Evaluation of vitrectomy specimens and chorioretinal biopsies in the diagnosis of primary intraocular lymphoma in patients with Masquerade syndrome

Purpose. To correlate the histopathological diagnoses established by diagnostic vitrectomy and chorioretinal biopsy in patients with clinically suspected primary intraocular lymphoma (PIOL) or chronic idiopathic uveitis, and the clinical follow-up data. Methods. Eighty-four consecutive pars plana vitrectomy (PPV) specimens, three chorioretinal biopsies and two enucleated eyes taken from 80 patients were evaluated. All PPV specimens were unfixed; these were centrifuged, the "cytospins" being stained conventionally (May-Grunwald-Giemsa) and using immunocytology (CD79a, CD3, CD68, immunoglobulin (Ig) light chains). An extended immunohistochemical panel, as well as polymerase chain reaction (PCR) for rearrangements of the Ig heavy chain gene (IgH-PCR), were used to investigate the chorioretinal biopsies and the enucleated eyes. Diagnoses, made on the basis of morphology and immunophenotype, included "reactive cellular infiltrate", "malignant lymphoma", "suspicious of neoplastic disease", and "insufficient for diagnosis". The corresponding clinical data were collected and compared with the diagnosis. Results. The 80 patients consisted of 46 women and 34 men. The patients' age range varied from 21 to 100 years (mean age 62 years). Sixty-two (74%) of the 84 vitrectomy specimens were diagnosed as "reactive cellular infiltrate", 12 (14%) as definite "malignant lymphoma", 5 (6%) as "suspicious of neoplastic disease" and 5 (6%) specimens were considered "insufficient for diagnosis". An additional chorioretinal biopsy enabled an unequivocal diagnosis of PIOL to be reached in 3 patients. All PIOL were diffuse large cell B-cell lymphoma (DLBCL), with the immunophenotype CD79+, CD20+, BCL-2+, BCL-6+, MUM1+ and monotypical expression for IgM+. A monoclonal IgH-PCR amplification product was obtained in four vitrectomy specimens, two chorioretinal biopsies and one of the enucleated eyes. Comparison of the diagnoses with long-term follow-up clinical data resulted in concordance in 77 (96%) cases and discrepancies ("false-negative" diagnoses) in 3 patients (4%). The patients diagnosed with lymphoma were treated with either radiotherapy, chemotherapy or both. At final follow-up (mean 35 months), 5 patients (6%) had developed cerebral lymphomatous manifestation, and 7 (9%) had succumbed to their disease. Conclusion. The diagnosis of PIOL is often extremely difficult, requiring sufficient rapidly transported good-quality material, and experienced interpretation. Although cytological examination of vitreal aspirates remains the gold standard in diagnosis, examination of chorioretinal biopsies increase the reliability of diagnosing or excluding a PIOL that involves the retina or choroid. Most PIOL are DLBCL with an immunophenotype suggesting a cellular origin from germinal centre cells.