The aetiology and distinguishing features of solitary spinal hot spots on planar bone scans

To determine the aetiology of solitary spinal hot spots on planar bone scans and to determine which radiographic and scintigraphic features aid in distinguishing benign from malignant lesions.

81 bone scans showing a solitary hot spot in the spine were identified. Aetiology was determined in 73 based on imaging and clinical findings, including clinical follow-up. The location of the hot spot was classified as paravertebral (related to the lateral spinal margin), panvertebral (diffuse uptake confined within a vertebra), hemivertebral (uptake confined between the midline and lateral spinal margin) or complex (all others).

The aetiology of the spinal hot spot was benign in 55 patients and malignant in 18. The latter all belonged to the subgroup of 42 patients with a known malignancy. Only eight of the 18 malignant cases had suggestive plain radiographic findings. There was no significant relationship between aetiology and age. The spinal level of the hot spot was cervical in three (all benign), thoracic in 16 (eight benign) and lumbar in 54 (44 benign). The hot spot was paravertebral in 21 (all benign), panvertebral in 24 (20 benign), hemivertebral in 13 (10 benign) and complex in 15 (only four benign).

Most (75%) solitary spinal hot spots are benign, and even in patients with known malignancy just over half (57%) are benign. Malignant lesions are often (56%) radiographically occult. Thoracic or complex hot spots are more likely to be malignant while paravertebral hot spots are characteristically benign. These features may be helpful in distinguishing benign and malignant lesions in patients with a known malignancy and unremarkable radiographs. Other scintigraphic features are unhelpful in distinguishing benign from malignant lesions.