Malignant versus nonmalignant bone disease

Diagnosis of bone lesions other than fractures is difficult from radiograph s alone because mixed patterns of lysis and bone proliferation are frequent ly observed. It is important to evaluate whether the lesion is single (mono stotic) or involving multiple bones (polyostotic). Correlation of additiona l information such as the patient signalment, sex, geographic habitat histo ry, clinical findings, and prior therapy is useful to help establish the mo st accurate differential diagnosis. The presence of intramedullary lesions with expansile destructive pattern in the metaphyseal region of a middle-ag ed, large-breed dog is supportive for a diagnosis of a primary bone tumor o r an aggressive mycotic osteomyelitis. Serial radiographic studies can be p erformed to evaluate progression. Rapid bone change tends to occur with neo plasia, whereas slower progression can occur with osteomyelitis. The locati on of change to the vertebrae, such as spondylitis and diskospondylitis, of ten helps in the understanding of the underlying disease process. Additiona l diagnostic procedures, such as biopsies with appropriate lesion sampling and evaluation of serum for fungal titers, should be considered to establis h the diagnosis.