Merkel cell carcinoma

Merkel cell carcinoma (MCC) is a rare cutaneous cancer with a high risk of regional and distant metastases and a higher case fatality rate than melanoma. The primary cutaneous tumour is typically rapidly growing but usually asymptomatic and is often initially misdiagnosed as a benign lesion.

Key risk factors for MCC are advancing age, immunosuppression, and light skin type. Two distinct aetiologies are now recognised: exposure to ultraviolet radiation and oncogenic transformation by Merkel cell polyomavirus (MCPyV).

Diagnosis is confirmed with skin biopsy and histopathological evaluation including immunohistochemistry. Occult metastasis is common, and sentinel lymph node biopsy and imaging are important tools for staging the disease.

Management requires a multidisciplinary approach as evidence is scarce and optimal treatment is not well established. Localised disease is managed with surgical wide local excision with or without radiotherapy. Lymph node disease requires radiotherapy to the nodal basin or lymph node dissection or a combination of the two, with consideration of neoadjuvant or adjuvant immunotherapy. For patients with stage IV metastatic disease, enrolment in a clinical trial (if available) is the preferred option according to US and European guidelines; otherwise, any one or a combination of immunotherapy with an immune checkpoint inhibitor, radiotherapy, or surgery is recommended.

MCC recurs in up to half of patients; hence, ongoing monitoring is important.

​Merkel cell carcinoma (MCC) is a rare, aggressive cutaneous neuroendocrine neoplasm that primarily affects white adults, with incidence increasing with advancing age. MCC carries a high risk of recurrence and locoregional and distant metastases.[1]Lemos BD, Storer BE, Iyer JG, et al. Pathologic nodal evaluation improves prognostic accuracy in Merkel cell carcinoma: analysis of 5823 cases as the basis of the first consensus staging system. J Am Acad Dermatol. 2010 Nov;63(5):751-61. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2956767 http://www.ncbi.nlm.nih.gov/pubmed/20646783?tool=bestpractice.com ​ The primary MCC tumour typically presents as an asymptomatic, rapidly growing, pink-to-violaceous or skin-coloured dermal or subcutaneous nodule on sun-exposed skin.[2]Heath M, Jaimes N, Lemos B, et al. Clinical characteristics of Merkel cell carcinoma at diagnosis in 195 patients: the AEIOU features. J Am Acad Dermatol. 2008 Mar;58(3):375-81. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2335370 http://www.ncbi.nlm.nih.gov/pubmed/18280333?tool=bestpractice.com