Fig. 1

a–j Pathology procedure. First, the specimen was collected from surgery (a) and fixed in formalin. The dimensions of the specimen, both before and after fixation were recorded to determine the area retraction (b, c). Then, referring to the MR imaging (d, e), the edges of the specimen were inked with different colors to indicate the original orientation in the brain (f). Subsequently, the specimens were sectioned into 3 mm thick slices (g, h), which ensured that each specimen slice matched the MR slice (i). Finally, sections were embedded in paraffin and cut into 5 μm thick sections, which were stained with H&E and antibodies for immunohistochemistry (j). k Representative example of ME measurement. Left: Image of the slide without magnification. The tumor border was outlined in black. Right: Magnified H&E view (×40) shows invasive tumor cells (blue arrow) outside the primary tumor border. The red line represents the size of the microscopic tumor extension. A, anterior; P, posterior; S, skull; F, falx; L, left; R, right; CR, cranial; CA, caudal; T, tumor; B, tumor border