Evaluation and management of lymph node metastasis should be performed in all patients with MCC, because lymph node metastasis develops in up to 75% of patients. But, Routine performance of elective lymph node dissection (ELND) is cur­rently considered controversial because of potential morbidity, without proven survival benefit. Many recent studies suggest that, as alternative method, sentinel lymph node (SLN) mapping and biopsy could improve the ability to detect subclinical nodal metastases, sparing those patients with negative nodes the morbidity of lymph node dissection. SLN mapping and biopsy could provide a more accurate prognostic information for patients. Sheela G et al. recently suggested that SLN biopsy should be routinely included in the evaluation of patients with MCC.

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Merkel cell carcinoma (MCC) typically presents as a solitary dome-shaped, deep red to violaceous nodule or indurated plaque and tends to have a shiny surface, often with overlying telangiectasia. The overlying skin is usually intact. Histologically, anastomosing cords and strands of neoplastic cells are seen in the dermis and subcutis, but not in the epidermis. The individual cells are monomorphous with round vesicular nuclei and scanty, ill-defined cytoplasm. Ultrastructurally the tumor cells are characterized by the presence of paranuclear fila­ment whorls and membrane-bound neurosecretory granules approximately 100 ~ 150 nm across. Immu- nohistochemistry is an important tool in the dia­gnosis of MCC. The tumor cells have epithelial and neural properties because coexpression of cytokeratin filaments and neurofilaments can be observed. Immunohistochemical study results are positive for neuroendocrine markers (chromogranin, synapto- physin, neurospecific enolase and neurofilaments), low molecular weight cytokeratins and membrane epithelial antigen. Especially, perinuclear dot-like staining for cytokeratin 20 is a characteristic finding.

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A 73-year-old man had a 2-month history of a rapidly growing painless mass on the left upper arm.

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INTRODUCTION

Merkel cell carcinoma (MCC), also referred as neuroendocrine or trabecular carcinoma, is an uncommon malignancy originally described by Toker in 1972. Although the exact origin of the Merkel cell is unknown, it probably arises from neuro¬endocrine cells between the basal epidermis and then grows vertically into the dermis and sub¬cutaneous tissue. It usually arises in the head and neck area and extremities of elderly people as a nodule or plaque lesion. Cases of MCC have a poor outcome characterized by locoregional and distant relapse. It has been reported that 34% of affected patients die because of the tumor. Recent evidences suggest that surgery and adjuvant locoregional radiotherapy may produce a better disease-free survival compared with surgery alone. Read the rest of this entry »