Merkel cell carcinoma: Prognostic and therapeutic considerations

Merkel cell carcinoma (MCC), first described in 1972 by Toker, is an unusual malignant skin tumor that arises from neuroendocrine cells located in the basal layer of the epidermis. The diagnosis of MCC is difficult because its clinical appearance is often that of an erythematous nodule with regular margins. MCC mainly occurs in people older than 65 and is most frequently located in the head and neck (50%) followed by the extremities (40%) and trunk (10%). Its low frequency in the general population does not allow us to have a prognostic consensus and therapeutic guidelines especially for localized forms of this disease. Based on our clinical experience and on a review of the literature, we can suggest that the behaviour of MCC depends on its initial clinical presentation and on adequate treatment. Tumour size, early growth or presence for six weeks or longer, localization in the head and neck regions and histological aggressivity result as unfavourable prognostic factors. In the authors' opinion, therefore sentinel lymph node (SLN) radiolocalization can improve the stadiation of this neoplasm which principally disseminates through the lymphatic system because it allows us to identify occult metastatic nodal disease in a clinically negative basin, and therefore may facilitate staging of these patients. The SLN technique can provide a precise indication for therapeutic lymphadenectomy when the SLN is positive. The role of CT and XRT in advanced stages remains controversial. Therefore, the treatment regimen chosen for MCC depends on the stage of the disease, and a wide excision of the tumour is always recommended.