A reappraisal of the diagnostic and therapeutic management of uncommon histologies of primary ocular adnexal lymphoma.

Lymphoma is the most common malignancy arising in the ocular adnexa, which includes conjunctiva, lachrymal gland, lachrymal sac, eyelids, orbit soft tissue, and extraocular muscles. Ocular adnexal lymphoma (OAL) accounts for 1%-2% of non-Hodgkin lymphoma and 5%-15% of extranodal lymphoma. Histology, stage, and primary localizations are the most important variables influencing the natural history and therapeutic outcome of these malignancies. Among the various lymphoma variants that could arise in the ocular adnexa, marginal zone B-cell lymphoma (OA-MZL) is the most common one. Other types of lymphoma arise much more rarely in these anatomical sites; follicular lymphoma is the second most frequent histology, followed by diffuse large B-cell lymphoma and mantle cell lymphoma. Additional lymphoma entities, like T-cell/natural killer cell lymphomas and Burkitt lymphoma, only occasionally involve orbital structures. Because they are so rare, related literature mostly consists of anecdotal cases included within series focused on OA-MZL and sporadic case reports. This bias hampers a global approach to clinical and molecular properties of these types of lymphoma, with a low level of evidence supporting therapeutic options. This review covers the prevalence, clinical presentation, behavior, and histological and molecular features of uncommon forms of primary OAL and provides practical recommendations for therapeutic management.