Cotton-induced pseudotumor of the femur

Twenty-five years prior to presentation a I l-year-old man had a femoral fr acture stabilized with a 4.5 mm AO/ASIF steel plate. The femur healed uneve ntfully and the patient was asymptomatic for the following 20 years. He the n noticed a slow-growing swelling of the left thigh associated with a degre e of weakness. Radiographs of the femur 25 years after fracture stabilizati on showed a massive expansive osteolytic process surrounded by a rim of bon e. Magnetic resonance imaging (MRI) confirmed the presence of a large tumor . Since malignancy could not be excluded the patient underwent incisional b iopsy. The histologic findings were nonspecific. Because of persistent symp toms the lesion was marginally excised. Intraoperatively a folded cotton sp onge was found adjacent to the femur. Histopathologic investigation confirm ed a foreign body reaction probably related to the retained cotton sponge. Reactive, foreign-body-induced change may mimic bone and or soft tissue mal ignancies.