Answer of Dermatopathology Case 53

Immunohistochemistry: Cytokeratin20

Merkel Cell Carcinoma

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Abstract:

New insights into merkel cell carcinoma. Adv Anat Pathol. 2010 May;17(3):155-61.

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

Updated review of the pathogenesis and management of Merkel cell carcinoma.J Cutan Med Surg.2010 Mar-Apr;14(2):51-61.

BACKGROUND: Merkel cell carcinoma is a rare, aggressive, malignant cutaneous tumor of the elderly or immunosuppressed individuals that usually appears on sun-exposed areas of the body. Its pathogenesis is still debated, and, currently, no standardized treatment exists. OBJECTIVE: To provide a current updated review of the most relevant data concerning the pathogenesis and management of Merkel cell carcinoma. METHODS: Using relevant MeSH terms, we performed a review of the literature on these subjects from 1980 to June 2009. RESULTS AND CONCLUSION: The current management of Merkel cell carcinoma is based on surgical excision as the majority of patients present with localized disease, whereas up to 30% have regional lymph node metastases. In these cases, the best outcome is achieved with multidisciplinary management that includes radiotherapy. Chemotherapy is part of the treatment in advanced cases and is mandatory for distant metastatis. Given that a recent work showed the presence of a previously unknown polyomavirus, which the authors called Merkel cell polyomavirus, the therapeutical approach to Merkel cell carcinoma could be reconsidered in the future.

Merkel cell carcinoma: a review of current advances. J Natl Compr Canc Netw.2009 Mar;7(3):333-9.

Merkel cell carcinoma (MCC) is a rare but aggressive cutaneous malignancy of neuroendocrine origin. Its incidence has tripled over the past 15 years. This article reviews the recent advancement in diagnosis, discoveries in pathogenesis, and updates in management. The acronym, AEIOU, has been proposed to aid in clinical identification. In addition to cytokeratin 20, newer immunohistochemical stains (in particular thyroid transcription factor-1 and neurofilament protein) have proven to be essential in pathologic diagnosis. Although immune suppression and ultraviolet radiation have long been associated with the MCC oncogenesis, recent studies also show involvement of a new polyomavirus and bcl-2. Several tumor classifications have been published in the literature, with the 4-tiered system from Memorial Sloan-Kettering Cancer Center the most widely used. A similar classification with additional distinctions among nodal disease is being constructed. A multidisciplinary treatment algorithm is recommended for MCC. Surgical excision with adjuvant radiotherapy (RT) is indicated for localized tumors. RT is favored over complete lymph node dissection and chemotherapy for regional lymph node involvement. For distant metastasis, management should be individualized with a combination of palliative surgery, RT, and chemotherapy.