Some soft tissue neoplasms will exhibit variable degrees of avidity for skeletal radiotracer. The most common neoplasms to demonstrate skeletal radiotracer uptake being breast, lung, colon, melanoma, and neuroblastoma. The mechanism is not well understood, however, it is thought that this uptake is secondary to either radiotracer binding to tumor calcification (such as in mutinous carcinoma of the colon) or binding to a macromolecule secreted by the neoplasm.
Pleural effusions have been found to take up radiotracer approximately 61 % of the time, with an equal uptake in both benign and malignant effusions.