Present by int 黃子豪

Introduction Defining the outermost part of the extrahepatic bile duct (EBD) wall is difficult because it has several histologic characteristics that are different from those of the majority of the other luminal gastrointestinal (GI) tract organs.

Introduction First, the smooth muscle layer of EBD is relatively thin with a variable distribution and amount of smooth muscle fibers along its length.

Introduction Second, the EBD wall consists of intermixed dense fibrous tissue and muscle fibers,

Introduction Third, although most of the GI tract possesses a serosa with a mesothelial lining, the EBD does not have a well developed serosa with which to differentiate the EBD from other surrounding structures.

Introduction Finally, the EBD is surrounded by different structures depending on its site.

Introduction (AJCC) differentiates between T1 and T2 bile duct cancers depending on whether the tumor is confined to the bile duct (T1 classification) or invades beyond the wall of the bile duct (T2)

Introduction Previous definition: loosely richly vascularized connective tissue interlaced with large nerve fibers To examine this issue in more detail, we conducted a study of the distribution of blood vessels and nerve fibers in and along the fibromuscular wall of the EBD.

Materials and Methods Thirty-four EBD specimens were obtained from January to November 2004 Only cases performed within 48 hours of death were included. Tissue from the ampulla of Vater to the proximal end of the EBD above the junction of the cystic duct and common hepatic duct was sampled in each case.

The distribution of blood vessels and nerve fibers were categorized as within, at the junction, or outside of the EBD wall.

The outermost part of the bile duct wall was defined as the limit of dense fibromuscular tissue (mixed dense fibrous tissue and smooth muscle fibers) arranged in a concentric fashion around the EBD lumen.

Distribution of Blood Vessels In the lower EBD, In the middle segment withinatoutside 56 ％ 82 ％ withinatoutside 53 ％ 41 ％ 82 ％

Distribution of Blood Vessels In the upper portions of the EBD, WithinAtoutside 27 ％ 38 ％ 91 ％

Distribution of Nerve Fibers In the lower EBD, In the middle portions WithinAtoutside 50 ％ 41 ％ 68 ％ WithinAtoutside 21 ％ 38 ％ 85 ％

Distribution of Nerve Fibers In the upper EBD, WithinAtoutside 24 ％ 53 ％ 85 ％

DISCUSSION Large blood vessels are important in the evaluation of cholangiocarcinomas arising in the EBD. small-sized and medium-sized blood vessels and nerve fibers are not consistently located along the junction of the bile duct wall

This phenomenon suggests that the junction between dense fibromuscular tissue and loose connective tissue is a real biologic landmark.

In support of this contention, a previous analysis of 222 EBD carcinomas using the same definitions of the bile duct wall as in this study, showed a significant survival difference between T1 and T2 carcinomas.

Some inherent diffuculties: - In the lower portion of the EBD system…hard to tell from the boudary between EBD and pancreas - Preexisting fibrotic disease and tumor- associated desmoplasia.

The destruction or lack of anatomic boundaries will remain a problem in definitive cancer staging A possible alternative method for solving this problem may be to measure the actual depth of invasion from the surface of the bile duct lumen to the deepest portion and use this to assign tumor stage.

Conclusion Eliminating the inclusion of blood vessels and nerve fibers from the definition of tissue intrinsic to the EBD wall may prevent the downstaging of carcinomas, providing a more accurate assessment of prognosis.