Radionuclide imaging of soft tissue masses with Tc-99m DTPA.

A scintigraphic study was carried out on 48 patients presenting with palpable soft tissue masses. Imaging was carried out using Tc-99m DTPA in three phases (dynamic, blood pool after 5 minutes, followed by late scans after 2 hours). The resultant uptake of the agent was categorized as consistently positive (14 cases), initially positive but progressively negative (7 cases), initially negative but progressively positive (7 cases), and consistently negative (20 cases). Histopathologic examinations were carried out for all cases following biopsy. A variety of malignant and benign masses were found to localize DTPA, whereas all masses that did not concentrate the agent were proven to be lipomas. In order to determine whether the uptake of DTPA bore any relationship to blood flow, additional studies using Tc-99m labeled red cells were carried out on 15 patients with soft tissue tumors. There was no correlation between blood flow or pooling and the degree of Tc-99m DTPA uptake by the palpable masses. The sensitivity of DTPA uptake as indicative of nonlipomatous tissue was 100%, and its specificity was 91%. The predictive probability that a lesion was a liopoma if there was no DTPA uptake at any phase was 100%.