Primary intraocular lymphoma: clinical, cytologic, and flow cytometric analysis. 
To compare cytologic with flow cytometric results of vitreous biopsy specimens obtained to rule out primary intraocular lymphoma (PIOL).  Prospective noncomparative case series.  Patients suspected of having PIOL who underwent vitreous biopsy were evaluated.  Patients underwent a standard 3-port vitrectomy and vitreous biopsy to rule out PIOL.  Each undiluted specimen was split, and half was prepared for cytologic evaluation with the collodion bag method; the other half was submitted for flow cytometric immunophenotyping (FCI).  The diluted specimen was processed as a cell block for cytology.  Final diagnosis based on cytology and FCI.  Ten of 14 patients had sufficient specimens for both cytologic and FCI evaluation.  Three patients had chronic inflammation confirmed by both methods.  Six patients had large cell lymphoma identified by both cytology and FCI.  Two of those 6 patients initially had insufficient specimen for FCI.  One patient had large cell lymphoma diagnosed cytologically that was initially negative for a clonal population by FCI.  All lymphomas were B-cell type.  Cytologic evaluation is an accurate diagnostic technique to evaluate for PIOL.  FCI is useful for immunophenotyping PIOL.  Multiple biopsies may be required to achieve a diagnosis.