PMC10247218_01
Initial brain magnetic resonance (MR) images showing a space-occupying lesion in the medulla oblongata. It was observed in hypointensity on the T1 weighted image (T1WI) (A) and hyperintensity on T2WI (B) but only a minor elevation of signal intensity on the diffusion-weighted image (DWI) (C) and with poor apparent diffusion coefficient reduction (D). It was homogenously enhanced with gadolinium, and axial (E) and sagittal (F) images are shown.
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The MR images showed a homogenously enhancing tumor in the dorsal medulla oblongata (Fig. 1).
A: Intraoperative view of the tumor and the surrounding structure. Note that the tumor (T) is seen at the bottom of the floor of the fourth ventricle (IV) in grayish-red whereas the cerebellar hemisphere (C) is in normal brain color. Arrowhead indicates the obex. B-G: Histopathology of the tumor specimen. Tumor cells with well-defined nuclear atypia and large round to oval nuclei grow densely. Numerous mitotic figures (more than 10 cells/HPF) are observed (B). Immunohistochemical staining is positive for CD20 (C), Bcl-6 (D), and MUM-1 (E) and negative for CD10 (F), indicating a non-GCB-type diffuse large B-cell-type lymphoma. MIB-1 labeling index is more than 90% (G).
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By the exposure of the dorsal surface of the medulla after removing the tela choroidea and lifting up bilateral cerebellar tonsils, a bulging of the tumor covered with a thin ependymal layer in grayish-red was observed (Fig. 2A). Immunohistochemistry for CD20, Bcl-6, and MUM-1 was positive, and that for CD10 was negative (Fig. 2C-F). The MIB-1 labeling index was greater than 90% (Fig. 2G).
MR images 5 months after the biopsy when chemotherapy was finished. By axial T1WI (A), T2WI (B), Gd-T1WI (C), and a sagittal Gd-T1WI (D), no apparent residual tumor can be detected.
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MR images showed the disappearance of the enhancing tumor mass (Fig. 3A-D).