the Merkel cell carcinoma to be differentiated from other small cell malignant tumors that included metastatic neuroendocrine carcinomas from other regions. The follow-up 1 year after surgery and radiation showed that the patient remained disease free. Review of the literature revealed 11 cases of oral Merkel cell carcinomas with a predilection for the labial mucosa of older men. The mode of treatment and the clinical course of these cases are also presented, with an update on therapeutic management of Merkel cell carcinomas.

Non-innervated Merkel cells and Merkel-neurite complexes in human oral mucosa revealed using antiserum to protein gene product 9.5

Merkel cells are non-keratinized cells present in many different epithelia, but whose origin and functional role are still controversial. They were here investigated by means of antisera to the neural and neuroendocrine markers protein gene product 9.5 (PGP 9.5), and neurone-specific enolase. The expression of both markers in Merkel cells of human gingival and palatal mucosa was confirmed. Merkel cell-neurite complexes and isolated non-innervated Merkel cells had a similar morphology when stained by either antiserum. Merkel-neurite complexes were clustered in relatively large numbers in the lingual gingiva, thus constituting structures closely similar to the 'touch domes' in the skin. Clusters of non-innervated cells showing the same immunohistochemical features as Merkel cells were also demonstrated. In other areas of the oral mucosa, the innervated and non-innervated elements were only occasionally seen but there were many encapsulated Meissner-like receptors. When comparing the two different antisera, anti-PGP 9.5 appeared to provide a more consistent labelling of small fibres inside the epithelium and of bulb-like terminals on Merkel cells.

Filamentous inclusions of unusual composition and architecture in a metastatic tumor showing myoepithelial differentiation

A hyaline/eosinophilic cytoplasmic inclusion is described in a metastatic tumor occurring in the omentum and bowel of a 32-year-old white woman. The tumor was essentially of round cell type; was positive for cytokeratin, actin, and S-100 protein by immunohistochemistry; and showed desmosomes (maculae adherentes), tonofibrils, modestly developed myofilaments with focal densities, and a basal lamina by electron microscopy. It was therefore interpreted as showing myoepithelial differentiation. Nearly all cells possessed a large, rounded cytoplasmic inclusion that was architecturally unusual, consisting of intermediate filaments intermingled with lattices of fine filaments. The inclusions exhibited an additionally unusual immunohistochemical staining for both cytokeratin and actin. A comparison with cases described in the literature is made.

Primary neuroendocrine carcinoma of the skin. Clinicopathologic study of 18 cases

The clinical and pathologic features of primary neuroendocrine carcinoma of the skin in 18 elderly patients are reported. The carcinomas arose in the dermis and subcutaneous tissues, particularly on the head and the upper extremities. One tumor occurred in an irradiated area. Using Gould's clinicopathologic classification, we have found four trabecular types, eleven intermediate cell types, and two small cell types. One tumor could not be classified. Other noteworthy pathologic features were association with invasive squamous cell carcinoma, lentiginous melanocytic hyperplasia, and presence of intratumoral melanocytes. Immunoreactivity for cytokeratins (56 kD), neurofilaments, neuron-specific enolase, and epithelial membrane antigen was observed. The paranuclear globular staining pattern of cytokeratins and neurofilaments was conspicuous. The ultrastructural features revealed paranuclear intermediate filament aggregates (fibrous bodies), neurosecretory granules, and cell junctions. In two metastatic tumors, high levels of catecholamines were found. The trabecular types were characterized by localized disease and a good prognosis. The patients with the small cell types died of distant metastases. Postoperative radiotherapy seemed to reduce the rate of local recurrences.

The Merkel cell and associated neoplasms in the eyelids and periocular region

Merkel cells are clear oval cells in the epidermis and outer root sheaths of hair follicles, which are probably of epithelial origin, share ultrastructural features with neuroendocrine cells, and are found in association with touch receptors. In the eyelid, they occur singly in the epidermis and external root sheaths of hairs and eyelashes, and in specialized touch spots alternating with eyelashes. Their typical electron microscopical and antigenic features include dense-core granules, intranuclear rodlets, spinous processes, and a positive reaction for specific cytokeratins, epithelial membrane antigen, neuron-specific enolase, chromogranin and synaptophysin. Merkel cell carcinoma probably develops from precursor cells which give rise to keratinocytes and Merkel cells, and nearly one out of ten Merkel cell carcinomas occur in the eyelid and periocular region. They tend to be bulging lesions near the lid margin of elderly patients, reddish in color, and erythematous with telangiectatic vessels. The diagnosis is based on the frequent presence of neurofilaments and paranuclear aggregates of intermediate filaments in addition to features typical of normal Merkel cells. The tumor often mimics lymphoma or undifferentiated carcinoma and frequently invades lymphatic vessels. One third of Merkel cell carcinomas recur, almost two thirds give rise to regional node metastases, and up to one half metastasize widely and result in death. Initial treatment should be prompt and aggressive, with wide resection and routine postoperative irradiation. Although metastatic lesions often respond to radiation therapy and cytostatic drugs, these treatments are mainly of palliative value.

Neuroendocrine (Merkel-cell) carcinoma of the skin: immunocytochemical and cytomorphologic analysis on fine-needle aspirates

Cytomorphologic and immunocytochemical characteristics of tumor cells from fine-needle aspirates of four neuroendocrine (Merkel-cell) carcinomas of the skin are described. All aspirates were cellular with dispersed small to medium sized tumor cells with scanty cytoplasm. Many mitoses were observed. Careful scrutiny revealed a tendency of the tumor cells to form microacinar and pseudorosette formations as well as small clusters of molding cells. Immunocytochemical analysis of cytospin preparations showed a peculiar dot-like cytokeratin positivity, while neuron-specific enolase staining was more diffuse. A weak S-100 positivity was observed. This staining pattern is highly suggestive of Merkel-cell tumor. It can thus be concluded that immunocytochemical analysis in conjunction with cytomorphology on fine-needle aspirates will allow the identification of neuroendocrine carcinoma of the skin and its differentiation from other small-cell neoplasias of the skin.

Neuroendocrine carcinoma of the lip (Merkel cell tumour) examined by electron microscopy and immunohistochemistry

A definite diagnosis of neuroendocrine carcinoma of the skin is seldom made on initial histological examination; the tumour is usually reported as a poorly differentiated or anaplastic carcinoma. By applying electron microscopy and immunohistochemistry, a correct diagnosis can be made. The ultrastructural examination shows dense-core membrane-bound granules, intermediate perinuclear filaments and desmosome-like junctions. Immunohistochemistry reveals positive staining for neuron-specific enolase and keratin, the latter in a characteristic paranuclear distribution. Confronted with an unusual clinical picture or indefinite histological diagnosis, tissue specimens should be secured for the above mentioned ancillary procedures.

Neuroendocrine carcinoma (Merkel cell tumor?) presenting as a subcutaneous tumor. An ultrastructural and immunohistochemical study of three cases

The clinical and pathological features of three unusual soft tissue tumors are presented. They occurred in the groin of elderly patients in the subcutaneous tissue. In Case 1, the inguino-crural tumor coexisted with a second mass in the pelvis. The tumors had a tendency to recur locally and to invade the regional lymph nodes. Metastatic dissemination of the disease resulted in the death of the patient in Case 3. Histologically, the tumors appeared composed of small round cells with scanty cytoplasms, arranged in diffuse, poorly cohesive or solid sheets. In places, a trabecular pattern was noted. Mitotic figures were numerous. Some cells exhibited argyrophil granules. The ultrastructural study revealed compact whorls of intermediate filaments and neurosecretory granules. All three cases displayed a paranuclear dot-like positive reaction with antibodies to cytokeratins and neurofilaments. A diffuse cytoplasmic immunostaining for neuron-specific enolase was present in Cases 1 and 2. Protein S-100, vimentin and leucocyte common antigen could not be demonstrated. All these characteristics, except for the subcutaneous location, are shared with neuroendocrine (Merkel cell) tumors of the skin.

Synaptophysinlike immunoreactivity in the Merkel cells of pig-snout skin

Synaptophysin is a membrane glycoprotein (Mr 38,000) found in small vesicles with clear content. It is present in neurons and in a variety of neuroendocrine cells and neoplasms, including the neuroendocrine carcinoma of the skin (Merkel cell tumor). We report the presence of synaptophysinlike immunoreactivity in normal Merkel cells of the pig-snout epidermis and vibrissae. The immunostaining was primarily localized in the Merkel cell side opposite to the nerve terminal. This fact suggests that in Merkel cells, as well as in other neuroendocrine cells, synaptophysin could occur in small clear vesicles (accumulated in Merkel cells in the side opposite to the neurite) and not in the secretory granules themselves (which are concentrated in the cellular side apposed to the neurite).

Characterization of Merkel cells and mechanosensory axons of the rat by styryl pyridinium dyes

The epidermal Merkel cells and their sensory innervation serve tactile sensation in vertebrates. In this study the fluorescent cationic mitochondrial dye, 4-(4-diethylaminostyryl)-N-methylpyridinium iodide (4-Di-2-ASP), which has recently been used as a vital stain for motor and autonomic nerve terminals, was tested for its ability to stain Merkel cells and sensory fibers in the snout of the rat. Brightly-fluorescent structures resembling Merkel cells as well as nerve fibers and their terminations were evident in whole mounts of the vibrissal follicle. Unilateral denervation of the vibrissal follicles soon after birth resulted in a staining pattern remarkably similar to that obtained after labelling of the Merkel cells selectively with the fluorescent marker quinacrine, but all fiber staining was abolished. Likewise, in the separated epidermis of other skin regions, including the hairy and glabrous skin of the nose, the staining pattern revealed by 4-Di-2-ASP was indistinguishable from that obtained by quinacrine fluorescence. These results indicate that certain styryl pyridinium dyes may be used as vital stains for epidermal Merkel cells as well as cutaneous mechanosensory axons.

Short communication: deletion 7q, trisomy 6 and 11 in a case of Merkel-cell carcinoma

Chromosome analysis of a metastatic Merkel-cell carcinoma established as xenografted tumor line in nude mice was performed. The analyzed karyotypes showed a stable cytogenetic feature characterized by trisomy 6 and 11 and a partial deletion of the long arm of chromosome #7 with the breakpoint localized at q31.2.

[Clinical aspects and therapy of Merkel cell tumor--report of 4 personal cases and review of the literature]

Four cases of Merkel cell tumor located in the face or on the trunk are presented. In a literature review 339 cases were found and analysed. The Merkel cell tumor is a neuroendocrine tumor of the skin derived from the Merkel cells. It is located most often in the face and neck area. Typically, it is an exophytic node, has a red-blue color and measures 25 mm in diameter on the average. Since it is metastasizing it is a malignant tumor. Regional node metastases were found in 27%, local recurrences occur in 51%, and distant metastases were seen in 32% of the cases. The best therapy is excision with wide margins as is the rule for a malignant skin tumor. While the tumor reacts to radiotherapy, chemotherapy seems to be of no help.

Neuroendocrine (Merkel cell) carcinoma of the skin. Its natural history, diagnosis, and treatment

Over 400 cases of neuroendocrine (Merkel cell) carcinoma of the skin (NCS) have been reported. This tumor continues to pose problems in diagnosis and effective treatment for physicians unfamiliar with its biological characteristics. Reported here are five additional cases of NCS and the literature for this rare neoplasm is comprehensively reviewed. An early and accurate diagnosis is made possible by combining clinical presentation with results of histologic study, immunoperoxidase staining for neuron-specific enolase (NSE), epithelial membrane antigen (EMA), cytokeratins, and electron microscopy. NCS is an aggressive tumor. Depending on the length of follow-up, up to 40% of tumors locally recur, 55% develop regional nodal metastases, and 36% undergo distant metastasis. Survival is sex, but not age, dependent, with an overall 2-year survival rate of 72% (males 58% vs. females 79%). No standard procedure for initial and/or follow-up treatment for NCS exists. The authors recommend that NCS be treated, whenever possible, using the same rationale as applied for the treatment of squamous cell carcinoma of the skin.

Epidermotropic primary neuroendocrine (Merkel cell) carcinoma of the skin with Pautrier-like microabscesses. Report of three cases and review of the literature

Three cases of primary cutaneous neuroendocrine carcinoma involving the face are reported. In the first patient the tumor developed in the scar of a previously excised basal cell carcinoma of the nose, recurred locally, and metastasized to a regional lymph node 2 1/2 years after initial treatment. In the second and third patients the tumors were located on the forehead and were removed with a wide excision. In the second patient the tumor metastasized to regional lymph nodes 1 month after treatment. Light microscopic examination in all patients showed an undifferentiated, small cell, dermal tumor with prominent epidermotropism, forming Pautrier-like microabscesses. Immunohistochemical staining for neuron-specific enolase was positive, and ultrastructural examination revealed numerous cytoplasmic neurosecretory granules and paranuclear aggregates of intermediate-sized filaments. The literature concerning epidermal involvement by primary neuroendocrine carcinoma of the skin is reviewed; the relation with basal cell carcinoma and treatment are discussed.

Cytokeratin and laminin immunostaining in the diagnosis of cutaneous neuro-endocrine (Merkel cell) tumours

Nine cutaneous neuro-endocrine tumours have been immunostained with monoclonal antibodies to low molecular weight cytokeratin (CAM 5.2) and neurofilament. Polyclonal antisera to neurone-specific enolase, calcitonin and laminin were also used. All nine cases showed paranuclear, dot-like positive staining with CAM 5.2 and diffuse cytoplasmic staining for neurone-specific enolase. Neurofilament and calcitonin immunoreactivity could not be demonstrated. All tumours were negative for laminin immunoreactivity. The limitations of staining for neurone-specific enolase are discussed and the value of CAM 5.2 in the differential diagnosis of cutaneous neuro-endocrine tumours is emphasized. The histogenetic implications of the absence of laminin staining are considered.