Clinicopathologic Study On Perineural Invasion In Hilar Cholangiocarcinoma

Hilar cholangiocarcinoma often produces perineural invasion extending to extrabiliary sites, while the mechanism of that procedure remains unclear. Despite advances in diagnostic modalitities and resection rate, in most patients with hilar cholangiocarcinoma the lesion is at an advanced stage when the diagnosis was first made and the prognosis remains dismal. Surgical resection is the best therapeutic strategy, while the recurrence rate is very high. The spread of tumor through perineural space has been described in a variety of human tumors, and many authors have emphasized nerve dissection together with tumor resection as a more radical approach. Although previous study has shown perineural invasion had harmful effects on the prognosis of patients with hilar cholangiocarcinoma, diversity of perineural invasion incidence in various reports is tremendous. Up to now, the pathway and mechanism of perineural invasion remains unclear and no detailed studies on the distribution of nerve plexuses around hepatic portal have been conducted. Therapeutic strategies against perineural invasion still limit to animal experiment, and there is short of satisfying animal model of hilar cholangiocarcinoma. A better understanding of perineural invasion is essential for determining the optimal extent of resection, increasing the cure rate and preventing the postoperative recurrence of tumor.AIM: (1) To summarize the incidence and special patterns of perineural invasion in hilar cholangiocarcinoma and find out the distribution of nerve plexuses around hepatic portal. (2) To elucidate the characteristic and mechanism of perineural invasion in hilar cholangiocarcinoma, and find out its association with the microvessels and microlymphatics. (3) To establish human hilar cholangiocarcinoma cell line orthotopic implantation tumor model in nude mice and observe its biological characteristics.METHODS: A clinicopathologic study was conducted on sections from 75 patients with hilar cholangiocarcinoma to summarize the incidence and modes of perineural invasion. Immunohistochemical stains for CD34 and D2-40 in 30 cancer tissue were performed to clarify the associstion of perineural invasion with microvessels and microlymphatics. Sections of different decks of hepatoduodenal ligament from 5 autopsy cases were scanned and handled by computer to display the distribution of nerve plexuses around hepatic portal. Cultured human hilar cholangiocarcinoma cell line QBC939 was injected into the space between hilar bile duct and portal vein through micro-injector in nude mice. Morphological and pathological features were studied after 15 days.RESULTS: (1) The overall incidence of perineural invasion was 92 per cent (69 of 75 patients). However, the incidence of perineural invasion did not show any remarkable differences among various differentiated adenocarcinoma groups. Logistic regression analysis identified penetration of bile duct was the only factor that correlated significantly with perineural invasion (P<0.01). (2) Five patterns were observed as the tumor cells invading nerve fibers. (3) The microvessel density (MVD) in well differentiated adenocarcinoma group was significantly less than that in moderately and poorly differentiated groups (P<0.05), while no significant difference was detected in MVD between the other two groups (P>0.05). In spite of finding tumor cells could invade microvessels and microlymphatics, no association between perineural invasion with either lymphatic or vascular invasion was found by immunohistochemistry stains for CD34 and D2-40 respectively. (4) Three nerve plexuses in the hepatoduodenal ligament and Glisson's sheath were classified and they all surrounded the great vessels very closely. (5) 1×10~6 of tumor cells could be injected into each nude mouse safely. The successful rate of hilar cholangiocarcinoma cell line orthotopic implantation tumor was 100% after 15 days.CONCLUSION: Perineural invasion is common in hilar cholangiocarcinoma and it does not develop via the lymphatic or vascular network but is a continuous extension from the primary tumor. Nerve plexus around the membrana adventitia should be divested completely during the radical excision of hilar cholangiocarcinoma. Human hilar cholangiocarcinoma cell line orthotopic implantation tumor model can be successfully established in nude mice.