Canine multilobular tumour of the bone arising in non-cranial sites: three cases

The multilobular tumour of bone (MTB) is a relatively uncommon tumour. Its biological behaviour may range from benign to malignant. MTB typically affects the canine skull; MTBs arising in non-cranial sites are exceedingly rare.(1) Here we present a series of three such cases, including two tumours arising in non-cranial skeletal (spinal and pelvic) and an extraskeletal one (muscle). Methods and results. The first tumour reported concerned the medial aspect of the left thigh of an eight-year-old female Cocker Spaniel that was presented with a history of acute lameness. The second tumour reported arose on the body of the first lumbar vertebra of a 10-year-old male Labrador, while the third concerned the right tuber ischii region of a 13-year-old female Corgi. Clinical signs varied depending on location. All animals were euthanized upon the owners’ request. metastases were observed on necropsy. In the first case, a large tough white tumour replacing the heads of the vastus medialis and rectus femoris muscles was evident; no local involvement of bone or joint was observed. Histologically, the tumours varied widely but were all characterized by the dominant presence of multiple osteoid-containing lobules that were separated, to a varying degree, by fibrous septae, a feature typical of MTB. The spinal tumour also contained myxoid-like material and had an atypical morphology. MTB may arise in non-cranial and extraskeletal sites.and should be included in the differential diagnosis of osseous tumours arising in such sites.