Extradural spinal tumours: Round cell neoplasia respects the cortices!

Front. Vet. Sci., 2021

December 25, 2024

Mylène Auger, Silke Hecht, Cary M. Springer

Background
This study explores the magnetic resonance imaging (MRI) features of extradural spinal neoplasia in cats and dogs, aiming to identify distinguishing characteristics across tumor types. Extradural tumors, the most common spinal neoplasms in these species, include mesenchymal tumors, round cell tumors, and epithelial tumors, which vary in clinical presentation and prognosis. Understanding these features aids in differential diagnosis and treatment planning.

Methods
The study retrospectively reviewed spinal MRI scans from 60 dogs and 7 cats conducted between April 2008 and April 2020. Diagnoses were confirmed via cytology, histopathology, or published diagnostic criteria. MRI evaluations included T1/T2 signal intensities, lesion location, centering (bone, epidural, or paraspinal tissues), contrast enhancement patterns, and the presence of cortical lysis or sparing. Statistical analysis assessed the relationships between MRI features and tumor classes.

Results

  • Dogs: Mesenchymal tumors (48%) were the most common, followed by round cell neoplasms (35%) and epithelial tumors (12%). Undifferentiated sarcomas and lymphoma were the predominant subtypes within these categories.

  • Cats: Lymphoma was the most frequent tumor type (71%), followed by mesenchymal and epithelial neoplasms.

  • MRI features that distinguished tumor classes:

  • Mesenchymal tumors: Often exhibited cortical lysis, heterogeneous contrast enhancement, and larger soft tissue masses.

  • Round cell tumors: Frequently showed cortical sparing, preserved vertebral shape, and small homogeneously enhancing masses.

  • Epithelial tumors: Tended to involve paraspinal soft tissues with cortical lysis and heterogeneous enhancement.

  • Logistic regression revealed specific features, such as vertebral shape preservation and lesion centering, were predictive of tumor class (78.2% accuracy).


Limitations
The study's findings are constrained by its retrospective design and small sample size for some tumor classes, limiting generalizability. Additionally, variable MRI protocols and equipment may affect feature detection and analysis.

Conclusions
MRI features provide valuable clues for differentiating tumor classes and prioritizing differential diagnoses in extradural spinal neoplasia. However, definitive diagnosis still relies on tissue sampling. This study supports the utility of imaging in guiding diagnostic and treatment strategies in veterinary practice.

FIGURE 1 | Examples of cortical sparing, cortical lysis, and benign/reactive
bone change. Transverse (A) T1W image and (B) post-contrast T1W image
with fat saturation at the level of the seventh lumbar vertebra in an 8-years-old
male castrated Australian Cattle Dog diagnosed with lymphoma with cortical
sparing of the affected bone. There is homogeneous contrast enhancement of
the medullary cavity without cortical lysis (*) with mild contrast enhancement of
the adjacent paraspinal soft tissues (white arrows) and contrast-enhancing soft
tissue extending into the vertebral canal. Transverse (C) T1W image and (D)
post-contrast T1W image with fat saturation at the level of the sacrum in an
8-years-old male castrated Great Dane diagnosed with osteosarcoma with
extensive cortical lysis of the affected bone. There is a large, ill-defined,
heterogeneously contrast-enhancing mass centered on the sacrum (white
arrowheads) and extending into the vertebral canal and paraspinal soft tissues
(*). (E) Transverse T2W image and (F) dorsal post-contrast T1W image with fat
saturation at the level of the caudal aspect of L7 and L7-S1 intervertebral
foramen in a 4-years-old male castrated domestic shorthair cat diagnosed
with a peripheral nerve sheath tumor with benign/reactive changes of the
affected bone. There is a strongly contrast-enhancing (black arrowheads)
extradural mass following the L7 nerve root (*) causing smooth widening of the
left aspect of the vertebral canal and of the left L7-S1 intervertebral foramen
(white arrows).

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