Rheumatoid nodule of the foot: MRI appearances mimicking an indeterminate soft tissue mass

Subcutaneous rheumatoid nodules occur commonly in advanced cases of rheumatoid arthritis, but only rarely appear in the feet. We present a case of a subcutaneous rheumatoid nodule arising in the heel pad of a 68-year-old man with a long history of rheumatoid arthritis, along with a review of the literature. The appearance of the mass on MRI is illustrated and correlated with the histologic findings. The MRI appearance of a subcutaneous rheumatoid nodule is that of a nonspecific ill-defined mass with long T1- and long T2-relaxation times. A differential diagnosis for similar appearing masses is offered.