Merkel Cell Carcinoma (MCC)

  • MCC:
    • Also known as primary small-cell carcinoma of the skin and anaplastic carcinoma of the skin:
      • Is a rare, aggressive cutaneous malignancy
  • Risk factors for MCC include:
    • Immunosuppression:
      • Human immunodeficiency virus (HIV) infection
      • Cancer
      • Organ transplant
    • Chemotherapy
    • Radiation
    • Arsenic
    • Sun exposure
  • Approximately 80% of Merkel cell tumors:
    • Harbor a polyoma virus:
      • But its role in pathogenesis remains unclear
  • The cornerstone of management for MCC is:
    • Wide local excision with a margin of 1 to 2 cm
    • Nodal staging in clinically node-negative patients:
      • Is a subject of controversy:
        • About one third of the patients with MCC will have a positive SLN:
          • SLN biopsy does not appear to have an impact on survival but does improve local control
        • On the basis of the current evidence, National Comprehensive Cancer Network guidelines:
          • Recommend routine SLN biopsy for clinically node-negative MCC
  • MCC is an extremely radiosensitive tumor:
    • A recent randomized study for stage 1 Merkel cell carcinoma:
      • Showed significant reduction on regional recurrence with radiation
    • A retrospective Surveillance, Epidemiology, and End Results (SEER) database study:
      • Demonstrated an improvement in survival for patients who received adjuvant radiation:
        • This effect was more pronounced in the 2 cm tumors
      • Recommendations for adjuvant radiation after appropriate surgical resection are still unclear:
        • However, adjuvant radiation therapy to the primary tumor site should be considered for:
          • Larger ( greater than 1 cm) tumors with adverse features such as:
            • Perineural invasion and lymphovascular invasion
        • In high-risk cases that omit a SLN biopsy:
          • Radiation to nodal basin is recommended
      • Regional lymph node dissection and / or nodal irradiation is recommended for patients with nodal metastases;
        • However, for resectable lesions there is no role for neoadjuvant radiation therapy
  • References:
    • Gupta SG, Wang LC, Peñas PF, Gellenthin M, Lee SJ, Nghiem P. Sentinel lymph node biopsy for evaluation and treatment of patients with Merkel cell carcinoma: The Dana-Farber experience and meta-analysis of the literature. Arch Dermatol. 2006;142:685-690.
    • Jouary T, Leyral C, Dreno B, et al. Adjuvant prophylactic regional radiotherapy versus observation in stage I Merkel cell carcinoma: A multicentric prospective randomized study. Ann Oncol. 2012;23:1074-1080.
    • Mehrany K, Otley CC, Weenig RH, Phillips PK, Roenigk RK, Nguyen TH. A meta-analysis of the prognostic significance of sentinel lymph node status in Merkel cell carcinoma. Dermatol Surg. 2002; 28:113-117.Mojica P, Smith D, Ellenhorn JD. Adjuvant radiation therapy is associated with improved survival in Merkel cell carcinoma of the skin. J Clin Oncol. 2007;25:1043-1047.

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