PET/CT Follow-Up in Nonossifying Fibroma

Abstract

2Present address: Division of Nuclear Medicine, Stanford University Medical Center, 300 Pasteur Dr., Rm. H-0101, Stanford, CA 94305. Address correspondence to A. Iagaru (aiagaru@stanford.edu). onossifying fibroma is a common benign finding encountered in the practice of radiology. Nonossifying fibromas are well-circumscribed, solitary fibrous proliferations. The lesions are found mostly in children, with 75% occurring in the second decade. Lesions are more common in males than in females, and may occur in as many as 35% of all children. The process is nonneoplastic and occurs in the juxtaepiphyseal region of the long bones. The most common site is the femur, followed by the tibia [1]. Clinically, nonossifying fibromas are asymptomatic and are usually discovered as an incidental finding on a radiograph. Occasionally, a larger lesion presents as a pathologic fracture. Nonossifying fibromas normally regress spontaneously. The only definite indication to treat nonossifying fibromas is a pathologic fracture [2]. On unenhanced radiographs, a nonossifying fibroma appears as an eccentric radiolucent lesion with thinned cortex, which can have a multilocular appearance and, often, a sclerotic margin. With time, radiographs will show increasing marginal sclerosis followed by progressive ossification of the lesion extending from its diaphyseal aspect. If a CT or MRI is obtained for nonossifying fibroma, the cortex will often appear interrupted, which can be interpreted as cortical destruction [3]. However, this is secondary to cortical replacement by benign fibrous tissue. The CT will show an eccentric lesion with central radiolucency. The MRI may show variable signal intensity and septations, depending on the lesion’s stage of healing [4]. On a technetium 99m (99mTc) methylene diphosphonate bone scan, the nonossifying fibroma will show minimal or no increased uptake of the radiopharmaceutical, unless traumatized [5]. To our knowledge, the appearance of nonossifying fibroma on 18F-FDG PET and the possibility of following up regression of nonossifying fibroma with PET have not been previously reported.