Gene expression profiling of primary vitreoretinal lymphoma

The characteristics of tumor cells of primary vitreoretinal lymphoma (PVRL) have not been defined, although researches have shown that most cases are of diffuse large B-cell lymphoma (DLBCL). To determine the subtype and biological characteristics of tumor cells of PVRL, we performed a gene expression profiling analysis. RNA was extracted from the vitreous fluid of 7 PVRL patients and from nodal samples of 10 DLBCL patients: 6 of germinal center B-cell (GCB) type and 4 of activated B-cell (ABC) type determined by Hans' criteria. Six PVRL samples showed gene expression profiles that were similar to each other. The patterns were different from those of the ABC-type nodular DLBCL but relatively close to those of the GCB-type nodular DLBCL. Interestingly, all of the 6 examined PVRL samples had either MYD88(L265P) or mutation in the immunoreceptor tyrosine-based activation motif (ITAM) region of CD79B. Five PVRL patients with similar gene expression profiles were treated with a standardized regimen: intravitreal administration of methotrexate (MTX) followed by six courses of systemic high doses of MTX. As a result, 2 patients had CD79B mutations and showed early central nervous system (CNS) progression. Patients without CNS progression did not have this mutation. In conclusion, PVRL had unique genetic features: an expression pattern different from ABC-type and relatively close to GCB-type DLBCL. CD79B mutations showed potential to serve as prognostic markers for CNS progression.