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Background: There is limited data knowledge of Merkel cell carcinoma (MCC) in Turkey aside from a few case reports. Objective: The aim of this study was to describe the clinical characteristics, demographic features, therapeutic parameters, and outcome of primary cutaneous MCC cases from Turkey. Methods: Digital medical records of the 13 MCC patients who were followed-up at a tertiary referral center were retrospectively analyzed. Clinic, demographic, tumor characteristics, and survival of the patients were retrieved. Results: Most of our patients were elderly. Female predominance was noticed. The most common primary site of the tumors was the lower extremities. The overall survival was 42 months, 68% at first year, 68% at third years, and 29% at fifth years. Conclusion: This is the first largest report from Turkish population with female predominance, and lower extremity tendency. (Ann Dermatol 31(3) 272∼278, 2019)

Merkel cell carcinoma (MCC) is a highly malignant skin cancer characterized by early metastases and poor survival. Although MCC is a rare malignancy, its incidence is rapidly increasing in the U.S. and Europe. The discovery of the Merkel cell polyomavirus (MCPyV) has enormously impacted our understanding of its etiopathogenesis and biology. MCCs are characterized by trilinear differentiation, comprising the expression of neuroendocrine, epithelial and B-lymphoid lineage markers. To date, it is generally accepted that the initial assumption of MCC originating from Merkel cells (MCs) is unlikely. This is owed to their post-mitotic character, absence of MCPyV in MCs and discrepant protein expression pattern in comparison to MCC. Evidence from mouse models suggests that epidermal/dermal stem cells might be of cellular origin in MCC. The recently formulated hypothesis of MCC originating from early B-cells is based on morphology, the consistent expression of early B-cell lineage markers and the finding of clonal immunoglobulin chain rearrangement in MCC cells. In this review we elaborate on the cellular ancestry of MCC, the identification of which could pave the way for novel and more effective therapeutic regimens. (C) 2017 The Authors. Published by Elsevier Ireland Ltd.

Critical reviews in oncology, hematology 116, 99 - 105(2017). doi:10.1016/j.critrevonc.2017.05.009, Published by Elsevier Science, Amsterdam [u.a.]

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 preaEuro/pro-B cells. Here we review putative cells of MCC, including Merkel cells, (epiaEuro)dermal stem cells, and proaEuro/pre-B cells. In the present work, the focus is on the concept of preaEuro/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.

Der Hautarzt 68(3), 204 - 210(2017). doi:10.1007/s00105-017-3945-0, Published by Springer, Berlin

Background: There are few studies focusing on the clinical characteristics of Merkel cell carcinoma (MCC). Objective: To retrospectively analyze the clinical features of our patients and their relationship with sun exposure. Methods: Thirty-six patients diagnosed with MCC (20 men and 16 women, mean age 72.08 years) were included in the study. Results: 21 patients developed MCC in sun-exposed skin and 15 patients in non-sun-exposed areas. MCC was >2 cm in 19 cases. Six of the 7 patients who died as a result of MCC had non-sun-exposed tumors. Only tumor size >2 cm significantly influenced survival (p = 0.033). Conclusion: Sun-exposed lesions tended to be

Trabecular carcinoma is a rare cutaneous neuroendocrine carcinoma that probably originates from the Merkel cells that are usually found in the basal layer of the epidermis. The treatment of Merkel cell carcinoma is controversial and there is no specific therapeutic protocol because of the small number of cases that have been published. The procedures used to treat Merkel cell carcinoma must be tailored to minimise morbidity while maximising survival. Because the condition is so rare and difficult to diagnose and treat, we report three cases of orbitopalpebral tumours that confirm the local and regional aggressiveness and the high metastatic potential of this tumour.

Merkel cell carcinoma is an unusual, aggressive skin tumour, with a tendency to recur after its surgical extirpation. Five cases of tumours in the cervicofacial region seen at our Centre in the last 5 years are presented, along with a review of the literature, focusing on its etiopathogeneis, approach and treatment. © 2010 Elsevier EspaS.L. All rights reserved.

Merkel cell carcinoma (MCC), also known as primary neuroendocrine or trabecular carcinoma of the skin, is an aggressive primary cutaneous carcinoma first described by Toker in 1972 [21]. MCC cells share ultrastructural and immunohistochemical neuroendocrine features with epidermal Merkel cells, but their precise histogenetic origin remains uncertain.

We describe one case of Merkel cell tumor (MCT) of the eyelid diagnosed by fine-needle aspiration (FNA). The main cytologic features were: isolated cells, loose cohesive sheets, and rosette-like structures in a hematic background. The cells were round to ovoid and very uniform. Chromatin was finely granular and frequent mitotic figures were observed. Under close scrutiny small faintly stained juxtanuclear “caps” were seen. A strong dot-like positivity for CK22 and NFP was observed in the position corresponding to the “caps.” NSE positivity was diffuse, although a weak dot-like positivity was seen in some cells. S-100 was negative. Both the cytologic features and the immunocytologic profile of Merkel cell turmor are very characteristic. FNA enables an early and confident diagnosis of this aggressive tumor and an early planning of surgery. © 1994 Wiley-Liss, Inc.

Merkel cell tumour is a recently described aggressive primary neoplasm of the skin. It is commonly seen in the elderly, on the head and neck or extremities. Surgical excision is the recommended treatment, but local recurrence or dissemination is not an uncommon consequence of this form of therapy. Radiotherapy is usually used as a palliative treatment for metastatic disease. We present two patients, in one an extensive primary was controlled by superficial X-ray, in the other, lymph node metastases were controlled with radiotherapy after excision of the primary.

The Merkel-cell tumor (trabecular carcinoma) is an unusual skin appendage malignancy that often recurs locally after initial excision. Occasional regional node metastasis occurs with the larger lesions. This report details our experience with six patients who developed this lesion. Illustrated is a spectrum of malignancy from a locally limited tumor to ones that led to death of the patients. Recognition of this rare tumor is important to ensure proper local treatment with close follow-up observation of the patient.

Es wird uber vier Falle eines Merkelzelltumors mit unterschiedlichem klinischen Verlauf und Lokalisation im Gesicht und am Stamm berichtet. Bezuglich der Klinik wurden 339 Falle eines Merkelzelltumors aus der Literatur ausgewertet. Beim Merkelzelltumor handelt es sich um einen von den Merkelschen Zellen ausgehenden neuroendokrinen Hauttumor. Er findet sich zu 47% im Kopf-Halsbereich, hat eine durchschnittliche Grose von 25 mm, liegt typischerweise uber dem Hautniveau und zeichnet sich klinisch durch seine rotlich-livide Farbe aus. Aufgrund der Metastasierung und des infiltrativen Wachstums ist er als maligne einzuordnen. In 27% bestehen Lymphknotenmetastasen, in 51 % kommt es zu Lokalrezidiven und in 32% treten Fernmetastasen auf. Die Therapie der Wahl besteht in einer fruhzeitigen Excision mit einem Sicherheitsabstand, wie er bei malignen Hauttumoren ublich ist. Eine Strahlensensibilitat liegt vor; ob auch eine chemotherapeutische Beeinflusbarkeit besteht, ist jedoch nicht sicher.

Merkel-cell tumor was first described by Toker in 1972, as 'trabecular carcinoma', then a couple of years later, it was considered as involving the Merkel cell because of its characteristic neurosecretory granulations and intermediate filaments. Based on four cases, three involving the lids, one the orbital rim, the authors briefly summarize the current thoughts concerning the Merkel cell tumor, its clinical features, histological appearance and diagnosis, its prognosis and therapeutic management.

We report the electron microscopic studies of three trabecular carcinomas of the skin. The presence of neurosecretory granules in all three tumors suggests that trabecular carcinoma originates from one of the neurocrest derivatives, most probably, Merkel cells. The ultrastructural findings confirm Toker's original concept that trabecular carcinomas comprise a distinct group of skin tumor. The recognition of these tumors would enable one to make such a diagnosis on frozen section, which, in turn, might provide an opportunity for more specific cytochemical and immunofluorescent characterization.

Five patients had trabecular carcinomas of the skin. The growths originate within the dermis or in the immediate subcutis, and display a uniform morphology. They are composed of solid trabeculae that lack definite acini. A derivation from cells that are capable of reproducing primitive sudoriferous structures is postulated. The lesions have been encountered in elderly patients of both sexes, and the larger tumors have disseminated actively by lymphatic pathways. Trabecular carcinomas may occasion diagnostic difficulty, for they may be misinterpreted as cutaneous metastases from visceral cancers. The histological features of these tumors are not sufficiently distinctive to permit differentiation from anaplastic metastatic carcinomas. Confirmation of their primary dermal origin is dependent upon the clinical outcome. Familiarity with their existence is, however, of importance in the evaluation of cutaneous malignancy.

Four patients with primary neuroendocrine carcinoma of the skin (Merkel cell or trabecular carcinoma) are reported to document their response to radiotheraphy. In three patients there was complete response following radiation treatment, with no local recurrence, whilst the other patient died later with distant metastases. In one patient, post-operative irradiation after excision of an involved local node prevented the growth of further tumour in this nodal group but the unirradiated primary site recurred after initial wide local excision only. This rare tumour appears to be radioresponsive, and although more clinical data are required, we would advocate a wider study of radiotherapy to the primary lesion after biopsy or excision biopsy, in association with prophylactic nodal irradiation. These tumours occur predominantly in elderly people in whom the avoidance of extensive surgery is particularly desirable.

A case of trabecular carcinoma of the skin in a 62 year old Caucasian male is reported. The lesions occurred on the face, ear, chest, abdominal wall, and the upper extremity over a period of four years. At the light microscopic level the lesions were confused with metastatic carcinoma, lymphoma, and adult neuroblastoma. Ultrastructural study revealed the presence of not only neurosecretory granules but also premelanosomes in the tumor cells.

While performing an electron microscopic examination of the skin for diagnostic purposes, we observed a cluster of cells with dense-core membrane-bound granules in the external root sheath of a hair follicle. The finding of Merkel cells in hair follicle could help to explain some histogenetic features of neuroendocrine tumors of the skin.

A case of trabecular carcinoma of the skin that resulted in prequarter amputation of the arm for local tumor aggressiveness is presented. The tumor was originally diagnosed as metastatic, most probably neuroblastoma, leading to inadequate local resection that resulted in recurrence with extensive regional nodal metastases. The importance of recognizing trabecular carcinoma as a primary tumor of the skin with a potential for recurrence and metastasis is underscored, primarily since initial total excision with adequate margins of resection has proven in most instances to be curative.

Serum α-fetoprotein (af) of rats during hepatocarcinogenesis by 3′-methyl-4-(dimethylamino)azobenzene (3′-Me-DAB) or N-2-Fluorenylacetamide (FAA) was checked by the micro-Ouchterlony method throughout the course of the study. The serum af appeared in two phases, early from the 3rd to 5th week and late during the development of large carcinomas. The frequency of early appearance of serum af varied considerably according to the difference in age, sex, and strain of the animals or the difference in type or dose of the carcinogen. In general, 3′-Me-DAB was a much stronger carcinogen than FAA in producing early serum af. A good correlation was observed between the serum af level and the intensity of oval cell proliferation in the liver at this stage. The cell composing the nodular hyperplasia in 3′-Me-DAB or the area of hyperplasia in FAA carcinogenesis, which replaced the major part of the liver in the next stage and had been considered the most possible forerunner of the carcinoma, did not seem to produce af. The serum af in the late phase was produced by the carcinoma. The majority of the 3′-Me-DAB-induced carcinomas belonged to the mixed type carcinoma. This type of carcinoma was strongly af-producing with the required minimal size of 10 mm in diameter for positive serum af. Most of the FAA-induced carcinomas were of the trabecular type. This type of carcinoma was relatively weak in af-production and the serum af was negative until a trabecular carcinoma became larger than 20 mm in diameter. The appearance of early serum af was distinct evidence of a fair progress of hepatocarcinogenesis, and a positive correlation was found between the degree of this phenomenon and the frequency of development of a carcinoma producing large amounts of af. However, the appearance of early serum af was not an absolute requisite for later development of carcinomas. a-Foelig;toproteine et hepatocarcinogenese chez les rats ayant absorbe du 3′-methyl-4-(dimethylamino) azobenzene ou du n-2-fluorenylacetamide L'a-fœoproetine (af) serique des rats a ete etudieee par la methode micro-Ouchterlony tout au long de l'hepatocarcinoginese par le 3′methyl-4- (dimkthylamino) arobenzene (3′-Me-DAB) ou le N-2-fluoreenylacetamide (FAA). L'af serique est apparue en deux stades, soit entre la troiseme et la cinquieme semaine (apparition rapide), soit air stade du developpement d'un gros carcinome (apparition tardive). %%La frequence de l'apparition rapide de l'af serique varie considerablement selon l'ǎge, le sexe et la souche des animaux ou selon le type ou la dose du carcinogene. En general, le 3′-Me-DAB est un carcinogene beaucoup plus puissant que la FAA si l'on considere la production rapide d'af serique. Une correlation nette a ete observee entre le niveau de l'af serique et l'intensite de la proliferation des cellules ovales du foie a ce stade. Les cellules qui composent l'hyperplasie nodulaire dans la carcinogenese par le 3′-Me-DAB, ou la zone hyperplasique dans la carcinogenese par le FAA, qui ont remplace la majeure partie du foie au stade suivant et qui ont ete considerees comme les precurseurs les plus probables du carcinome, ne semblent pas produire d'af. Dans la phase tardive, l'af serique est produite par le carcinome. La majorite des carcinomes induits par le 3′-Me-DAB appartiennent au type mixte. Ce type produit enormement d'af, dont la recherche dans le serum est positive tant que le carcinome n'a pas moins de 10 mm de diametre. La plupart des carcinomes induits par le FAA etaient de type trabeculaire. Ce type produit relativement peu d'af, dont la recherche dans le serum est negative tant que le carcinome n'a pas plus de 20 mm de diametre. L'apparition rapide d'af dans le serum est une preuve nette d'un grand progres de l'hepatocarcinogenese, et une correlation positive a ete constatee entre le degre de ce phenomene et la frequence du developpement d'un carcinome produisant de grandes quantites d'af. Toutefois, l'apparition rapide d'af serique n'est pas un prealable absolu du developpement ulterieur des carcinomes.

Summary Several lines of transplantable hepatomas induced by feeding rats 3′-methyl-4-dimethylaminoazobenzene have been established in this laboratory. The primary tumor cells were placed into an air pouch on the back of recipients that were previously conditioned by intramuscular injections of cortisone. This technic is reproducible. If desired, a new transplantable tumor line can be produced almost at will. The resultant transplantable hepatomas which were derived from the two main types of primary tumors, the adenocarcinoma and the trabecular carcinoma, exhibited different biologic behavior and histologic features. Significant morphologic changes occurred in the tumor cells of the first two passages especially if the tumor was of adenocarcinomatous origin. After a few passages these tumors became less differentiated and more stable.