title: Merkel cell carcinoma.
abstract: BACKGROUND
  Merkel cell carcinoma is an aggressive tumor with nonspecific clinical features. The prognosis in general is worse than malignant melanoma. Local recurrence rates are high with one-third of patients having recurrence within one year of excision. The tumor invades blood vessels and lymphatics. This frequent lymphatic dissemination leads later to satellite lesions and recurrence. Distant metastases occur in one-third of patients. One-,two- and three-year survival rates are poor, being estimated at 88%, 72%, and 55%, respectively.
  
  
  OBJECTIVE
  To increase awareness of the behavior of this uncommon tumor.
  
  
  METHODS
  A review of the current literature and recommendations regarding this tumor.
  
  
  RESULTS
  Wide local excision with 3-cm margin shows significant reduction in local recurrence compared with 2-cm margins. Two-thirds of patients with local recurrence ultimately die from their disease. Radiation therapy has a role to play in the local and regional clearance of the tumor.
  
  
  CONCLUSIONS
  Prompt diagnosis and surgical excision are necessary to improve survival. Mohs micrographic surgery offers potential advantages in evaluating both the lateral and the deep margins. Follow-up studies of patients treated with this modality will be beneficial.
authors.affiliation: Department of Dermatology, Mayo Clinic, Rochester, MN 55905, USA.
authors.forename: W J
authors.initials: WJ
authors.lastname: O'Connor
authors.forename: D G
authors.initials: DG
authors.lastname: Brodland
mesh_terms: D015266:Carcinoma, Merkel Cell / Q000175:diagnosis* / Q000209:etiology / Q000628:therapy; D003131:Combined Modality Therapy; D003937:Diagnosis, Differential; D006258:Head and Neck Neoplasms / Q000175:diagnosis* / Q000209:etiology / Q000628:therapy; D006801:Humans; D008207:Lymphatic Metastasis; D011379:Prognosis; D012878:Skin Neoplasms / Q000175:diagnosis* / Q000209:etiology / Q000628:therapy