Flow cytometry immunophenotyping of vitreous specimens does not contribute to diagnosis of lymphoma without supporting morphologic features

Background: Diagnostic vitrectomy with flow cytometry immunophenotyping (FCI) is being increasingly used as part of screening for diagnostically challenging cases. We aim to evaluate the utility of combined cytopathology and FCI in diagnostic pars plana vitrectomy. We also aim to evaluate cytologic features that could potentially predict FCI outcomes. This study provides clearer indications for use of FCI in diagnostic vitrectomy.

Methods: A case series of diagnostic pars plana vitrectomy specimens from 2010 to 2016 from a single institution was retrospectively evaluated. Associations between cytologic features and FCI were analyzed statistically.

Results: Ninety-nine vitrectomy specimens (90 patients) were evaluated. Evaluation was diagnostic in 39 of 99 (39.4%) specimens. FCI was performed in 66 of 73 (90.4%) specimens collected for lymphoma indication, and 9 of those 66 FCIs (13.6%) demonstrated abnormal lymphocytes. FCI was performed in 10 of 26 (38.5%) specimens collected for non-lymphomatous indications; all 10 FCIs failed to demonstrate lymphocyte abnormality. The absence of large lymphocytes frequently demonstrated negative FCI (negative predictive value = 97.7%), and was the sole cytologic feature significantly associated with a negative FCI result [OR, 14.0; 95% CI, 1.65-635.6; P = .034].

Conclusions: Diagnostic vitrectomy with cytopathology evaluation is valuable, and concomitant FCI is useful to confirm intraocular lymphoma. However, the absence of large lymphocytes on cytologic examination is the single significant predictor of a negative FCI, and this finding should preclude the use of FCI.