Gastric- and intestinal-type marker expression in invasive ductal adenocarcinoma of the pancreas.

Background: Although invasive ductal adenocarcinoma of the pancreas (PDAC) manifests as a relatively uniform histomorphological feature of the pancreatobiliary type, it may be complicated by metaplastic changes and heterogeneous gastric and intestinal elements. This study aimed to investigate the complication rate and clinicopathological significance of such heterogeneous elements.
Methods: Fifty-nine patients who underwent resection of PDAC were examined in this study. Immunohistochemically, tumors showing high expression (>25%) of the intestinal-type (INT) marker CDX2 were classified as PDAC with INT. Those with high expression (>25%) of the gastric-type (GAS) marker MUC5AC were classified as PDAC with GAS, while those with high expression of both markers were classified as PDAC with INT/GAS. These patients were compared with those with PDAC of the negative group in which neither markers was highly expressed to examine their clinicopathological significance.
Results: In the 59 patients, 31 (52.5%) showed high CDX2 or MUC5AC expression. Twenty-eight patients (47.5%) belonged to a negative group, 11 (18.6%) to a PDAC with INT group, 15 (25.4%) to a PDAC with GAS group, and 5 (8.5%) to a PDAC with INT/GAS group. No significant differences were observed for age, gender, size, localization, T classification, or prognosis among the four groups. Although the PDAC with GAS group had well differentiated types significantly more than the other groups, the rate of lymph node metastasis in this group was significantly higher (PDAC with GAS: 73%; other groups: 36%).
Conclusion: Complications with heterogeneous elements are not uncommon in PDAC, and this should be considered during the diagnosis and treatment of PDAC along with histogenesis of the disease.