To evaluate the influence of various clinicopathologic factors on survival, a computer analysis was performed on 70 patients who underwent resection for bile duct carcinoma. Univariate analysis of overall survival involving all the patients identified 10 factors that were associated with a significant outcome: location of primary lesion (p = 0.01), pancreatic invasion (p = 0.004), duodenal invasion (p = 0.005), macroscopic and microscopic vascular involvement (p = 0.009 and p = 0.04), perineural invasion (p = 0.02), lymphatic vessel involvement (p = 0.04), lymph node metastasis (p = 0.02), histologic type (p = 0.02), and depth of cancer invasion (p = 0.04). However, when the interactive effects of these factors were taken into account, the pancreatic invasion and perineural invasion were selected as the two most significant prognostic factors in a multivariate analysis using the Cox stepwise proportional hazards model. The age, sex, size of the tumor, macroscopic type of lesions, hepatic infiltration, serosal invasion, resected surgical margin at the proximal and distal ends, exposed surgical margin, peritoneal dissemination, and hepatic metastasis were not significantly associated with prognosis.

To elucidate the clinical significance of perineural invasion on bile duct cancer, a clinicopathologic study was performed on 70 resected patients with bile duct carcinoma. The overall incidence of perineural invasion in the resected specimen was 81.4%. There seemed to be no correlation between perineural invasion and site, size of the tumor, and lymph node metastasis. A significant correlation was observed, however, between macroscopic type, microscopic type, depth of invasion, and perineural invasion. Perineural invasion index (PNI) was defined as the ratio between the number of nerve fibers invaded by cancer and the total number of nerve fibers with and without cancer invasion. Perineural invasion index was significantly higher at the center compared with the proximal and distal part of the tumor (p less than 0.001). The 5-year survival rate for patients with perineural invasion was significantly lower (p less than 0.05) than that for those without perineural invasion (67% versus 32%).

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