Mantle cell lymphoma (MCL) of the ocular adnexa does not differ from systemic mantle cell lymphoma in its biological and clinical behaviour. As the name suggests, it arises from the mantle zone of the lymphoid follicles. It is a mature B-cell lymphoma, which is much less common than the other subtypes of B-cell lymphomas, and has an aggressive clinical course. It commonly affects men, and more than two thirds of the patients have disseminated disease or bilateral disease at presentation.