Findings: A bone scan demonstrates ill-defined soft tissue activity within the right abdomen without discrete visualization of the right kidney. Increased radiopharmaceutical activity is also seen in the region of the sphenoid sinus secondary to known expansile mucocele. Increased radiopharmaceutical activity is also seen within the mid right tibia, secondary to prior fracture.

Diagnosis: Renal cell carcinoma.

Discussion: Extraosseous accumulation of technetium 99m MDP radiopharmaceutical can occur in numerous conditions. Generalized retention in soft tissue can be seen in renal failure. Abnormal accumulation can be seen in malignant pleural effusions and malignant ascites. Pulmonary uptake can be seen in radiation pneumonitis and pneumocystis carinae pneumonia. Diffuse splenic accumulation can be seen in numerous hematologic disorders. Cardiac activity can be seen in myocardial infarction, unstable angina, myocardial perfusion, pericarditis, ventricular aneurysm, and amyloidosis.

Diffuse uptake in multiple organs can be seen in hypercalcemic states, usually induced by hyperparathyroidism. Muscular uptake can be seen in numerous conditions including polymyositis, muscular dystrophy, and dermatomyositis. Focal muscular activity can be seen in myositis ossificans.

Many malignant tumors demonstrate uptake of technetium 99m MDP. This case demonstrates uptake of radiopharmaceutical within a large renal cell carcinoma which is clearly demonstrated on the patient's abdominal CT.

References:
Mettler FA, et al. Skeletal System. In: Essentials of Nuclear Medicine Imaging,
3rd Edition, Editors, Mettler FA, et al. W. B. Saunders Co., Philadelphia; 1991:221-224.

Murray IPC. Bone Scintigraphy: The Procedure and Interpretation.
In: Nuclear Medicine in Clinical Diagnosis and Treatment, V 2. Editors Murray IPC
and Lell PJ. Churchill Livingstone, Edinburgh; 1994:925-931.

Weiffleder R. et al. Nuclear Imaging. Primer of Diagnostic Imaging. Mosby, St. Louis; 1997:862.

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