Impending Atypical Femoral Fracture in Patients With Medullary Thyroid Cancer With Skeletal Metastasis Treated With Long-term Bisphosphonate and Denosumab.

Atypical femoral fractures (AFFs) occur in osteoporosis patients receiving long-term bisphosphonate. Atypical femoral fractures also occur in cancer patients receiving long-term bisphosphonate or denosumab, but the prevalence is low. We describe a 53-year-old woman with a history of medullary thyroid cancer and skull metastasis who was prescribed bisphosphonate for 6 years and denosumab for 1.5 years, consecutively. Bone scintigraphy performed because of spontaneous groin pain showed uptake in the lateral aspect of the left femur, which was confirmed as impending AFF. In oncological patients receiving long-term bisphosphonate or denosumab, AFF should be included as a differential diagnosis with focal femoral findings.