The purpose of this study was to describe the clinical and imaging features of metastatic bone tumors with sunburst periosteal reaction and to define the characteristic findings which would be helpful for differentiating metastatic bone tumors from primary malignant bone tumors.

The authors retrospectively reviewed the cases of nine patients with pathologically confirmed metastatic bone tumors with sunburst periosteal reaction, for which imaging studies (plain radiographs [n=9], radioisotope [RI] scans [n=4], magnetic resonance [MR] images [n=6], and computed tomographic [CT] scans [n=4]) were performed. The imaging studies of each lesion were analyzed by two musculoskeletal radiologists focusing on the metastatic site, patterns of bone response, signal intensity characteristics and pattern of contrast enhancement on MR. The clinical records of the patients were reviewed with regard to the age and sex of the subjects, the clinical presentation, and the origin of the primary tumors.

The cases consisted of six men and three women, whose mean age was 62 years (age range, 50-88 years). The primary tumors were adenocarcinoma of the stomach [n=4], adenocarcinoma of the lung [n=2], adenocarcinoma of the prostate [n=1], hepatocellular carcinoma of the liver [n=1], and adenocarcinoma of unknown origin [n=1]. The sites of metastatic involvement exhibiting sunburst periosteal reaction were the scapula [n=2], proximal humerus [n=2], rib [n=1], iliac bone [n=1], tibia [n=1], spine [n=1], and proximal phalanx [n=1]. In all patients, the imaging findings showed osteolytic [n=3] or osteoblastic [n=6] lesions with sunburst periosteal reaction. In six cases, the lesions were iso-intense on the T1-weighted images and heterogeneously hyperintense on the T2-weighted images. The gadolinium-enhanced T1-weighted images showed a nearly homogenous enhancement of the lesions without any central necrotic portion.

Although metastatic bone tumor exhibiting sunburst periosteal reaction is rare, it should be included along with primary malignant bone tumors in the differential diagnosis of bone lesions with sunburst periosteal reaction, especially in older patients with or without a known primary malignancy.