Detection of Small (<=20 mm) Pancreatic Adenocarcinoma: Histologic Grading and CT Enhancement Features

We read with great interest the article by Yoon and colleagues in the May 2011 issue of Radiology (1). We greatly appreciate the study, but there are some concerns to be discussed. The authors inappropriately use the term “multiphasic” multidetector computed tomography (CT). Their study protocol provided an unenhanced scan, a pancreatic parenchymal phase scan, and a portal venous phase scan. Only pancreatic parenchymal phase CT was performed in two patients, and only portal venous phase CT was performed in nine patients. The term multiphasic (“tri-” or “quadriphasic” CT) is standardized and refers only to the helical CT volume acquisition at different phases after intravenous injection of a bolus of contrast material (2). In the conclusion of the abstract, the authors wrote: “The prevalence of isoattenuating pancreatic cancers differed significantly according to tumor size and cellular differentiation. Most small isoattenuating pancreatic cancers showed secondary signs.” These conclusions are not supported in Materials and Methods. The cellular differentiation grading and the histologic features of “loose fibrosis” are not described in the Materials and Methods or Results sections. Furthermore, tumor size at CT was correlated with tumor size at histologic examination in only a few cases. Microscopy is, of course, considered the standard of reference for the measurement of tumor size. In addition to using main pancreatic duct dilatation or the interrupted duct sign, which are indicators of an isoattenuating cancer (3), to detect a small pancreatic adenocarcinoma at CT, we suggest performing delayed-phase imaging in association with dual-phase helical CT (triphasic CT) (4).