Incomplete Atypical Femoral Fracture Related to Long-term Bisphosphonate Therapy in a Case of Accessory Breast Cancer with Bone Metastasis

Abstract

A 76-year-old woman presented with a 3-cm-sized tumor in the right axilla, with dermal infiltration. Core needle biopsy revealed invasive ductal carcinoma, and immunohistochemical findings revealed positivity for estrogen receptor (ER) and negativity for progesterone receptor (PgR) and HER2. She was diagnosed as having accessory breast cancer with multiple bone metastases and was classified as stage IV. Bisphosphonate (BP) therapy was initiated, and 78 months after starting BP therapy, she developed discomfort in her right femoral area, with pain on walking. Plain radiographs revealed localized thickening of the right femoral lateral bone cortex. An incomplete transverse fracture on computed tomography and low signal intensity on T1-weighted magnetic resonance images in the same location suggested repair process after an atypical femoral fracture because of long-term BP therapy. Bone scintigraphy, 1 year earlier, had shown slight right-sided lateral femoral uptake. BP therapy was discontinued, and the pain improved with conservative management. At present, 30 months later, no skeletal-related adverse events have occurred, and the atypical femoral fracture is stable. In this case, a suspicion of atypical femoral fracture based on symptoms of advanced disease prompted the diagnosis of an incomplete fracture. Atypical femoral fractures must be suspected in patients on long-term BP therapy.