Presumptive malignant nerve sheath tumour affecting the cauda equina and caudal nerves of a dog

A 13-year-old, male, entire cocker spaniel was presented with a history of progressive discomfort during defecation. The referring veterinary surgeon suspected anal sacculitis and treated accordingly; however, this was unsuccessful, and the dog was referred for further investigations. Examination revealed marked resentment to manipulation of the tail but was otherwise unremarkable. Radiographs revealed lytic lesions in the first three caudal vertebrae, and MRI of the lumbosacral and first caudal nerves revealed severe enlargement of the caudal nerves within the vertebral canal with extension into the right ventral branches. These findings were highly suggestive of a nerve sheath tumour. Histological and immunohistochemical analysis of sampled tissues supported the suspected diagnosis. The dog was euthanised based on the guarded prognosis and perceived poor quality of life. This report describes an infrequent location for nerve sheath tumour with tail pain and discomfort during defecation as the only clinical manifestations.