At staging 8 months after initial symptoms, computed tomographic and fluorine 18 (18F)–labeled fluorodeoxyglucose positron emission tomographic scans showed extensive systemic involvement, the latter showing enhancement in the right maxillary sinus, right temporalis muscle, skull base, mediastinum, retroperitoneum, mesenteric lymph nodes, bones of the thorax and pelvis, both femurs, abdominal soft tissue, and right periformis muscle (Figure 1D). Bone marrow biopsy revealed paratrabecular lymphomatous infiltrates, composing 10% to 20% of the marrow. Final staging was of stage IVE follicular lymphoma. The patient began receiving cyclophosphamide, doxorubicin hydrochloride, vincristine sulfate, and prednisone chemotherapy that resulted in resolution of infiltrates on 18F-fluorodeoxyglucose positron emission tomographic scanning 14 months after symptom onset (Figure 1E). However, repeated bone marrow biopsy showed residual disease. He then received tositumomab (BEXXAR), an iodine I 131–labeled anti-CD20 monoclonal antibody, to target and kill the malignant B lymphocytes, resulting in negative marrow biopsy results 2 months later.