PMC9334767_01
Findings from the first and second magnetic resonance (MRI) imaging of a dog with meningioma. Transverse T2-weighted (A,E), fluid-attenuated inversion recovery (B,F), and post-contrast (C,G) images at the optic chiasm level and sagittal T2-weighted images (D,H). The first MRI scan was performed before chemotherapy. A solitary amorphous mass (2.7 x 1.9 x 2.2 cm) can be observed in the right frontal lobe. The tumor lesion (arrows) shows hyperintensity on T2-weighted (A,D) and fluid-attenuated inversion recovery (B) images. Post-contrast (C) image shows uniformly remarkable enhancement (arrowhead). Second MRI was obtained 355 days after initial chemotherapy (E-H). A more severe midline shift compared with the findings of the first MRI scan can be observed and the size of the tumor increased to 3.5 x 2.8 x 2.9 cm.
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F1
T1-weighted images and hyperintense on T2-weighted (Figures 1A,D) and fluid-attenuated inversion recovery images (Figure 1B). The mass was well-demarcated, heterogenous, and 2.7 x 1.9 x 2.2 cm in size (width x length x height). Co., Ltd, China], the mass showed strong contrast-enhancement and meningeal enhancement was identified adjacent to the mass (Figure 1C). Cerebrospinal fluid was not obtained because indentation of the cerebellum was observed on MRI and there was a high probability of increased intracranial pressure caused by a large intracranial mass. On day 355 after the initial treatment, a second MRI scan was performed to evaluate tumor size (Figures 1E-H).
18F-fluorodopa (18F-FDOPA) positron emission tomography (PET)/computed tomography (CT) findings in a dog with meningioma. PET/CT scan was performed 119 days after initial chemotherapy. (A) On 18F-FDOPA PET image, increased 18F-FDOPA uptake is shown with a black color, while low uptake is shown with a white color. 18F-FDOPA uptake was remarkable in the lesion (arrows). (B) On PET/CT fusion image, increased 18F-FDOPA uptake appeared to be yellow, while low uptake appeared black to red. (C) A contrast-enhanced CT image shows an intense enhancement of the mass. (D) Bone window CT after contrast medium injection (window width of 2,000 Hounsfield units, window level of 500 Hounsfield units) revealed cranial bone lysis around the tumor (arrowhead).
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On visual evaluation of the PET images, there was marked 18F-FDOPA uptake in the tumor and peritumoral lesion (Figure 2A). The mean and maximal SUV of the lesion were 2.61 and 3.72, respectively; the tumor region showed the mean SUV 2.57 and maximal SUV 3.72, and peritumoral region showed the mean SUV 2.66 and maximal SUV 3.69 (Figure 2B). On post-contrast CT images (Figure 2C), the size of the contrast-enhanced lesion was 2.9 x 2.2 x 2.4 cm (width x length x height), and it was smaller than the hypermetabolic 18F-FDOPA lesion (3.5 x 2.2 x 3.3 cm; width x length x height), with an SUV of >1.91, corresponding to maximal SUV of the normal brain area of the dog. CT scan increased to 7.4% compared with that on the first MRI scan. CT imaging in a bone window (window width, 2,000 Hounsfield units; window level, 500 Hounsfield units) revealed cranial bone lysis around the tumor (Figure 2D).
Histopathology and immunohistochemical evaluation of a meningioma in a dog. (A) Normal brain tissue was compressed by an encapsulated neoplastic mass (asterisk). Hematoxylin and eosin; x6 magnification; bar = 5 mm. (B) Syncytial growth of round to oval meningothelial cells consisting solid sheet and meningeal whorls (arrow). Nuclei contain a clear space with prominent nucleoli (arrowhead). Hematoxylin and eosin; x200 magnification; bar = 100 mum. (C) A Ki67 positive cell (arrowhead) can be observed. Hematoxylin counterstain; x400 magnification; bar = 50 mum. (D) L-type amino acid transporter 1 stain showing strongly diffuse positive staining. Hematoxylin counterstain; x100 magnification; bar = 200 mum.
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Histopathological examination revealed that the normal brain tissue was compressed by an encapsulated neoplastic mass (Figure 3A). The nuclei contained clear spaces with prominent nucleoli (Figure 3B). Neoplastic cells were positive for Ki-67 (Figure 3C) and negative for p53. LAT1 IHC staining showed strong, diffuse positive staining (Figure 3D).