Renal cell carcinoma presenting as a "hot" lesion in kidney, with "cold" metastasis in the skeleton.

Skeletal scintigraphy is useful for detecting primary renal carcinomas and associated osseous metastatic deposits. Usually, renal masses present as photon-deficient foci, and osseous metastases, as foci of increased response. A case is presented with the unusual combination of focal increased Tc-99m MDP localization to the primary renal cell carcinoma and photopenic osseous metastatic foci. Proposed mechanisms are discussed.