Background/purpose: By the time undifferentiated carcinoma is detected, it has formed a large mass, and it is reportedly difficult to pathologically observe its relationship with the pancreatic duct. In this study, we examined the pancreatic ducts of seven patients of surgical samples, and pathomorphologically investigated the relationship between the adenocarcinomatous and sarcomatous components and the pattern of tumor extension. In addition, we evaluated the usefulness of pancreatic juice cytology by comparison with the findings of the main pancreatic duct (MPD).
Methods: Seven primary undifferentiated carcinomas of the pancreas (from three male and four female patients with a mean age of 59 years) were analyzed. Histopathological evaluation was based on the WHO diagnostic criteria. Pancreatic juice cytology was performed and evaluated in two patients.
Results: All the undifferentiated carcinomas contained adenocarcinomatous and sarcomatous components, and two had a distinct glandular structure. However, we could not pathomorphologically confirm the continuity of the adenomatous with the sarcomatous components in any of the patients. Three undifferentiated carcinomas contained osteoclast-like giant cells. Pathological observation of the tumor and MPD was possible in three of the seven undifferentiated carcinomas. PanIN-3 was observed in the MPD of three patients, suggesting extension into the MPD. In one of these three, the tumor presented intraductal growth in the MPD, and preoperative pancreatic juice cytology revealed atypical cells with osteoclast-like giant cells. In the remaining two, the tumor extraductally compressed the MPD upward.
Conclusions: Undifferentiated carcinoma showed two patterns of cancer extension: (1) invasion and expansive growth during the sarcomatous transformation of adenocarcinoma, and (2) intraductal extension. In addition, some undifferentiated carcinomas showed extension in the MPD. Of note, postoperative pancreatic juice cytology may be useful for the diagnosis.