Flow cytometry, cytology and histology in the diagnosis of ocular hematologic neoplasms: a 15-year monocentric experience with a focus on ocular lymphomas

OBJECTIVES: Ocular lymphomas are rare diseases that occur in ocular adnexa or specific intraocular regions. Although histology remains the gold standard, cytology and flow cytometry (FCM) are fundamental, mainly when a biopsy sampling is technically demanding. This study evaluated the effectiveness of FCM in diagnosing ocular diseases, especially hematologic malignancies, and compared its performance with the other techniques. METHODS: In this monocentric study we collected patient characteristics from 165 patients referred to Padua University Hospital. Sensitivity, specificity, positive (PPV) and negative predictive values (NPV), accuracy and concordance rate were evaluated for cytologic, FCM, and/or histologic analyses performed. RESULTS: Patients were classified as having hematologic neoplasms (n=86), non-hematologic neoplasms (n=33) or non-neoplastic diseases (n=46). Hematologic neoplasms comprised 74 cases with ocular adnexal hematologic lesions and 12 cases with intraocular lymphomas and leukemias. FCM analysis of ocular specimens allowed valuable results in 71/86 hematologic cases, failure being mainly due to absence of cellularity (8/15). Histology showed 100 % PPV for both hematologic and non-hematologic neoplasms; FCM reached 97 and 66 %, and cytology 80 and 91 %, respectively. Concordance between FCM and cytology was lower (κ<0.61) than with histology (κ=0.677). FCM phenotype matched ocular lymphoma histotype in 95.8 % of cases. The lymphocytic infiltrate by FCM was 39.5 % in non-neoplastic, 64 % in non-hematologic and 89.5 % in hematologic diseases with B lymphocyte prevalence of 31.3 %, 21.0 % and 93.3 %, respectively. Clonality analysis remains essential regardless of these values. CONCLUSIONS: FCM provides rapid results, studies numerous markers simultaneously, and analyzes ocular aspirates from minimally invasive samples. For this reason, it is desirable to permanently integrate this technique into the diagnostic process of ocular disorders, particularly when hematologic malignancies are suspected, as part of an integrated multidisciplinary pathway.