Fibrous Dysplasia Mimicking Bone Metastasis on Both Bone Scintigraphy and (18)F-FDG PET-CT: Diagnostic Dilemma in a Patient with Breast Cancer.

Abstract

Bone is the most common distant site to which breast cancer metastasizes [1]. Commonly used imaging modalities for imaging bone metastasis are bone scintigraphy, plain radiography, computed tomography (CT), magnetic resonance imaging (MRI), and positron emission tomography (PET) [1]. Although bone scintigraphy has high sensitivity for detecting bone metastasis, its specificity is low [2]. This is because of the fact that bone scintigraphy images secondary changes in bone rather than just tumor cells. 18F-fluorodeoxyglucose (18F-FDG) PET-CT, on the other hand, directly images the tumor cells’ glucose metabolism [3]. Unfortunately, similar to bone scintigraphy, benign bone conditions can also show increased 18F-FDG uptake on PET-CT, and PET-positive asymptomatic fibrous dysplasia can be misinterpreted as a metastasis [4]. Fibrous dysplasia of bone has wide skeletal distribution, with variability of 18F-FDG uptake and CT appearance [5, 6]. It is therefore important to recognize the characteristics of this skeletal dysplasia, to allow differentiation from skeletal metastasis [6, 7]. Bone lesions with 18F-FDG uptake need to be carefully interpreted when evaluating patients with known malignancy [8]. In doubtful cases, fibrous dysplasia should be given as a differential diagnosis and histopathological diagnosis may be warranted, as highlighted in the present case (Fig. 1). Fig. 1 A 62-year-old woman had undergone modified radical mastectomy, followed by chemotherapy, radiotherapy, and tamoxifen for medullary carcinoma of the left breast. She developed vague discomfort in the left side of the chest 5 years post surgery. ...