An 83-year-old woman complained of mild pain and a thigh mass that had been increasing in size over the past year. A, An anteroposterior radiograph of the knee is relatively unremarkable. B-D, MRI, however, demonstrates a large lesion that permeates through the bone with a large, circumferential soft-tissue mass. These findings are typical of lymphoma. Lymphoma should usually be considered when MRI demonstrates a large bone lesion despite relatively normal radiographs.