Background and study aims: Vascular dilatation seen on percutaneous transhepatic cholangioscopy (PTCS) is diagnostic of intramural invasive carcinoma of the bile duct, but the limitations of the technique, including biopsy, for the diagnosis of intramural extension of bile duct carcinoma have not to our knowledge been investigated before. The aims of the present study were to estimate the thickness of the specimens of bile duct wall taken by biopsy, to assess the sensitivity of PTCS for detecting intramural invasive carcinoma, and to identify the characteristics of the intramural extension of bile duct carcinoma associated with vascular dilatation.
Patients and methods: A total of 135 biopsy, and 16 surgical specimens obtained from 25 bile duct carcinomas were examined for: the thickness of the biopsy specimens and of the mucosa and combined mucosal-fibromuscular layers in the resected common bile ducts and common hepatic ducts; the presence of muscular and neural bundles in the biopsy specimens; the number of invasive carcinomas in the biopsy specimens that had been taken from stenosed regions; and the relation between intramural extension of invasive carcinoma and vascular dilatation.
Results: The mean thickness of the biopsy specimens did not differ from the mean thickness of the mucosa in the resected specimens, but was significantly lower than that of the combined mucosa and fibromuscular layer. Muscular bundles were included in only 13 (14%) of the biopsy specimens, and there were no neural bundles. Carcinomas and invasive carcinomas were diagnosed histologically from the biopsy specimen in 96% and 91% of the cases, respectively. The sensitivity of a single biopsy for diagnosis for invasive carcinoma in stenosed regions was 62%, almost the same as the sensitivity in non-stenosed regions with vascular dilatation (68%). On histologic examination of 16 resected specimens, the sensitivity and specificity of vascular dilatation as a marker of the intramural extension of an invasive carcinoma were 39% and 100%, respectively, and this was significantly more common in invasive carcinomas that were invading the mucosa beyond the adventitia than in those limited to the adventitia.
Conclusion: Histologic examinations of specimens obtained by PTCS-guided biopsy can detect invasive carcinoma in only the superficial layers of the bile duct, such as the mucosa and the shallowest fibromuscular layer. Multiple specimens are needed for the diagnosis of invasive carcinoma because the sensitivity of examination of a single specimen for detecting invasive carcinoma is low. Vascular dilatation is characteristic of carcinoma that is invading the mucosa beyond the adventitia, so the diagnosis of intramural extension of bile duct carcinoma limited to the adventitia, particularly if it has spread to the deeper fibromuscular layer and the adventitia, is difficult to make by PTCS.