Pathological Subtrochanteric Femoral Fracture as the Initial Presentation of Metastatic Thyroid Carcinoma in a Young Adult: A Diagnostic Challenge.

Pathological fractures should be suspected in young adults presenting with low-energy femoral fractures. We report a 39-year-old woman who sustained a subtrochanteric fracture after trivial trauma while exiting a car. Imaging demonstrated multiple lytic lesions involving the femur and pelvis, with pulmonary nodules suspicious for metastases. Laboratory evaluation showed biochemical hyperthyroidism. Intramedullary fixation was performed after discussion with the Oncology Multidisciplinary Team (MDT), and histopathology of femoral reamings confirmed metastatic thyroid carcinoma, likely follicular type. Thyroid ultrasound showed no suspicious nodules, highlighting discordance between imaging and histology. This case emphasises the importance of considering pathological fracture in atypical presentations, performing oncologic evaluation before definitive fixation, and relying on tissue diagnosis when imaging is inconclusive.