Next up is Dr. Oya, who is the recipient of the INS-CNS Joint Section on Tumor Skull Base Award. Congratulations. Well, my name is Soichi Oya from Saitama Medical University, Japan. This is my COI. We know the maximum safe resection is the best policy for most meningiomas, which cannot be replaceable by any other treatment modalities. However, we also know at the same time that the biological features of tumors have more influence on the tumor recurrence rates and the overall prognosis than the extent of resection. To understand the biological characteristics of each tumor, we integrate this information and sometimes change our surgical strategy regardless of whether it is theoretically or instinctively. Among this information, I think the MIB1 Labeling Index is the most important. We have reported that the MIB1 Labeling Index is a key to predict recurrence. However, there are some drawbacks in using it. Firstly, it is not available during surgery. We cannot change, we cannot reflect the result of the MIB1 staining index on our surgical strategy. Secondly, it's not quantitative or reproducible as we want it to be. That's probably because there might be some difference of proliferation potential, even inside the tumor. Also, because of the limited quantitativeness, it's not determined yet how we should utilize the information. Using this technique, intraoperative flow cytometry, we can count the number of cells from a specimen and evaluate the DNA content of each cell. And we need only two millimeter sized specimen and it takes only eight minutes using this preparation kit developed by Nihon Koden Corporation. These are the actual data. The first peak means the euploid cell with the normal DNA content. And the second peak stands for the aneuploid cells with the double DNA content. And we defined the proliferation index as the percentage of aneuploid cells among whole cells. And this technique was originally reported to rapidly determine the glioma cell presence and its histopathological grade. And this is a summary of our patients. We prospect we collected 118 specimens from 50 patients. The tumor size was 2.5 centimeter or larger in 36 patients. 20% was the WHO grade two or higher. And the MIM-MIM1 labeling index was 3.5%. And first of all, there was a positive correlation between the proliferative index and the MIM-MIM1 labeling index as shown here. We next investigated the correlation between proliferative index and annual growth rate. Preoperative sero-MR images were available in 17 tumors. So we have conducted the volumetric analysis for these 17 tumors. And found that the tumors with higher proliferation index are more likely to show, more likely to have higher growth rate. We next studied the intratumoral heterogeneity of this proliferation index. We set the regions of interest like point A for the attachment, point B for the center, point C for the peripheral for large tumors. And type A tumors are those with the highest proliferation index at the attachment. And if the proliferation index was highest at the center or peripheral, we call them non-type A tumors. This graph shows non-type A tumors were statistically significantly associated with a higher annual growth rate. And also, as for peritumoral edema, non-type A tumors were more frequently associated with peritumoral edema than type A tumors. I think our data demonstrate two novel findings. A rapid intraoperative flow cytometry can become a substitute for MIM-1 labeling index, which may help us balance maximum dissection and functional preservation. And also, intraoperative flow cytometry revealed the intratumoral heterogeneity and its relevance to tumor behavior. This indicates the importance to precisely assess the residual portion. For example, this is asymptomatic parasympathetic meningioma. I believe that most neurosurgeons would think that this tumor is going to be a grade WHO grade 2 or higher. And actually, there was severe pile invasion like this. However, the intraoperative flow cytometry showed a relatively low proliferation index, like 4.8%. So we just decided to leave a small mass onto the artery to the motor cortex. And we focused more on the aggressively section of the affected folks. Actually, the postoperative pathological diagnosis was a WHO grade 1 meningioma. And MIM-1 labeling index was 2.3%. So we could achieve SIMPSON grade 3 resection for this patient without any serious complications. And this meningioma encased the M1-M2 bifurcation on the left side. And actually, the tumor was extremely stiff and completely engulfed the M1-M2 bifurcation. So this was a tough tumor. This is M1, and these are M2 branches. And the specimen from here showed the high proliferation index. However, specimen from the M1-M2 bifurcation showed a much lower proliferation index like this. So we decided to shave off the tumor as much as possible. And we left a small mass, small residual, onto the M1-M2 bifurcation rather than being too radical. And our postoperative MIM-1 labeling index findings were consistent with intraoperative flow cytometry. There are some limitations. And I think the direct correlation of our proliferation index and the recurrence rate should particularly be confirmed based on the long-term flow up. As future perspectives, because this is rapid, we may be able to modify our surgical strategy during surgery. And because this is highly quantitative, intraoperative flow cytometry may contribute to the selection of patients who may benefit from our upfront radiosurgery. In conclusion, this method was useful as a substitute for MIM-1 labeling index. And also, this method revealed the intratumoral heterogeneity in meningioma cell proliferation ability and its relevance to tumor behavior. Thank you very much. Thank you.

intraoperative flow cytometry

MIB1 labeling index

meningioma surgeries

tumor specimens

proliferation index