Imaging and pathological findings of intramedullary inflammatory pseudotumour in a miniature dachshund: a case report

Abstract

Background: Inflammatory pseudotumours (IPTs) are distinctive lesions consisting of myofibroblastic spindle cells and a variety of inflammatory cells. The aetiology of IPTs is unknown. Reports of IPTs in veterinary medicine have been scarse. Moreover, only one case of intradural extramedullary IPT has been previously reported. In this report, we introduce the first known case of canine IPT, which occurred in the parenchyma of the spinal cord.

Case presentation: A 10-year-old female Miniature Dachshund presented with a 2-month-long history of progressively worsening ataxia and tetraparesis. Neurological examination was consistent with a lesion involving the cervical spinal cord. Magnetic resonance imaging revealed an intradural space-occupying lesion in the region of the fourth cervical vertebra. Dorsal laminectomy and resection of the mass were performed. Histopathological examination revealed the proliferation of immature spindle cells (fibroblasts/myofibroblasts and glial cells) and a highly cellular mixture of neutrophils, macrophages and lymphocytic cells. The mass was located in the parenchyma of the spinal cord and was diagnosed as an IPT occurring in the parenchyma of the spinal cord. No causative pathogen was detected. The dog's symptoms improved, during the first month after surgery. However, neurological symptoms, such as laboured breathing and dysuria, subsequently worsened and the dog died 42 days after surgery.

Conclusions: The present study describes a canine case of IPT occurring in the parenchyma of the spinal cord. The diagnosis and determination of the site of the mass was difficult solely based on preoperative imaging in the present case. The outcome of this case was poorer than that observed in cases of canine extramedullary IPT and human intramedullary IPT, in which the patients exhibited recovery. The prognosis after surgical resection cannot be decided from the present case alone. However, patients should be monitored for potential serious complications and recurrence.

Keywords: Canine tumour; Paresis; Pseudotumour; Spinal cord parenchyma.

Fig. 1

Magnetic resonance imaging of the intradural mass lesion. Sagittal T2-weighted images reveal a mass in the dorsal spinal cord at the fourth cervical (C4) level (yellow arrow) and a large hyperintense lesion from C2 to C6 (yellow arrowheads) (a). The mass is isointense (yellow arrow), and the area around the mass is isointense (b) on T1-weighted images. The mass is hypo- to isointense (yellow arrow), and the area around the mass is hyperintense on fluid attenuated inversion recovery imaging (yellow arrowheads) (c). The mass is homogenously enhanced (yellow arrow) after contrast administration and shows a dural tail sign (yellow arrow head) on T1-weighted imaging (d). The mass (yellow arrows) is spherical and homogenously enhanced after contrast administration on T1-weighted transverse imaging (e)

Fig. 2

Intraoperative image of the lesion. The arrowhead indicated the incised dura mater. The dura mater covering the mass is thinner than normal dura mater, and the mass is located within the dura mater. The mass is red, indicating angiogenesis. The boundary between the mass and normal spinal cord tissue is unclear (arrow) (a). Intraoperative ultrasonic inspection shows that the mass is homogenous and hyperintense relative to the normal spinal cord; the boundary between the mass and normal spinal cord can be confirmed (b, circle)

Fig. 3

Histopathological images of the inflammatory pseudotumour. These images reveal a highly cellular mixture of neutrophils, macrophages, and lymphocytes (a; inset shows the nuclei of macrophages and neutrophils) and numerous chromatin-rich, spindle-shaped cells (b, elongated nucleus of activated glial cells). In addition, immunohistochemically- labelled S-100 (nerve cell marker)- and GFAP (astrocytic cell marker)-positive cells are observed within the mass (c and d). The pia mater (arrowheads in C and D) is observed on the surface of the mass. Scale bars are 100 μm in A and B and 50 μm in c and d

Fig. 4

Immunohistological images of immune cells and a cell proliferation marker in mass tissue. Large amounts of Iba-1 (macrophage marker)-positive cells are observed (a); CD3 (T lymphocyte marker)- and CD79α (B lymphocyte marker)-positive cells are present (b and c), as are Ki-67 (cell proliferation marker)-positive cells (d). Scale bars are 100 μm