Giant Bone Island of the Tibia in a Child
Giant bone islands have been previously diagnosed only in adults. A symptomatic giant bone island of the tibial diaphysis in a 10-year-old boy is presented in this case report. Imaging investigation included plain radiographs, scintigraphy, computed tomography, and magnetic resonance imaging. Although the findings suggested a giant bone island, the appearance of several atypical imaging features necessitated an open biopsy. Histology confirmed the diagnosis of a giant bone island. Its length, which exceeded 10.8 cm, is the longest reported in the literature. No additional surgical intervention was required. The clinical symptoms and signs, as well as the radiographic appearance of the lesion, were not changed after 15-year follow-up.
The differential diagnosis of a giant bone island includes a variety of benign tumors and tumor-like lesions, as well as malignant bone lesions.2,4,23,28,30,31 In the patient presented in this report, the diagnosis of an atypical sclerotic presentation of a nonossifying fibroma or healing stage of this lesion could be consistent with some of the CT findings, including the eccentric origin from the cortex associated with medial cortical thickening, the anterolateral cortical thinning, and the soft-tissue attenuation of cortical areas. In addition, unifocal osteofibrous dysplasia may also present with a long intracortical diaphyseal lucency within an area of marked cortical sclerosis and cause a bowing deformity. Both diagnoses were excluded, since no fibrous stroma was evident on the histologic examination of the lesion. A large or giant long-bone osteoma would be associated with the outer cortical margin of bone but would not involve the intramedullary space. The scintigraphically increased uptake of radioisotope, as well as the CT and MRI findings, were not consistent with the diagnosis of osteoid osteoma, osteoblastoma, or osteomyelitis. Although most imaging findings were consistent with a benign lesion, and contrast-enhanced MRI showed no increased vascularity, anterior cortical disruption necessitated a bone biopsy to rule out any potential malignancy.
The histopathology in association with the clinical and imaging findings indicated the diagnosis of a giant bone island. The increased proportion of maturing woven bone over lamellar bone indicated an active remodeling lesion that could be related to the patient’s age, since the clinical and radiographic features of the lesion were not changed after 15-year follow-up.
Conclusion
This is the first giant bone island diagnosed in a patient before puberty. Its greatest length was 10.8 cm, which is the longest reported in the literature. The imaging appearance included several atypical features that are very rare or have not been reported. Microscopic features indicated less mature lamellar bone and a prominent proportion of maturing woven bone. The clinical and the radiographic appearance of the lesion were not changed after 15-year follow-up.
