MKI67 and cyst: In contrast, the second case was of an atypical meningioma, which is characterized by more blood supply, larger cyst cavity, tumoral infarction, necrotic foci, and mitotic figures, and higher positive rate of tumor immune markers, such as Ki-67, S-100, P53, etc. Consequently, we considered that the pathomorphological mechanisms of cystic changes in current cases may be correlated to the secretion activity of the cystic tumor cells, infarction and necrosis of tumor tissue, peripheral brain edema, and loculated widened subarachnoid space.