Clinical study on the efficacy of contrast enhanced CT scan for the diagnosis of pancreatic cancer. With special reference to the evaluation of new CT findings useful for differentiation from tumor-forming pancreatitis

Differential diagnosis of pancreatic cancer (PCA) and tumor-forming pancreatitis (TFP) is made based on early-phase staining pattern in contrast enhanced X-ray CT (CE-CT). In the present study, I evaluated also late-phase findings and findings by tumor diameter and identified new CE-CT findings useful for differential diagnosis. CE-CT findings useful for the diagnosis of small pancreatic cancer were also evaluated. Included in the present study were 68 PCA cases and 39 TFP cases examined in this and affiliated facilities over the last 11 years. In the early phase, density in tumorous areas was useful for differentiating PCA and TFP, because 94 % of tumorous areas showed hypodensity in PCA, while 85 % showed isodensity in TFP. However, differentiation was difficult due to hypodensity, similar to PCA, in the remaining 15% of TFP. The following five findings were found to be PCA-specific with specificity rates of 95% and over: non-staining area (early phase), hyperdensity spot and line (early phase), hyperdensity zone (early and late phase) and hyperdensity (late phase). The diagnosis of PCA could be made more accurately using these findings. The incidence of non-staining area or hyperdensity spot and line, early-phase findings, was also useful for diagnosis, as it increased with the tumor size, from 13 % when the tumor size was 20 mm or smaller to 80% when it was 21 mm or larger. The incidence of late-phase hyperdensity or hyperdensity zone was higher for smaller tumors: 71% for tumors of 20mm or smaller. Therefore, hyperdensity in tumorous areas in the late phase is thought to be useful in the diagnosis of small pancreatic cancer. (author)