Optimal utilization of paucicellular vitreous sample for diagnosis of primary vitreoretinal lymphoma.

Introduction: Primary vitreoretinal lymphoma (PVRL) is a rare, aggressive, and intraocular non-Hodgkin lymphoma, typically manifesting as diffuse large B-cell lymphoma (95%). Vitreous fluid cytology is the gold standard for diagnosis; however, its utility is limited by poor preservation and low cellularity. Recent studies indicate that myeloid differentation primary response protein 88 (MYD88) mutation analysis is more sensitive and accurate on low-cellularity or poorly preserved samples. The incidence of PVRL has reportedly tripled with an annual average of ∼50 cases in the United States. Delayed diagnosis can lead to mortality within 2 years, underscoring the need for improved diagnostic methods.

Materials and methods: We conducted a 5-year retrospective study of vitreous samples from 3 tertiary centers. A cytopathologist and a hematopathologist reviewed the samples and classified them as "negative," "atypical," or "positive." Whole slide imaging (WSI) was incorporated to quantify atypical lymphocytes using an arbitrary cutoff (≥25% considered positive; <25% considered atypical) and to document necrosis and apoptosis. Ancillary tests included flow cytometry, immunohistochemistry (IHC), and MYD88 mutation analysis.

Results: Of the 226 samples, 214 were diagnosed as negative, 6 as atypical, and 6 as positive. WSI enhanced the diagnosis by precisely quantifying atypical lymphocytes. Flow cytometry was conclusive in 2 of 8 cases, IHC in 7 of 8, and MYD88 analysis in 4 of 5 cases.

Conclusions: While cytology remains the gold standard, a combination of WSI, targeted IHC, and MYD88 analysis enhances diagnostic precision in paucicellular samples. Flow cytometry should be reserved for cases with high cellularity and strong clinical suspicion.