Merkel cell carcinoma  , also called neuroendocrine  cancer  of the skin, is a rare type of disease in which malignant  (cancer) cells  are found on or just beneath the skin and in hair follicles  . Merkel cell carcinoma usually appears as firm, painless, shiny lumps of skin. These lumps or tumors  can be red, pink, or blue in color and vary in size from less than a quarter of an inch to more than two inches. Merkel cell carcinoma is usually found on the sun-exposed areas of the head, neck, arms, and legs. This type of cancer occurs mostly in whites between 60 and 80 years of age, but it can occur in people of other races and ages as well.

Merkel cell carcinoma grows rapidly and often metastasizes  (spreads) to other parts of the body. Even relatively small tumors are capable of metastasizing. When the disease spreads, it tends to spread to the regional  (nearby) lymph nodes  and may also spread to the liver  , bone, lungs  , and brain. Lymph nodes are small, bean-shaped structures that are found throughout the body. They produce and store infection  -fighting cells.

Treatment of Merkel cell carcinoma depends on the stage  of the disease, and the patient’s age and overall condition.

Stage Explanation

Stages of Merkel cell carcinoma

After Merkel cell carcinoma  has been diagnosed  (found), more tests will be done to find out if cancer  cells  have spread from the place the cancer started to other parts of the body. The process used to find out whether the cancer has spread to other parts of the body is called staging.  It is important to know the stage  of the disease to plan the best treatment. The following stages are used for Merkel cell carcinoma:

Stage I

The primary tumor  has not spread to lymph nodes  or other parts of the body. Lymph nodes are small, bean-shaped structures that are found throughout the body. They produce and store infection  -fighting cells.

Stage II

The cancer  has spread to nearby lymph nodes  , but has not spread to other parts of the body.

Stage III

The cancer  has spread beyond nearby lymph nodes  and to other parts of the body.

Recurrent

Recurrent disease  means that the cancer has recurred  (come back) after it has been treated. It may come back in the same part of the body or in another part of the body.

Treatment Option Overview

How Merkel cell carcinoma is treated

There are treatments for all patients with Merkel cell carcinoma  . Three kinds of treatment are used:

—      Surgery  (taking out the cancer  ).

—      Radiation therapy  (using high-dose  x-rays  or other high-energy rays to kill cancer cells  ).

—      Chemotherapy  (using drugs  to kill cancer cells).

There are several different types of surgery that may be used to remove the tumor.  These include:

—      Wide surgical  excision  takes out the cancer and some of the skin around the tumor.

—      Cryosurgery  freezes the tumor and then removes it.

—      Micrographic surgery  (Mohs surgery) is a tissue  -sparing technique that removes only the tumor.

Radiation therapy uses high-energy x-rays to kill cancer cells and shrink tumors. Radiation  may come from a machine outside the body (external radiation therapy  ) or from putting materials that produce radiation (radioisotopes  ) through thin plastic tubes in the area where the cancer cells are found (internal radiation therapy  ).

Chemotherapy uses drugs to kill cancer cells. Chemotherapy may be taken by pill, or it may be put into the body by a needle in a vein or muscle. Chemotherapy is called a systemic treatment  because the drugs enter the bloodstream, travel through the body, and can kill cancer cells throughout the body.

If a doctor removes all the cancer that can be seen at the time of the operation, a patient may be given chemotherapy after surgery to kill any cancer cells that are left. Chemotherapy given after an operation to a person who has no cancer cells that can be found is called adjuvant chemotherapy  .

Stage I Merkel Cell Carcinoma

Treatment may be one of the following:

—      Surgery  alone.

—      Surgery followed by radiation therapy  to the tumor  site and regional lymph nodes

Stage II Merkel Cell Carcinoma

Treatment may be one of the following:

—      Surgery  alone.

—      Surgery followed by radiation therapy  to the tumor  site and regional lymph nodes  .

—      Surgery with or without radiation therapy followed by adjuvant chemotherapy  .

Stage III Merkel Cell Carcinoma

Treatment will probably be chemotherapy. 

Recurrent Merkel Cell Carcinoma

Treatment may be one of the following:

—      Surgery  alone.

—      Surgery followed by radiation therapy  to the tumor  site and regional lymph nodes

—      Surgery with or without radiation therapy followed by adjuvant chemotherapy

Changes to This Summary (07/20/2005)

The PDQ  cancer  information summaries are reviewed regularly and updated as new information becomes available. This section describes the latest changes made to this summary as of the date above.

Editorial changes were made to this summary, and links to the NCI  Dictionary of Cancer Terms were added.

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D. Pectasides^a, G. Papaxoinis^a, E. Pectasides^a, H. Galani^b, E. Razi^c, N. Katodrytis^e, G. Fountzilas^d, T. Economopoulos^{a a}2nd Department of Internal Medicine, Propaedeutic, Oncology Section, University of Athens, Attikon University Hospital, Haidari, ^b2nd Department of Medical Oncology, Henry Dunan Hospital,^c2nd Department of Medical Oncology, Hygia Hospital, Athens, and ^dDepartment of Medical Oncology, Papageorgiou General Hospital, Aristotle University of Thessaloniki School of Medicine, Thessaloniki, Greece; ^eDepartment of Medical Oncology, Nicosia, Cyprus

Background: The purpose of this retrospective study was to present the epidemiological and clinical characteristics of 24 patients with Merkel cell carcinoma of the skin (MCC) and their response to various therapeutic modalities. Methods: The tumor registry of the Hellenic Cooperative Oncology Group was used to identify patients with MCC diagnosed between 1986 and 2006. Results: The most frequent primary sites were the extremities (50%), followed by the head (33%) and the trunk (17%). Median time of follow-up was 24 months. Sixteen patients were initially diagnosed with stage I, 5 patients with stage II, and 3 patients with stage III (metastatic) disease. Six patients with stage I disease received adjuvant chemotherapy (CT) and/or radiotherapy (RT). All patients with stage I disease treated only with surgery relapsed, whereas 33% of the patients treated with adjuvant therapy recurred. All patients with stage II disease received adjuvant treatment. Among them, 2 patients relapsed. Disease-free survival (DFS) and overall survival (OS) did not differ significantly between patients with stage I and II disease (stage I: 4-year DFS 27%, 4-year OS 56%; stage II: 4-year DFS 60%, 4-year OS 80%). Patients treated with adjuvant therapy had significantly better DFS than those treated only with surgery (p = 0.012), but OS did not differ significantly (adjuvant group: 4-year DFS 59%, 4-year OS 74%; surgery group: 4-year DFS 10%, 4-year OS 50%). Eleven patients with locally advanced or metastatic disease received CT. The response rate was 73% (complete remission 18%), median progression-free survival was 10 months and median OS was 14 months. Complete remission was achieved in 2 other cases, with the addition of RT after CT. Conclusions: MCC is an aggressive neoplasm with significant chemosensitivity and radiosensitivity, but poor outcome. The role of adjuvant treatment should be further investigated.

Copyright © 2008 S. Karger AG, Basel

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Merkel cell carcinoma (MCC) is an aggressive tumor, the incidence of which is seemingly increased in immunocompromised patients. We report on a new case of MCC occurring in a 69-year-old male liver transplant recipient 6.5 years after transplantation. The outcome was marked by early skin and lymph node relapses treated by radiotherapy alone, and the patient ultimately died 30 months after first diagnosis. Together with data from the literature, this case emphasizes the importance of early diagnosis and adequate management of this aggressive disease for which wide initial surgical excision, accurate staging, and close follow-up are of critical importance to outcome, especially in this setting of immunosuppressive treatment, which is usually associated with a higher rate of recurrence.

Keywords: Adenocarcinoma; Liver transplant

Document Type: Research article

Affiliations: 1: 1 Department of Dermatology, University of Montpellier I, Hôpital Saint Eloi, Montpellier, France 2: 2 Department of Internal Medicine, University of Montpellier I, Hôpital Saint Eloi, Montpellier, France

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Merkel cell carcinoma is an uncommon aggressive primary cutaneous neuroendocrine carcinoma. Histologically, the differential diagnosis includes the ’small round cell’ tumor group, particularly metastatic small cell carcinoma and blastic hematological malignancies involving skin/soft tissues. Terminal deoxynucleotidyl transferase (TdT) is a DNA polymerase, which is a sensitive and specific antibody for acute lymphoblastic lymphoma with a small proportion of acute myeloid leukemia showing positivity. This study investigates the expression of TdT in 20 cases with initial diagnosis of Merkel cell carcinoma. Archival blocks and slides were retrieved and reviewed and clinical information obtained from patient charts. Immunohistochemistry was performed and graded as: 0, no staining; 1+, less than 50% staining in the cells; 2+, 50% or more staining in the cells. After review, 15 cases were confirmed as Merkel cell carcinoma. Immunohistochemical positivity was as follows: 8/15 cases were positive for TdT with strong nuclear staining, morphologically resembling ‘blasts’, AE1AE3, CAM5.2 (15/15) (both membrane and paranuclear dot positivity), CD56 and BCL-2 (15/15), Synaptophysin (13/15), Chromogranin A (11/15), NSE (15/15), CK20 (14/15), CK7 (3/15), both CK7 and CK20 (3/15), CD117 (8/15), CD99 (2/15), CD10 (1/15). One case was negative for CK7/CK20. All 15 cases were negative for thyroid transcription factor-1, LCA, CD20, CD3 and CD34. Expanded immunohistochemical panel with positive staining for epithelial/neuroendocrine markers, CK20, negative staining for hematolymphoid markers and awareness of TdT expression and other markers that show overlap with blastic hematological malignancies avoids misinterpretation in the diagnosis of Merkel cell carcinoma. This aids in further diagnosis of Merkel cell carcinoma, avoiding the potential diagnostic pitfall with other small round cell tumo tumors and hematological malignancies primary or metastatic to the skin.

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Abstract:

Pollheimer VS, Bodo K, Pollheimer MJ, Zigeuner R, Langner C. Merkel cell carcinoma metastasizing to the kidney mimicking primary neuroendocrine renal cancer. Case report. APMIS 2207;115:774-7.

A 56-year-old male with a history of cutaneous neuroendocrine (Merkel cell) carcinoma presented with a solid mass of the left kidney, measuring 10 cm in largest diameter. On histology, the tumour was composed of loosely packed uniform cells with round-to-oval nuclei and scant cytoplasm. Immunohistochemically, the tumour cells diffusely expressed pancytokeratin and neuroendocrine markers, such as chromogranin A, synaptophysin and CD56 (NCAM). Distinct paranuclear dot-like expression of cytokeratin 20 showed the lesion to be metastatic Merkel cell carcinoma. This is the first reported case of Merkel cell carcinoma metastatic to the kidney mimicking primary neuroendocrine renal cancer. We discuss the differential diagnosis of the tumour and perform a systematic literature review, including potential indications for renal tumour biopsy in patients with a history of nonrenal malignancy.

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Proceedings of the 1st Symposium of the Japanese Society for Ultrastructural Cutaneous Biology, Tokyo, 24-25 November 1999

Edited by

H. Suzuki, Department of Dermatology, Surugadai Nihon University Hospital, 1-8-13 Kanda- urugadai, Chioyoda-ku, Tokyo 101-8309, Japan T. Ono, Department of Dermatology, Kumamoto University School of Medicine, 1-1-1 Honjyo, Kumamoto 860-8556, Japan

Included in series International Congress, 1187

Description

The ICS series is proud to publish the proceedings of the 1st Symposium of the Japanese Society for Ultrastructural Cutaneous Biology, which will make a significant contribution to advances in the dermatological field.

Dr. Friedrich Merkel first identified the Merkel cells, which he called Tastzellen (touch cells) in 1875. However, it was not until the 1960s that the existence of Merkel cells in the human skin was confirmed by Dr. Cauna using electron microscopy.

1902 saw the discovery of the Haarscheiben (hair discs) by Dr. Felix Pinkus who reported that they are many Merkel cells beneath the epidermis of the disc. Today, the Merkel cell-neurite complex in the hair disc is regarded as a slow-adapting type I mechanoreceptor unit.

Since 1978, when Drs. Tang and Toker reported the concept of Merkel cell carcinoma, many cases have been identified worldwide. Neurobiology, neuropeptides and interaction between cutaneous innervation and the cells are now important topics in the dermatological field.

This volume brings together research on new developments in Merkel cells, Merkel cell carcinoma and neurobiology of the skin. The proceedings comprise the following sections:

—      Morphological aspects of Merkel cells in skin and oral mucosa

—      Physiological aspects of Merkel cells, as mechanoreceptors

—      Merkel cells in hair discs and hair follicles

—      Merkel cell hyperplasia and Merkel cell carcinoma

—      Neurobiology of the skin

It intends to improve understanding of the origin and nature of Merkel cells and related pathophysiological processes in the skin.

Audience

Perfect for dermatologists and neurobiologists of the skin

Contents

Morphological aspects of Merkel cells in skin and oral mucosa. Morphology and distribution of Merkel cells in some vertebrates (K. Toyoshima et al.). Morphological and developmental characteristics of oral mucosal Merkel cells (T. Tachibana, T. Nawa). Developmental origin of Merkel cells in birds (M. Grim, D. Halata). Topography of nerve terminals in Merkel nerve endings in mammals (Z. Halata, K.I. Baumann). Ultrastructure of the Merkel cells and their dependency on the nerve endings (K. Kurosumi). Merkel cell as a paraneuron (T. Fujita, S. Yoshie).

Physiological aspects of Merkel cells as mechanoreceptors. Calcium inflow of single Merkel cell in response to direct mechanical stimulation (M. Tazaki et al.). Calcium influx and calcium induced calcium release in mechanically stimulated Merkel cells of rat sinus hair type I mechanoreceptors (K.I. Baumann et al.). Merkel cells, possible mechanoreceptors (H. Ogawa).

Merkel cells in hair discs and hair follicles. Human haarscheiben: development, distribution and keratinocyte differentation (I. Moll). Postnatal morphogenesis and proliferative activity of epidermis in hair discs (H. Suzuki et al.). Follicular Merkel cells in different body sites of mice, guinea pigs and rats (Y. Narisawa et al.). Characteristics of Merkel cells in hair follicles in the facial skin (S. Uchigasaki et al.).

Merkel cell hyperplasia and Merkel cell carcinoma. Merkel cell hyperplasia in human skin tumors - potential biological significance and clues to diagnosis in dermatopathology (W. Hartschuh, E. Weihe, T. Schulz). Merkel cell carcinoma in Japan (T. Ono, K. Kayashima, K. Maruo). Clinical and histopathological diversity of Merkel cell carcinoma (K-I. Kayashima, T. Ono). Merkel cell carcinoma associated with bowenoid actinic keratosis (T. Muramatsu et al.). Immunohistochemical analysis of neuroendocrine carcinomas (Y. Takeuchi et al.). Ganglioside expression in Merkel cell carcinoma (M. Muto et al.). Merkel cell carcinoma with spontaneous regression (K. Maruo, K. Kayashima, T. Ono). Merkel cell carcinoma: an immunohistochemical and ultrastructural study (M. Kagoura et al.). Immunohistochemical and ultrastructural study of Merkel cell carcinoma of the thigh (T. Ochiai et al.).

Neurobiology of the skin. Keratinocyte nerve growth factor: more than just a neurotrophin (C. Pinceli, A. Marconi). Low-energy helium-neon laser irradiation stimulates basic fibroblast growth factor release from cultured human dermal fibroblasts (Y.-H. Kao, H.-S. Yu). Regulation of epidermal Langerhans cells by calcitonin gene-related peptide (J. Hosoi et al.). The production of the neurotrophic factors by epidermal Langerhans cells (H. Torii, K. Tamaki, R.D. Granstein). The alterations of cutaneous nervous system with cyclosporin A treatment in atopic dermatitis (M. Morohashi, M. Toyoda). New insights into the participation of cutaneous neurologic factors in photoaging processes (M. Toyoda et al.). Differences of skin reactions in adult and neonatal mice induced by substance P (N. Suzuki et al.). Anxiety and delayed adverse reactions to iodinated contrast media used in radiological examinations (Y. Mitsuhashi et al.). Index of authors. Keyword index.

Bibliographic & ordering Information

Hardbound, 400 pages, publication date: JUN-2000

ISBN-13: 978-0-444-50221-6

ISBN-10: 0-444-50221-1

Imprint: EXCERPTA MEDICA

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In the general population Merkel’s cell carcinoma (MCC) is an aggressive neuroendocrine skin cancer. More than 600 cases have been reported. MCC seems to be common in transplant recipients, with 41 cases being reported to the Cincinnati Transplant Tumor Registry, and another 11 in the transplant literature. In the general population, it is a disease of older adults, with only 51% of cases occurring below the age of 50 years. In transplant patients, the mean age at diagnosis was 53 (range 33-78) years, and 29% of recipients were <50 years old. The tumor appeared from 5 to 286 (mean 91.5) months after the transplant. Of 44 lesions that occurred in 41 patients, the distribution was similar to that seen in the general population, with 36% occurring on the head and neck, 32% on the upper extremities, 16% on the trunk, 9% at unknown sites, and 7% on the lower extremities. Twenty of the patients (49%) had 22 other malignancies, the great majority of which (91%) were other skin cancers. Treatment depended on the stage of the disease and included wide surgical excision, radical lymph node dissection, radiation therapy, and chemotherapy. In transplant patients, MCC probably proved to be more aggressive than in the general population in that 68% of patients developed lymph node metastases and 56% died of their malignancies. Furthermore, one third of surviving patients still have active cancers from which they may die. Also, follow-up of survivors has been relatively short, with a mean of only 18 (range 0-135) months.

Related Links

—      Merkel cell carcinoma: report of 10 cases and review of the literature. [J Am Acad Dermatol. 2000]

—      Merkel cell carcinoma and melanoma: etiological similarities and differences. [Cancer Epidemiol Biomarkers Prev. 1999]

—      Merkel cell carcinoma: a clinicopathological study of 11 cases. [J Eur Acad Dermatol Venereol. 2005]

—      Merkel cell carcinoma in a liver transplant patient. [Am J Clin Dermatol. 2007]

—      Second neoplasms in patients with Merkel cell carcinoma. [Cancer. 2001]

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Seventy patients with Merkel cell carcinoma were treated at Memorial Sloan-kettering Cancer Center between 1969 and 1989. The overall estimated 5-year survival rate was 64%. Factors predictive of improved survival included head and neck site and negative lymph nodes at presentation. Local recurrence was seen in 18 patients (26%) and did not correlate with patient-, tumor-, or treatment-related variables. Nine patients with local recurrence (50%) were free of disease following aggressive reoperation. Regional nodes were involved at some point during the course of the disease in forty-six patients (66%). Regional lymph node involvement was apparent within 2 years of diagnosis in 40 (87%) of 46 patients in whom it occurred. Systemic disease was nearly uniformly preceded by the appearance of nodal metastases and was uniformly fatal regardless of subsequent therapy. This suggests an orderly “cascade” pattern of spread for this tumor, in which elective regional lymph node dissection may be justified. Our recommendations for treatment include a wide excision of the primary tumor and either elective or early therapeutic regional node dissection. The role of adjuvant radiotherapy or chemotherapy remains unproven.

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Merkel cell carcinoma is a rare, malignant tumor of the skin characterized by significant incidence of local recurrence (30% to 45%), early involvement of the locoregional lymph nodes (40% to 70%) and distant metastases (30% to 50%) (17).

Due to its aggressiveness and benign clinical appearance, the prognosis of this neoplasm is poor (17). Reported overall 5-year survival rates range from 30% to 64% (11, 28).
Toker published the first complete description of this neoplasm in 1972, originally describing it as “trabecular carcinoma” (25). Nearly 1000 cases are reported in the English-language literature since the initial description (16).

This tumor is also known as cutaneous small cell undifferentiated carcinoma. At the present, the tumour is classified as a neuroendocrine malignancy (APUDoma) of the skin, generally occurring in elderly patients (12, 15).

Macroscopically the primary tumor arises as a small, non-ulcerated, painless, bluish red, intradermal nodular mass often located in sun-exposed areas of the skin (17).

The commonest sites of presentation are the head and the neck and it is slightly more common in females (1, 19). In rare cases (nearly 3%) the Merkel cell carcinoma presented as a metastatic disease of unknown primary, usually in lymph nodes (16).

This cancer arises in the dermis and subcutaneous tissues from Merkel’s cells located in the basal layer of the epidermis and expresses neuroendocrine markers such as neuron-specific enolase, chromogranin, synaptopysin and neurofilament proteins (21).

The most frequent sites of metastasis are distant lymph nodes, distant skin, lung, central nervous system and bone (16).

The histologic diagnosis can be difficult, because with the conventional light microscopy Merkel cell carcinoma can be misdiagnosed as any other poorly differentiated small cell neoplasm (17). The electron microscopy showing a triad of characteristic features (high mitotic index, apoptosis and vescicular nuclei with small nucleoli) and the immunohistochemical staining (neuron-specific enolase and cytokeratin) play an important role in the early diagnosis (3, 9, 22, 26).

The most common staging system is that described by Yiengpruksawan et al., stage I disease for isolated local lesion, stage II disease is characterized by metastatic spread to regional lymph nodes and stage III has evidence of distant metastatic disease at the time of initial presentation (27). Recently a new modified staging system was performed: stage Ia (primary disease only, size < 2cm), stage Ib (primary disease only, size > 2cm), stage II (regional nodal disease), stage III (beyond regional nodes and/or distant disease) (24).

The management of Merkel cell carcinoma is still a challenging problem; the rarity of this tumor and the lack of data concerning its true incidence and long-term responsiveness to therapies make it difficult to determine an “ideal” treatment. Merkel cell carcinoma should be treated aggressively with wide excision of the primary lesion (2-3 cm margins), and prophylactic lymphadenectomy followed by irradiation to the primary site (8, 20). The Mohs micrographic surgery tecnique is resulted to be comparable, or even better, than wide excision for the control of primary skin disease (6, 10, 14).
If lymph nodes involvement is detected, then irradiation to the lymph nodal region must be performed (4).

Chemotherapy is reserved for systemic disease, though the success of this treatment is limited and no chemotherapy protocol has been shown to improve survival (18, 20). Chemotherapeutic regimens most often used for the treatment of Merkel cell carcinoma are similar to those performed for the small cell carcinoma of the lung ( 7, 23, 27).

Radiotherapy alone can be used as palliative treatment with good control of primary and lymph node metastases (5).

The lymph nodal involvement is correlated with the 5-year survival (survival rates for nodal versus no-nodal involvement were 48% and 88% respectively) (27), but it was not associated with overall survival (2, 14). For this reason, some Authors suggest the use of sentinel lymph node biopsy to select those patients who need lymphadenectomy for regional control of disease. (13)

The local recurrence rate is frequentely correlated to the progression of the disease (17).
Tumor location on the trunk usually have a worse prognosis than those on the head and neck (14).
Although systemic involvement indicates a poor prognosis and regression of Merkel cell carcinoma is exceedingly rare, almost 10 cases of spontaneous regression are present in literature (6).

References

1) Akosa AB, Nield DV, Saad MN: Merkel cell carcinoma: a clinico-pathological report of 3 cases. Br J Oral Maxillofac Surg 1994 Apr; 32(2):111-3.

2) Allen PJ, Zhang ZF, Coit DG: Surgical management of Merkel cell carcinoma. Ann Surg 1999; 229: 97-105.

3) Bielamowizc S, Smith D, Abemayor E: Merkel cell carcinoma: an aggressive skin neoplasm. Laryngoscope 1994; 104:528-532.

4) Bischof M, van Kampen M, Huber P, Wannenmacher M: Merkel cell carcinoma: the role of radiation therapy in general management. Strahlenther Onkol 1999 Dec; 175(12):611-5.

5) Brierley JD, Stockdale AD, Rostom AY: Merkel cell (trabecular) carcinoma of skin treated by radiotherapy. Clin Oncol (R Coll Radiol) 1991 Mar; 3(2): 117-8.

6) Brown TJ, Jackson BA, MacFarlane DF, Goldberg LH: Merkel cell carcinoma: spontaneous resolution and management of metastatic disease. Dermatol Surg 1999; 25:23-25.

7) Crown J, Lipzstein R, Goldsmith M et al.: Chemoterapy of metastatic Merkel cell cancer. Cancer Investigation 1991; 9:129-132.

Datta CK, Mendoza CB Jr: Merkel cell carcinoma: an aggressive neoplasm. W V Med J 1999 May-Jun; 95(3):127-9.

9) Goepfert H, Remmler D, Silva E, et al: Merkel cell carcinoma of the head and neck. Arch Otolaryngol 1984; 110:707-712.

10) Gollard R, Weber R, Kosty MP, Greenway HT, Massullo V, Humberson C: Merkel cell carcinoma: review of 22 cases with surgical, pathologic and therapeutic considerations. Cancer 2000 Apr 15; 88(8):1842-51.

11) Haag ML, Glass LF, Fenske NA: Merkel cell carcinoma. Diagnosis and treatment. Dermatol Surg 1995 Aug;21(8):669-83.

12) Hanke CW, Conner AC, Temofeew RK, et al: Merkel cell carcinoma. Arch Dermatol 1989; 125:1096-1100.

13) Hill ADK, Brady MS, Coit DG: Intraoperative lymphatic mapping and sentinel lymph node biopsy for Merkel cell carcinoma. Br J Surg 1999; 86:518-21.

14) Lawenda BD, Thiringer JK, Foss RD, Johnstone PA: Merkel cell carcinoma arising in the head and neck: optimizing therapy. Am J Clin Oncol 2001 February; 24(1): 35-42.

15) Mazzara CA, Jahn AF, Mirani J: Pathologic diagnosis: Merkel cell carcinoma. Arch Otolaryngol Head Neck Surg 1992; 118:440-442.

16) Medina-Franco H, Urist MM, Fiveash J, Heslin MJ, Bland KI, Beenken SW: Multimodality treatment of Merkel cell carcinoma: case series and literature review of 1024 cases. Ann Surg Oncol 2001 April; 8(3): 204-8.

17) Metzinger SE, Wolfer RS, Disa JJ, Kupersmith JE, Robertson BC: Recurrent Merkel cell carcinoma of the upper extremity. South Med J 2000 March; 93(3):340-5.

18) Nathu RM, Mendenhall WM, Parsons JT: Merkel cell carcinoma of the skin. Radiat Oncol Investig 1998; 6(5): 233-9.

19) Penn I, First MR: Merkel’s cell carcinoma in organ recipients: report of 41 cases. Transplantation 1999 Dec 15; 68(11):1717-21.

20) Pergolizzi J Jr, Sardi A, Pelczar M, Conaway GL: Merkel cell carcinoma: an aggressive malignancy. Am Surg 1997 May; 63(5):450-4.

21) Queirolo P, Gipponi M, Peressini A, et al: Merkel cell carcinoma of the skin. Treatment of primary, recurrent and metastatic disease: review of clinical cases. Anticancer Res 1997 May-Jun; 17(3C):2339-42.

22) Rice RD, Chonkich GD, Thompson KS, et al: Merkel cell tumor of the head and neck. Arch Otolaryngol Head Neck Surg 1993; 119:782-786.

23) Sharma D, Flora G, Grunberg S: Chemoterapy of metastatic Merkel cell carcinoma: case report and review of the literature. Am J Clin Oncol 1991; 14:166-169.

24) Tai Pt, Yu E, Tonita J, Gilchrist J: Merkel cell carcinoma of the skin. J Cutan Med Surg 2000 October; 4(4): 186-95.

25) Toker C: Trabecular carcinoma of the skin. Arch Dermatol 1972; 105:107-110.

26) Warner TFCS, Uno H, Hafez GR, et al: Merkel cells and Merkel cell tumors: ultrastructure, immunochemistry and review of the literature. Cancer 1983; 52:238-245.

27) Wynne CJ, Kearsley JH: Merkel cell tumor. Cancer 1988; 62:28-31.

28) Yiengpruksawan A, Coit DG, Thaler HT, Urmacher C, Knapper WK: Merkel cell carcinoma. Prognosis and management. Arch Surg 1991 Dec; 126(12):1514-9.

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Merkel cell carcinoma is a skin cancer with 30% mortality and an incidence that has tripled in the past 15 years. There is agreement that surgical excision with negative margins is an appropriate therapeutic first step and that sentinel lymph node biopsy is a powerful prognostic indicator. Following excision of detectable cancer, optimal adjuvant therapy is not well established. A role for adjuvant radiotherapy is increasingly supported by retrospective data suggesting a nearly four-fold decrease in local recurrences if radiation is added to surgery. In contrast, a role for adjuvant chemotherapy is not well supported. The rationale for chemotherapy in this disease is based on small-cell lung cancer, a more common neuroendocrine tumor for which chemotherapy is the primary treatment modality. Several issues call into question the routine use of adjuvant chemotherapy in Merkel cell carcinoma: lack of evidence for improved survival; the associated morbidity and mortality; important differences between small-cell lung cancer and Merkel cell carcinoma; and rapid development of resistance to chemotherapy. Importantly, chemotherapy suppresses immune function that plays an unusually large role in defending the host from the development and progression of Merkel cell carcinoma. Taken together, these arguments suggest that adjuvant chemotherapy for Merkel cell carcinoma patients should largely be restricted to clinical trials.

Merkel cell carcinoma is a neuroendocrine cancer that typically presents as a rapidly growing non-specific nodule on sun exposed skin in people over 65 years of age. The recent increase in incidence to over 1000 cases a year in the United States has led Merkel cell carcinoma to become the second most common cause of non-melanoma skin cancer death.^1,2 Optimal management for Merkel cell carcinoma beyond surgical excision is not agreed on, and no randomized trials have been carried out. Sentinel lymph node biopsy has been shown to be powerful in predicting subsequent recurrences as well as in determining if further nodal treatment is indicated.^3,4

Adjuvant radiotherapy is associated with a marked decrease in local recurrences and a trend to improved survival in multiple retrospective studies. Although no prospective trials of radiation therapy have been performed, many retrospective studies find that adjuvant radiotherapy is associated with better outcomes in MCC. A meta-analysis was carried out on 1254 Merkel cell carcinoma patients previously reported in the literature who met the following criteria: a single primary tumor arising on skin that was excised with negative surgical margins on whom follow-up data was included regarding recurrence and survival.⁵ In this study, patients who received adjuvant radiation therapy had improved outcomes compared to those who received surgical excision only. Specifically, local recurrences at 5 years were three times less likely (12% vs 39%, p < .001) if adjuvant radiation was given, and a similar association was found for regional recurrences (23% vs 56%, p < .001) (see Figure 1). Patients who received adjuvant radiation also had an improved overall and cause specific survival, although this was not statistically significant. In a subgroup analysis excluding single-patient case reports and non-comparative studies there was a significant cause-specific survival advantage associated with adjuvant radiation to the local site (hazard ratio for death = 0.62, p = 0.04). Although one large single institution study did not find a statistically significant improvement in outcomes if radiation therapy was given, only 13% of patients in this study received adjuvant radiation and those that received surgery mono-therapy had exceptional results with only 8% experiencing local recurrences.⁴ Although retrospective and not randomized, in aggregate these studies strongly suggest improved outcomes in Merkel cell carcinoma with the addition of adjuvant radiation therapy.

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