[An investigation of the mode of local spreading of biliary tract carcinoma to microvascular and neural structure]

Abstract

To understand the spreading mode of extrahepatic bile duct carcinoma and gallbladder carcinoma, 170 specimens (86 of which had gallbladder carcinoma while the remaining 84 had extrahepatic bile duct carcinoma) were histo-pathologically studied. In addition, experiments utilizing a canine model were also concurrently conducted in order to gain a greater understanding of relationship between micrometastasis of extrahepatic bile duct carcinoma and microstructures of lymphatics, veins and nerves of biliary tract. The results were as follows: 1) Invasion of the local lymphatics, veins and nerves was found to increase as the grade of tumor penetration into the wall of the biliary tract increased. In addition, it was observed in cases of extrahepatic bile duct carcinoma, a high rate of lymphatic involvement when tumor invasion involved the fibrous muscle layer. However, in cases of gallbladder carcinoma there was no lymphatic involvement even though it also had tumor invasion of the proper muscular layer. 2) In the case of gallbladder carcinoma, correlation of the micrometastasis to lymphatics, veins and nerves was seen, but in cases of extrahepatic bile duct carcinoma, no relationship to micrometastasis of veins and nerves was observed. 3) Anatomically, the study noted rich networks of lymphatics and nerves in the hepatoduodenal ligament. Thus, the rate of micrometastasis to these lymphatics and nerves was more extensive than the observed positive rate of the micrometastasis to veins. 4) Although no direct relationship between nerves and lymphatics was found, it was noted that perineural space was extended in the cases with lymph stasis. There was a network of blood-vessels of nerves and the pericholedocal vascular plexus in the hepatoduodenal ligament. Perineural invasion of carcinoma cells account for the anatomical distribution the surrounding lymphatics and veins. In conclusion, the localization and distribution of micrometastasis from extrahepatic bile duct carcinoma to the involved lymphatics, veins and nerves structures seemed to correlate to the microanatomy of the biliary.