Atypical magnetic resonance imaging findings of a vertebral melanotic melanoma in a dog

Abstract

An 8‐year‐8‐month‐old whippet was investigated by magnetic resonance imaging for acute thoracolumbar discomfort and pelvic limb stiffness, which had progressed to severe ambulatory paraparesis and proprioceptive ataxia of the pelvic limbs in the 24 hours before presentation. An aggressive, extradural T10 vertebral mass‐like lesion was identified, with resultant marked compression of the spinal cord. The lesion was heterogeneously T2‐weighted hyperintense and moderately T1‐weighted hyperintense relative to the adjacent vertebrae and paravertebral musculature. Cytological analysis of the lesion was consistent with a melanotic melanoma, which was confirmed by histopathological analysis and immunohistochemistry. The vertebral column is an uncommon location for either primary or metastatic melanomas in both humans and veterinary species. This lesion was particularly unusual in that its imaging characteristics were not typical for melanotic melanoma. This case report illustrates the unusual anatomical and imaging features of this tumour and outlines the diagnostic considerations pertinent to this case.

Case report: MRI and CT imaging features of a melanocytic tumour affecting a cervical vertebra in an adult dog, and review of differential diagnosis for T1W-hyperintense lesions

“…However, there are reports indicating that this is not always the case. An example of this includes a recent case of an extradural melanoma affecting a thoracic vertebra in a dog, where the lesion was hyperintense on both T1W and T2W images ( 7 ). Similarly, a case of meningeal melanomatosis characterised by T1W hyperintensity and T2W hyperintensity with a few small areas demostrating T2W hypointensity has also been described in the literature ( 8 ).…”