CD34+ fibrocytes in neoplastic and inflammatory pancreatic lesions.

Besides its function as a matrix-producing cell, the CD34+ fibrocyte has been reported to be an antigen-presenting cell capable of priming naive T cells in situ. Therefore, it has been claimed that the CD34+ fibrocyte may play an important role in host response to tissue damage. The objective of the present study was to analyze the presence and distribution of CD34+ fibrocytes and smooth muscle actin (SMA) reactive myofibroblasts in relation to the underlying pancreatic disease. We investigated a total of 12 pancreatic adenocarcinomas, 7 endocrine tumors of the pancreas, and 8 cases of chronic pancreatitis; in 11 cases, normal pancreatic tissue was available. The stroma of normal pancreatic tissue harbored diffusely scattered CD34+ fibrocytes. Chronic pancreatitis was characterized by an increased number of stromal CD34+ fibrocytes paralleled by a gain of SMA reactive myofibroblasts which were not observed in the normal pancreatic stroma. The stroma of pancreatic ductal adenocarcinomas and endocrine tumors was devoid of CD34+ fibrocytes or showed at least a focal loss of this cell type, whereas SMA reactive myofibroblasts were detected in both endocrine tumors and adenocarcinomas. We conclude that detection of CD34+ fibrocytes may constitute an adjunctive tool in distinguishing chronic pancreatitis from ductal adenocarcinoma since the absence of this cell population strongly favors a neoplastic process. Moreover, CD34+ fibrocytes and myofibroblasts appear to be involved in stromal remodeling associated with chronic pancreatitis and ductal adenocarcinoma.