What causes uptake of technetium-99m methylene diphosphonate by tumors? A case where the tumor appeared to secrete a hypercalcemia-causing substance.

A patient exhibited an unusual constellation of findings: His extraosseous lymphoma sequestered [99mTc]MDP, a bone-seeking agent, while at the same time it appeared to produce a factor that caused hypercalcemia. The dispersed lymphoma cells took up more [99mTc]MDP in vitro than did cultured lymphoblasts suggesting that the in vivo sequestration may have been, at least in part, an active intracellular process.