Merkel cell carcinoma: what do we know about it and what should we do?

Effect of the dual phosphatidylinositol 3-kinase/mammalian target of rapamycin inhibitor NVP-BEZ235 against human Merkel cell carcinoma MKL-1 cells

Merkel cell carcinoma (MCC) is an aggressive skin cancer with an increasing incidence. Aberrant activation of the phosphatidylinositol-3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) pathway is common in human cancers and has been revealed to play an important function in cell proliferation, metabolism and tumorigenesis. In the present study, NVP-BEZ235, a dual PI3K/mTOR inhibitor, was revealed to be effective in inhibiting proliferation and inducing cell cycle arrest in MKL-1 cells. Additional investigations revealed that NVP-BEZ235 attenuated PI3K/Akt/mTOR signaling and upregulated the levels of the cell cycle inhibitors p21 and p27. Overall, the present results possess considerable implications for future development of dual PI3K/mTOR inhibitor as potential agents in the management of MCC.

A rapidly growing lid lump

A 97-year-old woman presented with a 5-month history of a rapidly growing, painless, left upper eyelid lesion. Examination revealed a large vascularised, ulcerated nodule on the left upper lid, causing significant ptosis. Wide local excision of the lesion was performed and the wound was left to heal by secondary intention. Histology and immunohistochemistry of the lesion confirmed a diagnosis of Merkel cell carcinoma, a rare primary malignancy of the eyelid which has significant morbidity and mortality. Although uncommon, this diagnosis should always be considered in any patient with a rapidly growing lid lump. In view of the patient's age, known dementia and family wishes, the patient was managed conservatively, with no further investigations performed. She was due to be followed up in clinic on a regular basis, but has since died from other causes.

[A probable etiological role of Merkel cell polyomavirus in the development of Merkel cell carcinoma]

Approximately 20% of the tumours in humans are associated with contagious viral agents. Merkel cell carcinoma is a rare and highly aggressive tumour which may originate from the epidermal stratum basale, although the origin is still controversial. This tumour is most commonly found in elderly and immunocompromised patients in sun exposed areas, especially in the head and neck regions. Merkel cell carcinoma often causes a diagnostic challenge with a dramatically increasing incidence. In 2008, a DNA tumour virus, a polyomavirus (Merkel cell polyomavirus) was detected in Merkel cell carcinomas, and this finding helped to understand the etiological background of the disease. The infectious - probably viral - etiology resulted in a paradigm shift in pathogenesis and, hopefully, in therapy as well. This review summarizes the current knowledge related to Merkel cell carcinoma and the first oncogenic human polyomavirus, the Merkel cell polyomavirus, to promote the clinical adaptation of the information.