Endosonographic and histopathological staging of extrahepatic bile duct cancer: time to leave the present TNM-classification?

OBJECTIVES

The discrepancy between high rates of sensitivity, specificity, and accuracy for intraductal ultrasonography (IDUS) in extrahepatic bile duct carcinoma and the failure to depict different wall layers as defined by the TNM classification have not yet been elucidated sufficiently.

METHODS

In a prospective study, endosonographic images were correlated with histomorphology including immunohistochemistry. Using IDUS, we examined fresh resection specimens of patients who had undergone pancreato-duodenectomy. For histological analysis, the formalin-fixed and paraffin-embedded specimens were stained by hematoxylin-eosin, elastica-van-Gieson, and immunohistochemically by smooth muscle-actin. To confirm our hypothesis, further cases from the archives were analyzed histopathologically and immunohistochemically.

RESULTS

The various wall layers of the extrahepatic bile duct as described by the International Union Against Cancer are neither histomorphologically nor immunohistochemically consistently demonstrable. Especially, a clear differentiation between tumor invasion beyond the wall of the bile duct (T2) and invasion of the pancreas (T3) by histopathological means is often not possible. Endosonographic images using high-resolution miniprobes similarly confirm the difficulty in imaging various layers in the bile duct wall.

CONCLUSIONS

Most adaptations made by the sixth edition of the TNM classification accommodate to the endosonographic and most of the histopathological findings as demonstrated in our study. In contrast to the new edition, however, our findings suggest to combine T2- and T3-staged tumors into one single class leading to clarification, and improved reproducibility of histopathological staging.