MRI Features of Solitary Vertebral Masses in Dogs: 20 Cases (2010-2019)

A "gullwing sign" on magnetic resonance imaging of extradural spinal tumors in dogs and cats allows prioritization of round cell neoplasia

Extradural neoplasms are the most common spinal tumors in small animals. A bilobed appearance of ventral extradural spinal lesions ("gullwing sign") on MRI has been described with various conditions. The objective of this retrospective study was to determine if a "gullwing sign" is more common with certain types of extradural tumors. MRI studies of dogs and cats with extradural spinal neoplasms were reviewed for the presence of a "gullwing sign". Statistical analysis was performed to evaluate a possible relationship between tumor class and the presence of a "gullwing sign". Sixty-six cases were included (5 epithelial, 31 mesenchymal, 4 neuroendocrine, and 26 round cell tumors). A "gullwing sign" was identified in 12 of 66 cases (18.2%) and was significantly more common with round cell neoplasia than other tumor types (P < .001; OR = 28.6, 95% CI [3.4, 241.1]). This information may aid radiologists in prioritizing differential diagnoses for extradural tumors in small animals.

Updates in Osteosarcoma

Clinical care of osteosarcoma (OSA) in dogs has seen little change during the past 2 decades, relying on amputation and platinum-based chemotherapy for pain control and survival. Recent advancements offer hope for improved outcomes. Genomic research reveals shared genetic abnormalities between canine and human OSA. Multidimensional imaging provides valuable staging and prognostic information. Limb-sparing approaches including stereotactic body radiation therapy are routine. Ablative therapies such as microwave ablation and histotripsy show promise. Immunotherapy including cell therapy and immune checkpoint inhibition are available. Radiopharmaceuticals are tuned to target OSA cells directly. These innovations may enhance treatment and prognosis for dogs with OSA.

Cranial and vertebral osteosarcoma commonly has T2 signal heterogeneity, contrast enhancement, and osteolysis on MRI: A case series of 35 dogs

Magnetic resonance imaging (MRI) is commonly used to evaluate the central nervous system (CNS) in dogs; however, published studies describing the MRI appearance of cranial and vertebral osteosarcoma are scarce. In this multicenter, retrospective, case series study, MRI studies of 35 dogs with cranial or vertebral osteosarcoma were prospectively scored by consensus of two veterinary radiologists. Recorded characteristics were location, signal intensity (compared to gray matter), homogeneity, contrast enhancement, margin delineation, local invasion, osteolysis, osteosclerosis, zone of transition, periosteal proliferation, pathological fracture, meningeal/CNS involvement, and presence of metastatic disease. Locations included the parietal bone (n = 1), occipital bone (n = 2), or cervical (n = 5), thoracic (n = 17), lumbar (n = 7), or sacral vertebrae (n = 3). Common features included signal heterogeneity in T2-weighted (T2W) images (n = 35), contrast enhancement (in all 34 dogs with postcontrast MRI), osteolysis (n = 34), compression of the CNS or cauda equina (n = 33), an associated soft tissue mass (n = 33), a long zone of transition (n = 30), osteosclerosis (n = 28), signal isointensity to normal-appearing gray matter in T1-weighted images (T1W, n = 26), and T2W hyperintensity of adjacent brain or spinal cord (n = 23). Other findings included periosteal proliferation (n = 18), meningeal contrast enhancement (n = 17), T1W and T2W hypointense foci in the soft tissue mass (n = 14), invasion into adjacent bones (n = 10), pathological vertebral fractures (n = 7), regional lymphadenopathy (n = 6), skip metastases (n = 2), lung nodule (n = 1), diaphragmatic nodule (n = 1), and brain invasion (n = 1). Contrast enhancement was typically strong and heterogeneous. Magnetic resonance imaging features of cranial and vertebral osteosarcoma were analogous to those previously reported for other imaging modalities. Osteosarcoma should be a differential diagnosis for compressive, contrast-enhancing, osteolytic lesions of the cranium or vertebrae.