Polyostotic Fibrous Dysplasia Mimicking Multiple Bone Metastases in a Patient with Ductal Carcinoma In Situ

Whole-body bone scans and whole body (18)F-fluorodeoxyglucose positron emission tomographic/computed tomographic scans are sensitive for detecting bone metastasis in patients with breast cancer. However, it is often difficult to discriminate between bone metastasis and other nonmalignant bone lesions. Polyostotic fibrous dysplasia is a rare disorder characterized by the osteoid medullary cavity filling with fibrous tissue causing bony expansion. We report the case of a 42-year-old female patient with ductal carcinoma in situ, which appeared to have multiple bone metastases on initial work-up images. Subsequently, the bone metastases were identified as polyostotic fibrous dysplasia. The patient underwent modified radical mastectomy and subsequently visited for a second opinion regarding the bony metastases. She underwent right ilium computed tomography-guided biopsy. Pathology was consistent with fibrous dysplasia. This patient received only adjuvant tamoxifen, and 1.5 years later, there was no evidence of recurrence.