Orbital and Adnexal Lymphoproliferative Lesions

Ocular adnexal lymphoproliferative disease (OALD) is a general term for the spectrum of lymphoproliferative tumours of the ocular adnexa (OA). The OA comprise the eyelids, conjunctiva, lacrimal apparatus, and orbital soft tissues. Benign OALD is a reactive lymphoid hyperplasia (RLH) of polyclonal small B cells and T cells. Any type of lymphoma can involve the OA. Malignant lymphomas are classified according to the presumed cell of origin as defined by the World Health Organization (WHO) Classification of Tumours of Haematopoietic and Lymphoid Tissues [1], of which the updated fifth edition is yet to be published at the time of writing this chapter. Lymphomas can be divided into two major groups: Hodgkin lymphoma and non-Hodgkin lymphoma (NHL). Because Hodgkin disease of the OA is extremely rare, it will not be discussed here. Primary ocular adnexal lymphoma (OAL) is defined as a lymphoma of the OA without evidence of concurrent systemic lymphoma and no prior history of lymphoma. Primary OAL should be staged according to the TNM classification devised for OAL (Table 1) because the TNM-based staging system better predicts outcome in OAL than the Ann Arbor system [2].