Ocular involvement of leukemic cells is an uncommon clinical finding but can appear as either a presenting sign of disease or a first sign of relapse. Involvement can be classified as either “primary” or direct infiltration of leukemic cells or “secondary” or indirect involvement due to inflammatory reaction or treatment effects. Leukemic infiltration of the anterior chamber (i.e.. iris, uvea) is more common in acute lymphoblastic leukemias than other myeloid malignances. The retina is the most common site, with about 70% of patients having ocular involvement resulting in retinal hemorrhages or infarcts. So, high clinical suspicion is warranted, especially in patients with new or previously diagnosed leukemia, which may require vitreous or retinal sampling.

Cytological preparation and appropriate triaging of precious specimens such as vitreous fluid is important. Initial evaluation with a Pap-stained ThinPrep can be used to assess cellularity and decide if a cell block is appropriate. Additionally, a cellblock slide with immunostains for CD34 (a blast marker) and TdT (an immature lymphocyte marker) can be used to further characterize the atypical cells. If sufficient volume of fluid is provided, cytological evaluation in combination with flow cytometry or molecular studies can have better diagnostic yield; but cytology alone is amenable for diagnosis when flow is unavailable.