Bilateral Primary Merkel Cell Carcinoma of the Upper Lid Misdiagnosed as Basal Cell Carcinoma

Merkel cell tumour is a rare primary malignant tumour of the skin that can affect the lids and periocular region. It has a high rate of recurrence and metastasis following surgical excision and an overall mortality rate of 20-33%. Clinically, it is difficult to distinguish from other malignancies and the diagnosis requires careful histological analysis and immunocytochemical staining. A case of Merkel cell tumour affecting the lids and originally misdiagnosed is presented. Correct diagnosis was made only after the appearance of a second Merkel cell tumour on the contralateral lid. The pathogenesis, clinical progression, histology and management of this difficult condition are reviewed.