Polyostotic Fibrous Dysplasia Mimicking Multiple Bone Metastases in a Patient with Ductal Carcinoma In Situ
A 42-year-old woman was admitted to the breast clinic of a university hospital with a palpable mass in the right breast originally detected in a local clinic. According to her medical records, there were no signs of nipple retraction or skin abnormalities. Breast ultrasonography showed a 1.2-cm microlobulated heterogeneously hypoechoic mass in the lower inner quadrant of the right breast. A core needle biopsy was performed, and ductal carcinoma in situ (DCIS) was diagnosed. The patient had no past medical or family history of breast disease and had no bone pain symptoms.\nShe underwent chest radiography as a baseline study for general anesthesia, which showed osteolytic lesions of the right second, third, eighth ribs, and the left fourth rib (). A chest CT was performed and revealed multiple asymmetric osteolytic lesions in the previously enumerated ribs suggesting multiple bone metastases. She was indicated for a whole-body bone scan to identify distant metastases. The scan revealed lesions of the right parietal and occipital bones, cervical, thoracic, lumbar, sacral (CTLS) spine, bilateral scapulae, multiple ribs, bilateral pelvic bones, right femur, tibia, fibula, right tarsal bone, sternum, and right humerus (). 18F-FDG PET/CT revealed an increased uptake in the right femur, right ninth and left fourth ribs, and T-L spine consistent with multiple bone metastases. Serum laboratory test results and tumor markers were not increased as follows: calcium, 8.9 mg/dL; phosphorus, 3.2 mg/dL; alkaline phosphatase, 85 IU/L; carcinoembryonic antigen, 0.807 ng/mL; carbohydrate antigen 15-3, 3.87 U/mL.\nThe patient's medical history included a modified radical mastectomy of the right breast out of concern for a possible hidden malignancy. Histopathological examination showed a 2.0×1.6-cm DCIS with nuclear grade 2, and no metastatic lymph nodes detected out of the 24 dissected axillary lymph nodes. Immunohistochemistry studies showed positive staining for estrogen receptor protein and progesterone receptor protein, and negative staining for human epidermal growth factor receptor 2 (score 1). The patient underwent a postoperative pelvic bone biopsy given the histopathological stage, which was nondiagnostic.\nThe patient visited another hospital for a second opinion, and we conducted a multidisciplinary review. The final histopathological report by the pathologist confirmed the previous diagnosis of DCIS (). Radiological evaluation demonstrated the aforementioned results and was not able to exclude the possibility of multiple bone metastases. We recommended a repeat bone biopsy based on the knowledge that distant metastasis after a diagnosis of pure DCIS is rare. The patient underwent right ilium CT-guided biopsy, which revealed fibro-osseous lesions consistent with fibrous dysplasia (). She only received tamoxifen (20 mg daily) endocrine therapy. At 1-year follow-up, a whole-body bone scan was performed (). At 1.5 years, a 18F-FDG PET/CT scan revealed only persistent increased uptake () without evidence of recurrence.