Diagnosis of PIOL can be challenging. It requires a high degree of clinical suspicion and differential diagnosis includes infectious and non-infectious etiologies particularly the common masquaraders sarcoidosis, tuberculosis, viral retinitis and syphilis. The definitive diagnosis depends on demonstration of malignant lymphoma cells in ocular specimens or CSF. Ocular specimen could include vitreous, aqueous or chorioretinal biopsy. Ocular pathologist should be consulted prior to the diagnostic procedure to help handle and process the specimen appropriately. In addition to cytology, flow cytometry, immunohistochemistry, molecular analysis and cytokines may be used as adjuncts in facilitating the diagnosis.