PMC9805627_01
Axial (a) and sagittal (b) views of enhanced T1-weighted magnetic resonance imaging demonstrating a homogenous enhanced lesion in the dorsal midbrain and a skipped lesion in the right thalamus. The lesion exhibits low intensity on the diffusion-weighted image (c). In the fluid-attenuated inversion recovery image, the lesion is isointense and is accompanied by perifocal edema (d). Positron emission tomography reveals 18F-FDG uptake in the lesion (e).
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F1
In the midbrain lesion, 18F-fluorodeoxyglucose (18FDG) accumulation was also observed on 18F-FDG-positron emission tomography [Figures 1a-e].
Microscopic intraoperative view of the tumor. The surface of the right upper colliculi is partially swollen and pinkish, and recognizable as a lesion (area surrounded by four arrows). The fourth segment of the posterior cerebral artery (P4) and the basal vein of the Rosenthal are also seen.
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F2
The superior colliculus was mildly enlarged, and the surface was discolored, appearing pale pink [Figure 2].
Histopathological findings showed large undifferentiated tumor cells with prominent nucleoli (b, arrow) and small lymphocytes by hematoxylin and eosin staining, presenting a so-called "two-cell pattern" (a and b). Immunohistochemical staining showed that the cell membrane and cytoplasm were positive for C-kit staining (c), and the cell membrane was positive for placental alkaline phosphatase immunostaining (d).
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F3
Pathological examination revealed undifferentiated cells with a large round nucleus and prominent nucleoli associated with small lymphocytic infiltration, suggesting a germ cell tumor [Figures 3a and b]. Immunohistochemically, the atypical cells were positive for C-kit and placental alkaline phosphatase [Figures 3c and d].
Dose distribution of whole-ventricle irradiation (a). Axial (b) and sagittal (c) views of enhanced T1-weighted following completion of chemoradiation therapy. The enhanced lesion disappears. The FLAIR image after 5 years of treatment reveals no recurrence or late radiation morbidity (d).
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F4
Immediately after completing the entire course, MRI confirmed the disappearance of the contrast-enhancing lesions [Figures 4b and c]. No late radiation morbidity such as leukoencephalopathy was observed [Figure 4d].