Primary diffuse leptomeningeal gliomatosis in 2 dogs

Abstract

Clinical, neuroimaging, and neuropathological findings of 2 cases of canine primary diffuse leptomeningeal gliomatosis are described. Magnetic resonance imaging and histopathological examination of the brain revealed diffuse leptomeningeal alterations with no parenchymal involvement. These cases share many similarities with the same disease in humans.

Figure 1

Magnetic resonance images (A,B) from Case 1. A — Transverse postcontrast T1-weighted (TE 24 ms; TR 690 ms) image at the level of the medulla oblongata. B — Dorsal postcontrast T1-weighted (TE 24 ms; TR 620 ms) image at the level of the fourth ventricle. Note dilation of the lateral and fourth ventricles (arrows, Figures 1A,1B) and widespread enhancement of the meninges of the medulla oblongata (arrowheads, Figure 1A). C — Irregular and gelatinous leptomeningeal thickening in the rhomboencephalic ventral surface (arrows). The orientation left/right was flipped to facilitate comparison with MRI images.

Figure 2

Histological and immunohistochemical features of Case 1. A — Mesencephalic leptomeningeal mass characterized by round well-defined neoplastic cells, with hyperchromatic nuclei and perinuclear halo [hematoxylin and eosin (H&E)] (×40). B — Olig2-immunoreaction is expressed as a nuclear pattern in about 80% of the neoplastic cells (anti-Olig2 antibody, ABC IHC-method, Carazzi’s counterstain, ×40).

Figure 3

Magnetic resonance images (A,B) for Case 2. A — Transverse postcontrast T1-weighted (TE 24 ms; TR 644 ms) image at the level of diencephalomesencephalic junction. B — Dorsal postcontrast T1-weighted (TE 24 ms; TR 620 ms) image at the level of the temporal area. There are multifocal contrast enhancing lesions (arrows) involving mostly the meninges at the level of the transition between diencephalon and mesencephalon (Figure 2A) and at the level of mesencephalon, third ventricle, interthalamic adhesion, and right prosencephalon (Figure 2B). C — A brownish mass dramatically disfigures the diencephalomesencephalic profile (arrows). The orientation left/right was flipped to facilitate comparison with MRI images.

Figure 4

Histological and immunohistochemical features of Case 2. A — Neoplastic cells infiltrating brain leptomeninges arranged in a storiform pattern (H&E, ×40). B — Neoplastic fusiform cells infiltrating brain leptomeninges have long GFAP-positive cytoplasmic processes (anti-GFAP antibody, ABC IHC-method, Carazzi’s counterstain, ×40).