Case Report: Long-Term Chemotherapy With Hydroxyurea and Prednisolone in a Cat With a Meningioma: Correlation of FDG Uptake and Tumor Grade Assessed by Histopathology and Expression of Ki-67 and p53

Abstract

A 15.5-year-old, neutered, male, domestic shorthair cat was presented with neurologic dysfunctions. At presentation, an obtunded mental status and vestibular ataxia were identified. On neurologic examination, postural reactions were decreased-to-absent in all four limbs, and pupillary light reflexes showed bilaterally delayed results. Magnetic resonance imaging was performed, and a demarcated lesion was identified in the third ventricle. The cat was tentatively diagnosed with a brain tumor, which was suspected to be a meningioma. The cat was treated with hydroxyurea and prednisolone. Mental status was considered more alert, and ataxia improved following treatment. On the 106th day after the commencement of treatment, a ¹⁸F-fluorodeoxyglucose (FDG)-positron emission tomography (PET) scan was performed. On the PET images, a hypermetabolic region was found in the lesion. The average standardized uptake value of FDG was 2.47, and the tumor-to-normal-tissue ratio was 1.25. The cat died 408 days following the commencement of treatment, and a grade 1 meningioma was confirmed by postmortem histopathology. Immunohistochemistry for Ki-67 and p53 was performed. The labeling indices of Ki-67 and p53 were 2.56 and 0%, respectively. This case shows that chemotherapy with hydroxyurea and prednisolone may be considered in the treatment of feline meningiomas. Furthermore, this is the first case describing the application of FDG-PET to visualize a naturally occurring meningioma in a cat.

Keywords: brain tumor; chemotherapy; feline; hydroxyurea; positron emission tomography.

Figure 1

Findings of the first magnetic resonance imaging of a cat with a meningioma. T2-weighted (A,E), fluid-attenuated inversion recovery (FLAIR) (B), T1-weighted (C,F), and post-contrast (D) images were obtained. An oval-shaped mass is identified in the third ventricle, showing mass effects on the rostral cerebellum, brainstem, and occipital cortex. The mass appears hypointense-to-isointense in T1-weighted images (C,F) and isointense-to-hyperintense in T2-weighted (A,E) and FLAIR (B) images. The lesion is heterogeneously enhanced in the post-contrast image (D).

Figure 2

Second magnetic resonance imaging (MRI), ¹⁸F-fluorodeoxyglucose (FDG)-positron emission tomography (PET), and necropsy findings of meningioma in a cat. (A–E) On the second MRI (106 days after the commencement of treatment), the size of the mass appears similar to that measured at the first MRI. (F) On FDG-PET image, high FDG uptake is seen, represented with a black color, while low FDG uptake is represented with a white color. The FDG uptake in the tumor lesion (arrows) is relatively higher than that of the surrounding regions. (G) On PET/computed tomography fusion image, high FDG uptake is represented as yellow color, while low FDG uptake is represented by black to red color. Glucose metabolism in the third ventricle (arrows) is relatively higher than that in the surrounding regions. (H,I) A well-demarcated, oval-shaped mass (arrows) is observed in the third ventricle.

Figure 3

Histopathological and immunohistochemical findings of meningioma in a cat. (A) Extensive concentric whorls (arrows) of polygonal to oblong cells, and spindle shaped cells with interlacing bundles of fibroblast-like cells are observed. Some psammoma bodies (mineralized concretions; arrowheads) are scattered throughout the mass. Hematoxylin and eosin; ×200 magnification; bar = 50 μm. (B) Positive immunoreactivity to Ki-67. Hematoxylin and eosin; ×400 magnification; bar = 50 μm. (C) Negative immunoreactivity to p53. Hematoxylin and eosin; ×400 magnification; bar = 50 μm.