Primary Visceral Merkel Cell Carcinoma: A Case Report and Review of the Literature

A Primary Extracutaneous Presentation of Merkel Cell Carcinoma

Merkel cell carcinoma (MCC) is a rare aggressive cutaneous neuroendocrine malignancy with a mortality rate of around 33%. The presence of advanced disease at the time of diagnosis is associated with poor prognosis. Twofold etiologies have been described in the pathogenesis of Merkel cell carcinoma: chronic exposure to ultraviolet (UV) light and Merkel cell polyomavirus (MCPvY). MCC usually affects sun-exposed skin areas, and the presence of cutaneous nodules is the hallmark of the disease. However, there have been case reports in the literature where the diagnosis of MCC was made in the absence of any cutaneous findings. We present a case report of Merkel cell carcinoma that is unique in its presentation because of the presence of pulmonary and hepatic nodules and the absence of cutaneous lesions.

New perspectives in Merkel cell carcinoma

PURPOSE OF REVIEW

Merkel cell carcinoma (MCC), a rapidly progressing skin cancer, has poor prognosis. We reviewed the epidemiology, pathogenesis, diagnosis and treatment of MCC, with a focus on recent therapeutic advancements.

RECENT FINDINGS

Risk factors for MCC, such as old age, immunosuppression, polyomavirus infection and exposure to UV radiation have already been identified, but the underlying mechanisms leading to carcinogenesis still need clarification. On the basis of recent advances, immunotherapy - in particular, inhibition targeting the programmed cell death protein 1/programmed death-ligand 1 (PD1)/PDL1) immune checkpoint blockade - is currently being investigated in the treatment of metastatic MCC. Avelumab, an anti-PDL1 antibody, was the first drug to be approved internationally as second-line monotherapy for patients with advanced MCC, based on results from the JAVELIN Merkel 200 clinical trial. Avelumab has also recently been approved as first-line treatment for advanced MCC in Europe. Pembrolizumab (anti-PD1) in first-line and nivolumab (anti-PD1) in first-line and second-line treatments are two other checkpoint inhibitors that are under investigation, and showing promising results. New innovative therapies are also in development.

SUMMARY

New insights concerning advances in MCC diagnosis and treatment have been highlighted. Immunotherapy for metastatic MCC constitutes a recent breakthrough in an unmet medical need, but alternative therapies should continue to be investigated.