Intraoperative Flow Cytometry Enables the Differentiation of Primary Central Nervous System Lymphoma from Glioblastoma.

Objective: Accurate preoperative and intraoperative differentiation between primary central nervous system lymphoma (PCNSL) and glioblastoma (GBM) is sometimes difficult. Distinguishing between these tumors during surgery is important because surgical treatment is different between the 2 tumors. In this study, we established a new method of intraoperative differentiation between PCNSL and GBM using intraoperative flow cytometry (iFC), and we retrospectively tested whether iFC was useful for the intraoperative diagnosis of PCNSL and GBM.
Methods: We analyzed the iFC data of 250 patients (28 with PCNSL and 222 with GBM) and then evaluated aneuploidy and S-phase population.
Results: Aneuploidy was detected in 54.5% of GBM cases but in only 7.14% of PCNSL cases. Aneuploidy indicated GBM, but it was difficult to distinguish PCNSL from GBM when a tumor had a diploid pattern. Thus, for tumors without aneuploidy, we evaluated the S-phase population: S2, the ratio of the average height of the S-phase to the height of the diploid peak. S2 was significantly higher in PCNSL than in GBM. Based on these results, we established an algorithm for differentiating between PCNSL and GBM using DNA aneuploidy and S2. Comparing this new iFC algorithm and the permanent pathologic diagnosis, the sensitivity was 89.3%, the specificity was 93.7%, and the accuracy was 93.2%.
Conclusions: iFC is useful for the intraoperative differentiation between PCNSL and GBM and it aids in intraoperative decision making within a short time. The accuracy of intraoperative diagnosis of these tumors seems to be higher with the combination of iFC and intraoperative rapid pathologic diagnosis.
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