Preoperative measurement of canine primary bone tumors, using radiography and bone scintigraphy.

Specimens of 20 canine primary bone tumors (18 osteosarcoma, 2 fibrosarcoma) were examined to compare the maximal axial length of gross tumor with the length of the lesion seen on preoperative radiographs and 99mTc methylene diphosphonate bone scintigraphic images. Radiographs defined the length of the tumor to within +/- 10% of the gross measurement for 6 (30%), underestimated it for 12 (60%), and overestimated it for 2 (10%) specimens. Bone scintigraphy defined tumor length within +/- 10% for 8 (40%), underestimated it for 1 (5%), and overestimated it for the remaining 11 (55%) specimens. Use of radiographic evaluation alone could result in underestimation of the diaphyseal extent of a primary bone tumor, with risk of incomplete resection. Bone scan images tend to overestimate tumor length and, therefore, may provide safer resection guidelines.