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Purpose Primary central nervous system lymphoma (PCNSL) accounts for approximately 3% of all primary brain tumors and 1% of all non-Hodgkin lymphomas. Detection of systemic spread of PCNSL, although rare (4%), is very important since therapy is usually modified. Contrast-enhanced computed tomography (CT) is commonly used for systemic staging of PCNSL. No previous case report is available in the published literature elaborating the potential contribution of F-18 FDG PET in systemic staging of PCNSL. The purpose of this case report was to document the potential usefulness of F-18 FDG-PET in the detection of occult systemic involvement in PCNSL. Materials and methods A 50-year-old, immunocompetent, male patient completed successful treatment of PCNSL. As part of a routine pretransplant evaluation he had an F-18 FDG PET coregistered with CT (PET-CT). The PET-CT results were then compared with those of contrast-enhanced CT of the chest, abdomen, and pelvis. Results The PET-CT examination detected multiple sites of extranodal systemic disease that were not seen in the contrast-enhanced CT of the chest, abdomen, and pelvis (both studies were performed within 24 hours of each other). Percutaneous ultrasound guided biopsy confirmed the presence of systemic spread of PCNSL. The patient's subsequent therapy was modified to include rituximab with cyclophosphamide, doxorubicin, vincristine, prednisone (R-CHOP). A follow up PET-CT confirmed resolution of systemic spread. Conclusion F-18 FDG PET coregistered to CT may be a useful examination in the detection and monitoring for systemic spread of the disease in PCNSL patients.

Tc-99m DTPA scintigraphy of most renal tumors characteristically discloses a vascular mass, without retention of activity on serial images. Two cases, encountered during hypertensive work-up, are presented with vascular renal masses and persistent DTPA uptake. Oncocytoma was confirmed pathologically in both cases. The authors conclude that renal oncocytomas have a relatively distinctive scintigraphic appearance, which may permit accurate preoperative diagnosis.

An In-111 WBC study showed intense periarticular uptake in both knees of a patient being investigated to exclude joint infection before total knee replacement surgery for advanced osteoarthritis. Infection was subsequently excluded. Patients with synovitis secondary to active osteoarthritis can have intense synovial uptake of labeled WBCs. This should be considered as a cause of false-positive scans in the investigation of septic arthritis with labeled WBCs.