The aetiology of solitary hot spots in the ribs on planar bone scans.

The aim of this study was to determine the aetiology of solitary hot spots in the ribs found at bone scintigraphy in patients with known extraskeletal malignancy. A group of 34 patients whose bone scans showed a solitary hot spot in a rib were identified retrospectively over a 4-year period. They all had a known extraskeletal malignancy. Aetiology of the rib hot spot was established in 26 patients based on a review of clinical features, radiographic findings and clinical follow-up. In eight cases it remained indeterminate. In 14 (41%) cases, the rib lesion was malignant in origin, 9 were due to metastasis and 5 due to direct spread from intrapulmonary malignancy. In 12 (35%) cases, it was benign. In the remaining 8 (24%) cases, the aetiology was indeterminate. In the subgroup of 14 hot spots confined to the anterior rib end, 5 (36%) were due to malignancy, 4 (28%) were benign and 5 (36%) were indeterminate. We conclude that solitary hot spots in the ribs of patients with known extraskeletal malignancy undergoing bone scintigraphy are frequently (41%) malignant in origin. This also applies when the hot spot is in the anterior rib end (36% malignant). Thus, such hot spots are far more sinister than previously reported and require careful clinical and radiographic evaluation.