Merkel Cell Carcinoma: New Trends

Abstract

Merkel cell carcinoma (MCC) is a rare neuroendocrine tumor of the skin mainly seen in the elderly. Its incidence is rising due to ageing of the population, increased sun exposure, and the use of immunosuppressive medication. Additionally, with the availability of specific immunohistochemical markers, MCC is easier to recognize. Typically, these tumors are rapidly progressive and behave aggressively, emphasizing the need for early detection and prompt diagnostic work-up and start of treatment. In this review, the tumor biology and immunology, current diagnostic and treatment modalities, as well as new and combined therapies for MCC, are discussed. MCC is a very immunogenic tumor which offers good prospects for immunotherapy. Given its rarity, the aggressiveness, and the frail patient population it concerns, MCC should be managed in close collaboration with an experienced multidisciplinary team.

Keywords: Merkel cell carcinoma; biomarkers; immunotherapy; radiotherapy; surgery.

Figure 1

Ninety-four-year-old lady with Merkel cell carcinoma (MCC) of the right cheek, treated with radiotherapy (48 Gy). (A) Before treatment; (B) after 8 fractions (32 Gy); (C) after 12 fractions (48 Gy); (D) 6 weeks after completion of radiotherapy.

Figure 2

CT-scans of a 66-year-old man with massive lymphogenic metastases in abdomen and pelvis (short arrows) progressive under avelumab. Subsequent treatment with radiotherapy and restart of avelumab in last week of radiotherapy. (A) Before radiotherapy, note bilateral hydronephrosis (long arrows); (B) two months after radiotherapy (13 × 3 Gy), complete regression and recovery of hydronephrosis; (C) two years after radiotherapy; persistent complete regression.