Case Of the Month

Monostotic Aggressive Osteolytic Lesion in an 11-Year-Old MN Yorkshire Terrier: Our Case Of the Month August 2018

An 11-year-old MN Yorkshire Terrier presented for a second opinion for a 4-week history of back pain; an L2 lesion is suspected. Previous treatments were Gabapentin and Tramadol, but the patient showed no improvement. The patient was still very painful, reluctant to move, and baring teeth when owner tried to pick him up. The area of L2 appeared normal on radiographs. CBC was WNL, blood chemistry found an Alk. Phos. of 187 and a PSA lipase of 528. Urinalysis showed 2+ protein. A left medial liver nodule, likely lipogranuloma or benign lesion with minor renal mineralization was seen on ultrasound. The sonographic findings were not contributing to this patient’s pain and there was no evidence of visceral disease that could be contributing to the clinical signs. A CT of the spine with contrast was strongly recommended given the patient’s symptoms.

DX

Monostotic aggressive osteolytic lesion of the L2 vertebra with severe extradural compressive myelopathy.

Outcome

The CT findings are compatible with a primary bone tumor until proven otherwise. Most likely differential diagnoses are osteosarcoma, chondrosarcoma, hemangiosarcoma, fibrosarcoma, or other. The possibility of metastasis of another primary tumor cannot be ruled out entirely. However, in the portions of the thorax and abdomen imaged, no evidence of another primary tumor was found. Unfortunately, the lesion is not resectable. Oncologist consult to discuss palliative tumor irradiation or chemotherapy could be considered. However, the long-term prognosis is poor.

Image Interpretation

An aggressive osteolytic lesion of L2 vertebral body is noted occupying two thirds of the vertebral body. The dorsal cortex of the vertebral body of L2 is lost. There is a contrast enhancing soft tissue component of the lesion causing an extradural mass effect on the spinal cord from the ventral and right ventrolateral aspect. The soft tissue component of the mass occupies approximately 70% of the vertebral canal cross sectional area at maximum and causes deviation and severe compression of the spinal cord at the same level.