Can you name this neoplasm?

Frontiers 2021

Mylène Auger, Silke Hecht, Cary M. Springer

Background
Extradural spinal neoplasia is the most prevalent form of spinal tumors in dogs and cats, often leading to spinal cord compression and dysfunction. This retrospective study aims to describe the magnetic resonance imaging (MRI) characteristics of extradural spinal neoplasia in dogs and cats to distinguish tumor classes and types.

Methods
The study reviewed MRI scans and associated medical data for 60 dogs and 7 cats diagnosed with extradural spinal neoplasia from April 2008 to April 2020. Tumors were classified by type, and MRI characteristics such as lesion location, size, contrast enhancement, and invasiveness were analyzed. Statistical analyses were performed to identify features predictive of specific tumor classes.

Results
Canine Findings:
-Tumor Classes: Mesenchymal tumors (48%) were most common, followed by round cell tumors (35%), epithelial tumors (12%), neuroendocrine tumors (2%), and benign tumors (3%).


MRI Features:
-Round cell tumors showed cortical sparing, homogeneous contrast enhancement, and lesions centered on bone.
-Mesenchymal tumors displayed cortical lysis, heterogeneous enhancement, and lesions centered on paraspinal soft tissues.
-Epithelial tumors commonly had cavitary components and were polyostotic.


Specific Tumors: Lymphoma and multiple myeloma were common round cell tumors, while undifferentiated sarcoma and osteosarcoma dominated mesenchymal types.


Feline Findings:
-Lymphoma was the predominant tumor type (71%), often presenting as epidural masses with or without bone involvement.


Limitations
The study was limited by its retrospective nature and small sample size for cats and certain tumor types, reducing statistical power. Furthermore, some MRI findings overlap between tumor classes, complicating differentiation.

Conclusions
MRI features such as cortical involvement, contrast enhancement patterns, and lesion location can help prioritize differential diagnoses of extradural spinal neoplasia. However, definitive diagnosis relies on histopathology or cytology. These findings enhance diagnostic precision and guide treatment planning for spinal tumors in dogs and cats.

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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