Differentiation of retroperitoneal tumor using positron emission computed tomography.

Positron emission computed tomography (ECT) with 11C-DL-tryptophan and 11C-aminocyclobutanecarboxylic acid (11C-ACBC) has produced some promising results in patients with retroperitoneal masses. This brief report gives an example of one patient in whom a retroperitoneal mass could not be differentiated from the pancreas by transmission computed tomography but was suspected to be of pancreatic origin based on arteriographic findings. The ECT scans with 11C-DL-tryptophan showed a normal pancreas, whereas the tumor localizing agent 11C-ACBC concentrated in a tumor surrounding the tail and body of the pancreas. This approach with dual radiopharmaceuticals for the differentiation of metabolically active neoplasms and normal tissues warrants further investigation.