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A lumbar extradural lymphoma compressing the spinal cord was identified on contrast enhanced computed tomography (CT) and magnetic resonance imaging (MRI) images in a 4-year-old Bordeaux dog presented with posterior paresis. A significant paravertebral extension was only clearly defined on contrast MRI images; therefore, MRI was more useful than CT in imaging of spinal extradural lymphoma in this dog.
Imagerie comparative d’un lymphome extradural spinal chez un chien Bordeaux. Un lymphome extradural lombaire comprimant la moelle épinière a été identifié par une tomodensitométrie rehaussée par un agent de contraste et par des images par résonance magnétique (IRM) chez un chien Bordeaux âgé de 4 ans présenté avec une parésie postérieure. Une extension paravertébrale significative a seulement été clairement définie sur des images d’IRM de contraste; par conséquent, l’IRM a été plus utile que la tomodensitométrie pour l’imagerie d’un lymphome extrudural spinal chez ce chien.
(Traduit par Isabelle Vallières)
A 4-year-old, 53-kg, castrated male, Bordeaux dog was referred to the Department of Clinical Sciences of Companion Animals of Utrecht University with a 4-day history of right hind limb lameness, posterior paresis, and loss of control of urination and defecation.
At presentation, the dog was paretic in both hind limbs and had proprioceptive deficits. Spinal reflexes (patellar reflex, tibialis anterior reflex, and withdrawal reflex) were normal and conscious pain perception was present. Palpation of the thoracolumbar vertebral column and extension of the low back evoked a pain response. Clinical and neurological examination localized the spinal lesion between the 3rd thoracic and 3rd lumbar cord segments. The differential diagnosis included neoplasia and less likely a degenerative cause (such as intervertebral disc degeneration), infection or trauma.
The dog was anesthetised and ventrodorsal and lateral radiographs of the thoracic, lumbar, and sacral vertebral column were obtained. A minor angular deformation and malalignment of the vertebral column was noted at the level of L3–L4 (Figure 1). Widening of the intervertebral disc space on the left side and narrowing on the right side with smooth and well-defined new bone formation at the level of the left synovial articulation were present at this level. A less prominent widening and narrowing of the right and left side, respectively, were noted at the intervertebral disc space of L4–L5.
Computed tomography (CT) of the thoracolumbar vertebral column was performed with the anesthetised dog in ventral recumbancy. Scans were obtained with a slice thickness of 2 mm, using 120 kV and 320 mA, both before and 2 and 15 min after the administration of an intravenous (IV) bolus of 60 mL iobitrol contrast medium (Xenetix 350, 350 mg I/mL; Guerbet, Aulnay, Belgium). An extradural mass at the right and dorsal side of the vertebral canal, with compression and displacement of the spinal cord to the left and ventral at the level of L2 to L4, was present in the CT images. A partial mineralization of the dura mater was noted at the cranial and caudal side of the lesion. The soft tissue mass extended to the intervertebral foramina of L2–3 and L3–4. Contrast enhancement was progressive over time but remained minimal and an ill-defined soft tissue mass was noted on the right lateral side of L3, slightly displacing the m. longissimus and the m. iliocostalis laterally (Figure 2A). Malformation of the left synovial articulation and adjacent lamina of L3 and L4 due to new bone formation with subsequent malalignment (visible with dorsal plane reconstruction) of the vertebral column at this level was noted as in the radiographs.
Subsequently, magnetic resonance imaging (MRI) was performed on the lumbar vertebral column extending from L1 to L4. Transverse T1-weighted images (TR 624, TE 26, slice thickness 4 mm, interslice space 2 mm) before and after IV injection of 16 mL gadoteric acid contrast medium (Dotarem, 0.5 mmol/mL, Guerbet, Gorinchem, The Netherlands) were obtained as well as pre-contrast sagittal T2-weighted images (TR 5000, TE 102, contiguous slice thickness 3 mm). The mass lesion had a slightly heterogeneous intensity and was slightly hyper-intense to the lumbar musculature and spinal cord on pre-contrast T1-weighted images and on T2-weighted images (Figure 3). A clear contrast enhancement of the entire lesion was visible in the post-contrast T1-weighted images; this was well-defined and sharply marginated (Figure 2B). The lesion was visible for 5.5 cm in the vertebral canal from mid L2 to the cranial side of L4 and was clearly compressing and displacing the spinal cord ventrally and to the left. Via the right 1st and 2nd lumbar intervertebral foramina the lesion extended laterally to a larger right paravertebral area. This part of the lesion was noticeable for 6.5 cm, expanding from mid L2 to mid L4. The thickest part of the paravertebral region measured 2.7 × 3.2 cm and displaced the m. iliocostalis and m. longissimus laterally. There was a vague demarcation between muscular tissue and the lesion, suggestive of local invasion of the surrounding tissues. There was no evidence of bony involvement on any of the 3 imaging modalities. The CT and MRI findings are compatible with a diffuse neoplastic process, such as a soft tissue tumor or, less likely, a tumor derived from the spinal cord or nerve roots, such as a nerve sheath tumor.
The dog was euthanized on the owners’ request. Post-mortem examination was performed and included macroscopic and microscopic evaluation. Tissue samples taken for histopathology were fixed in 4% neutral-buffered formaldehyde solution. After fixation, samples were trimmed and paraffin-embedded. Subsequently 3- to 5-μm sections were cut and routinely stained with hematoxylin and eosin. Routine immunohistochemical stains for CD3 and CD79 alpha were performed to determine T- or B-cell origin. The diagnosis of neoplasia was based on criteria published in the World Health Organisation International Classification of Tumours of Domestic Animals series. Macroscopically, a poorly circumscribed non-encapsulated pale neoplastic mass was present in the right m. longissimus dorsi from mid L2 — end L3 vertebrae. The peripheral nerve of the 2nd lumbar intervertebral foramen was thickened due to a similar pale amorphous tissue mass, which expanded extradurally approximately 6 cm in length and approximately 1 cm in width from mid L2 to mid L4. Compression of the spinal cord by the neoplasm was evident; however, no bone lesions were detected. No other neoplasias and no enlarged lymph nodes were encountered.
With histopathology, an invasive neoplasm composed of sheets of large rounded polyhedral mononuclear tumor cells with marked anisocytosis and anisokaryosis and abundant mitotic figures was identified (4 to 5 per averaged field of 400×). The tumor displayed mild invasive growth of both the peripheral nerve (2nd foramen) and dura mater, and severe invasion of the surrounding muscle tissue and fibrous connective tissues. The histopathological findings are consistent with a diagnosis of an extra-dural malignant T-cell lymphoma with spinal cord compression.
The present report describes the findings of a spinal extradural malignant lymphoma in and adjacent to the lumbar vertebral column causing acute posterior paresis. Malignant lymphoma, also called lymphosarcoma, resembles non-Hodgkin’s disease in humans (1). Many different anatomic forms have been described such as multicentric, alimentary, renal, urogenital, cutaneous, mediastinal, cardiac osseous, and nervous system (2–8). Lymphoma has been found in and adjacent to the spinal cord and cranium as a primary tumor or as a secondary metastatic neoplastic lesion, causing clinical signs associated with the nervous system (7,9–14). The use of imaging modalities such as radiography and ultrasound in the evaluation and staging of the multicentric thoracic and abdominal lymphoma and CT, MRI, and scintigraphy of cranial, spinal, and brachial plexus lymphoma has been described (15–22). The development of more sensitive modalities has caused an upward shift in the staging of lymphoma and a standardized method in staging lymphoma is preferable (22).
To the authors’ knowledge, no reports are available in the veterinary literature, which describe both CT and MRI findings of an extradural malignant lymphoma in a dog. This report emphasizes the importance of contrast MR imaging instead of contrast CT imaging of spinal malignant lymphoma. Although the vertebral canal lesion was well-defined on CT images, the true extension and demarcation outside the spinal canal was not clear compared to the MRI findings. This was also described for mesenteric lymphoma (20). The changes at the level of the left synovial articulation of L3–4 were most likely due to old trauma or could represent severe osteoarthrosis and were considered a coincidental finding.
In conclusion, contrast enhancement in MRI was superior to contrast enhancement in CT for spinal extradural lymphoma in this case. CVJ
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