Immunohistochemical Evaluation of the Tumor Immune Microenvironment in Pancreatic Ductal Adenocarcinoma

<b>Background</b>: Pancreatic ductal adenocarcinoma is an aggressive neoplasm with a complex carcinogenesis process that must be understood through the interactions between tumor cells and tumor microenvironment cells. <b>Methods</b>: This study was retrospective with a chronological extension period of 16 years and included 56 cases of pancreatic ductal adenocarcinoma. This study identified, quantified, and correlated the cells of the tumor immune microenvironment in pancreatic ductal adenocarcinoma with major prognostic factors as well as overall survival, using an extensive panel of immunohistochemical markers. <b>Results</b>: Three tumor immunotypes were identified: subtype A (hot immunotype), subtype B (intermediate immunotype), and subtype C (cold immunotype). Patients with immunotype C exhibit considerably higher rates of both pancreatic fistulas and acute pancreatitis. Immunotypes B and C significantly increased the risk of this complication by factors of 3.68 (<i>p</i> = 0.002) and 3.94 (<i>p</i> = 0.001), respectively. The estimated probabilities of fistula formation for each immunotype are as follows: 2.5% for immunotype A, 25% for immunotype B, and 28% for immunotype C. There was a statistically significant difference in median survival times according to tumor immunotype (<i>p</i> < 0.001). Specifically, patients with immunotype C tumors had a median survival time of only 120.5 days, compared to 553.5 days for those with immunotype A and 331.5 for immunotype B tumors. <b>Conclusions</b>: The identification of the immunotype of pancreatic ductal adenocarcinoma can be a predictive factor for the occurrence of complications such as pancreatic fistula as well as for overall survival.