Importance and Difficulty of Differentiating BMA-induced AFF Prodromal Symptoms from Hormonal Therapy-related Femoral Pain

We herein report a case of breast cancer in a 74-year-old woman treated with exemestane as fourth-line hormonal therapy and bone-modifying agents for long time. She suddenly developed a right femoral shaft fracture during treatment. Her femoral fracture had a beaking sign on radiogram. Given this finding, her fracture was ultimately diagnosed as atypical femoral fracture (AFF). In this case, it was difficult to recognize the difference between groin pain as a prodromal symptom of AFF and that due to an adverse reaction to hormonal therapy. Therefore, clinicians should recognize the difficulty of this differentiation and consider the situation with caution.