Nonosseous Uptake on Bone Scan in Adenocarcinoma of Unknown Primary Origin

Two patients without histories of cancer underwent Tc-99m MDP bone scans as part of evaluations of pain and abnormal laboratory and radiologic findings. Both scans showed abnormal soft tissue uptake in tumor deposits and in visceral organs associated with hypercalcemia and metastatic calcification. One scan showed diffuse increased bone uptake (superscan pattern), and the other revealed focal metastatic bone uptake. Adenocarcinoma of unknown primary (AUP) origin was subsequently identified in both patients. AUP occurs in multiple organs more than 50% of the time, with bone involvement in 4% to 31% of cases. The patients described here reflect the variety of patterns of osseous and nonosseous uptake of diphosphonate bone agents in patients with AUP.