Published online Mar 28, 2018. doi: 10.3748/wjg.v24.i12.1332
Peer-review started: February 13, 2018
First decision: February 24, 2018
Revised: March 5, 2018
Accepted: March 7, 2018
Article in press: March 7, 2018
Published online: March 28, 2018
Cholangiocarcinoma (CCA) is a rare malignancy with poor prognosis. Complete surgical resection is the only treatment with the potential for cure, and the status of the final ductal margin is strongly associated with prognosis. Intraoperative frozen section diagnosis (FSD) of the bile duct margins has traditionally been used to guide the extent of operative resection, but its usefulness has been controversial until now.
Because of the rarity and locoregional anatomical complexity of CCA, few centers have substantial clinical experience of managing this disease, and few pathologists have expertise in characterizing resected specimens accurately. In addition, quality of FSD samples is very low. Hence, discordance between FSD and permanent section diagnosis (PSD) that reuses frozen samples often occurs.
The primary purpose of this study was to examine reliability of intraoperative FSD to evaluate the margin status. The secondary purpose was to clarify clinical relevance of borderline lesions that could not be definitely determined whether malignant or benign. Borderline in the present study included such lesions as low-grade and intermediate-grade dysplasia [biliary intraepithelial neoplasia (BilIN)-1 and BilIN-2] and lesions indefinite for neoplasia.
We retrospectively analyzed 74 consecutive patients who underwent surgery for extrahepatic CCA (eCCA) from 2012 to 2017, during which FSD of bile duct margins was performed. They consisted of 40 distant CCAs (dCCAs) and 34 perihilar CCAs (pCCAs) (45 and 55 bile duct margins, respectively). The diagnosis was classified into three categories: negative, borderline, or positive. FSD in the epithelial layer, subepithelial layer, and total layer was compared with corresponding PSD postoperatively. Then, association between FSD and local recurrence was analyzed. The concordance rate between FSD and PSD was investigated at the margin and patient levels, but survival analysis was performed solely at the patient level.
Analysis of 100 duct margins revealed that original concordance rate between FSD and PSD was 68.0% in the total layer, 69.0% in the epithelial layer, and 98.0% in the subepithelial layer. The extent of remaining biliary epithelium was comparable between FSD and PSD, and more than half of the margins lost > 50% of the entire epithelium, suggesting low quality of the samples. In FSD, the rate of negative margins decreased and that of borderline and positive margins increased according to the extent of the remaining epithelium, suggesting proportional sensitivity to the remaining rate and intrinsic difficulty in the assessment of the epithelial layer. Diagnostic discordance between FSD and PSD was observed in 31 epithelial layers and two subepithelial layers. Although the discordance rate in the epithelial layer was somewhat higher in pCCA than dCCA, there was no significant difference between them in the epithelial layer and subepithelial layer. Alteration from borderline to negative was the most frequent (20 of the 31 epithelial layers). Less frequently, alterations from negative to borderline (4 margins) and positive to borderline (4 margins) were observed in the epithelial layer. Although some authors reported no correlation between positive margins and postoperative local recurrence, in the present study patients with positive margin in the total and epithelial layers by FSD demonstrated a significantly worse local recurrence-free survival (RFS) compared with patients with borderline and negative margins. On the other hand, patients with borderline and negative margins in the total and epithelial layers by FSD revealed comparable local RFS. Patients with borderline and negative margins in the epithelial layer by PSD also revealed comparable local RFS. These results suggested that epithelial borderline might be regarded substantially as negative in such institutions as having well-experienced pathologists. However, if the first margin is borderline and additional margin can be safely obtained, additional ductal resection will be desirable to achieve negative margin, because it is quite likely that some borderline margins may ultimately turn out to be positive in a larger series with more diverse pathologist and the local recurrence is very high in positive margins. When classifying the status of the epithelial layer either as negative or positive, concordance rates between FSD and PSD in the total, epithelial, and subepithelial layers were 95.0%, 93.0%, and 98.0%, respectively. These results suggest that FSD is a reliable method to evaluate margin status of the bile duct intraoperatively.
FSD of the bile duct margin was reliable enough to provide useful information for deciding the extent of resection of eCCA regardless of technical limitations in sample preparation. In contrast to the previous reports, positive margins in the epithelial layer was significantly associated with local recurrence, while the borderline margins demonstrated a similar local recurrence rate to that of negative margins. Although negative margin is desirable, epithelial borderline lesions could be regarded substantially as negative in such institutions as with well-experienced pathologists. These findings would aid surgeons to determine the resection range of the bile duct and better manage the patients with eCCA.
Intraoperative FSD of the bile duct margins has traditionally been used to guide the extent of operative resection, but the usefulness of FSD has been controversial until now. In the present study, we clearly demonstrated that FSD was reliable enough for pathological diagnosis by comparing FSD and PSD and based on the results of survival analysis. In addition, in contrast to some previous reports, we demonstrated that positive FSD in the epithelial layer was significantly associated with local recurrence and that borderline FSD in the epithelial layer could be substantially regarded as negative. Our results may be partly due to a relatively large number of eCCA cases. This study also highlighted the need for precise and detailed histopathological diagnosis. In this respect, the future challenge is more objective differential diagnosis of BilIN-1, 2, and 3 by FSD. Development of morphometric analysis, special staining procedure, immunohistochemistry, and molecular diagnostics which can be available over a short time of intraoperative FSD are awaited. It will be also necessary to develop the training program of pathologists who can make a correct diagnosis of bile duct margin by intraoperative FSD.