Metastatic Adenocarcinoma of Unknown Primary Origin Presenting with Severe Lumbar Neuropathic Pain in a Dog

An eleven year-old, male, beagle was presented with a two-month history of progressive stiff gait and spinal hyperalgesia. On the basis of clinical and magnetic resonance images features, an extensive bilateral paraspinal myopathy was diagnosed. Two weeks later, the dog was euthanized due to the worsening of pain. At post-mortem examination, multiple nodules of variable size were detected along the lumbar paraspinal musculature and the diaphragm pillars. Histologically, nodules were composed by fibroconnectival proliferation arranged around cores of atypical neoplastic cells which were positive for cytokeratine 19, demonstrating a glandular origin. A primary lesion was not found. Here we report an atypical case of adenocarcinoma of unknown primary origin metastasizing to the lumbar muscles and presenting with severe neuropathic pain.