Comparative DNA Flow Cytometric Study of Primary Intraocular and Central Nervous System Lymphomas

Abstract

Primary intraocular lymphoma is generally considered as a subset of primary CNS lymphoma. This study attempts to show that they may in fact represent distinct entities by comparing their respective proliferation rates using DNA flow cytometry. Four samples of primary intraocular lymphoma and seven samples of primary CNS lymphoma were analyzed, all from paraffin-embedded tissue. All tumors were of the large B-cell type. A normal human tonsil sample was used as a control. Tissue samples were analyzed by DNA flow cytometry, which is a precise and objective method to measure DNA content and cell proliferation of a tumor. S-phase fraction (SPF) and DNA content were measured for each sample. The average SPF for primary intraocular lymphoma was significantly higher than that of primary CNS lymphoma, 23.8 (range: 18.9 to 29.6) versus 15.1 (range: 1.1 to 25.1) respectively. Of the 11 tumors analyzed, 2 brain tumors were aneuploid and 1 eye tumor was peridiploid. All other tumors were diploid. Thus, no significant pattern was detected in the DNA content of the tumors. This lack of clinical significance of tumor aneuploidy is consistent with data reported in the literature. The results of this study indicate that primary intraocular lymphoma is more aggressive and of higher grade than primary CNS lymphoma. The different proliferation rates of intraocular and CNS lymphomas may be explained by either their different spatial location or a distinct genetic composition, the latter reinforcing the hypothesis that the two are fundamentally different entities