Merkel cell carcinoma metastasis to the iris in a 23 year old female.

Merkel cell carcinoma (MCC) is a rare, aggressive neuroendocrine malignancy which predominantly affects elderly caucasians. The pathogenesis is poorly understood but ultraviolet light and immunosuppression have both been implicated. MCC most commonly arises on sun exposed areas of the head and neck or extremities and has a propensity for local recurrence and regional lymph node metastasis. It may present as a violaceous or non specific firm nodule or as a small plaque. Histological diagnosis can be difficult and electron microscopy or immunohistochemistry are frequently required in addition to light microscopy. Management is stage dependant and frequently involves wide surgical excision with or without chemotherapy or radiation therapy. Early diagnosis and complete surgical excision is associated with a favourable prognosis. However, aggressive tumours with regional recurrence or distant metastases result in a median survival of 9 months. Reports of primary MCC of the eyelids have been reported in the literature. Intra-ocular metastases to the choroid and ciliary body have also been reported.