A national database analysis of acinar cell carcinoma of the pancreas, a histologically, epidemiologically, and biologically distinct entity increasing in incidence

Background: Pancreatic acinar cell carcinoma is a rare exocrine malignancy that is distinct from pancreatic ductal adenocarcinoma. We sought to describe its changing incidence, compare its natural history to that of pancreatic ductal adenocarcinoma, and evaluate impact of treatment modalities using the National Cancer Data Base, and Surveillance Epidemiology and End Results datasets. Methods: Patients with histologically confirmed diagnosis were identified from the National Cancer Data Base and Surveillance Epidemiology and End Results. Parametric univariate analyses were performed to compare patient characteristics, tumor types and outcomes. Incidence trends were calculated using Surveillance Epidemiology and End Results data and unadjusted Kaplan-Meier Survival analysis was performed using data from the National Cancer Data Base. Results: Incidence of acinar cell carcinoma significantly increased by 73% over the study period compared to only 22% for ductal adenocarcinoma (P<0.01). Unadjusted and adjusted stage-specific survival was substantially superior for acinar cell carcinoma versus ductal adenocarcinoma in all stages. Pancreatic acinar cell carcinoma demonstrated lower age at diagnosis, larger and lower grade tumors, was less likely to demonstrate histopathologic lymphovascular invasion, and more likely to undergo curative-intent resection with lower positive margins compared to ductal adenocarcinoma. Amongst resected patients, ductal carcinoma histology remained the strongest independent predictor of increased mortality hazard compared to pancreatic acinar cell carcinoma. Conclusions: Acinar cell carcinoma is a less aggressive malignancy with a significantly rising incidence of unknown etiology and better overall survival in both unadjusted analysis and after adjustment for clinically relevant predictors of mortality. 10 surgical resection. These findings, along with the improved overall survival at all stages, suggests that PACC is a less aggressive malignancy than PDAC. The 73% increase in incidence over a 12 year study period is of significant interest. The study demonstrated that the incidence is increasing at a much faster rate than PDAC. The reason for the increasing incidence is unknown and is a subject for further investigation which should be followed with interval studies. Possible explanations for this increased incidence is improvements in the ability to identify this histologic subtype, increased incidental identification during abdominal imaging for other purposes, or due to genetic factors.