Reappraisal of classification of distal cholangiocarcinoma based on tumour depth

Abstract

ITT is an accurate approach for depth assessment in DCC. The four-tier ITT classification with cut-off points of 1, 5 and 10 mm seems to be a better T system than those in the seventh and eighth editions of the AJCC classification.

Proposal for a new classification for perihilar cholangiocarcinoma based on tumour depth

“…However, specific cut‐off points for ITT in perihilar tumours were not sought. Interestingly, the cut‐off points of 1, 5 and 8 mm reported in the present study are similar to those in other studies of distal or extrahepatic cholangiocarcinoma. A C1 tumour (ITT less than 1 mm) was highly associated with intraductal growth type, well differentiated histological grade, rare microscopic neurovascular invasion and absence of nodal metastasis ( Table ); all of these factors are well known positive prognostic indicators.…”

“…This revision relies on two findings by Hong and colleagues, that the obscure outer layer of the bile duct leads to an uncertain T assignment and the depth‐based T system was better able to stratify than the layer‐based system. The present authors previously analysed patients with distal cholangiocarcinoma, confirming the satisfactory prognostic discrimination of this depth‐based approach despite two problems associated with depth measurement: lack of evidence of reliability and measurability susceptible to the direction of section of resected specimens. Recently, a single study demonstrated the prognostic value of tumour depth in perihilar cholangiocarcinoma, but failed to propose a T system using tumour depth.…”

“…This heterogeneity required the predefinition of measurement methods according to the gross tumour morphology, an approach that is frequently applied for tumours such as cutaneous melanoma and early‐stage colorectal cancer. To date, two measurement methods have been reported for depth assessment in cholangiocarcinoma: DOI and ITT. It was reported previously that the measurability of DOI depended on tumour morphology, size and direction of sectioning of the resected specimen, but the measurability of ITT did not.…”

“…To date, two measurement methods have been reported for depth assessment in cholangiocarcinoma: DOI and ITT. It was reported previously that the measurability of DOI depended on tumour morphology, size and direction of sectioning of the resected specimen, but the measurability of ITT did not. Although de Jong and colleagues consistently used DOI for depth assessment, the figures reported in their study of perihilar tumours demonstrated that they measured the distance from the top of the tumour to the advancing tumour margin, that is the ITT.…”

“…Invasive tumour thickness (ITT) was defined as the vertical distance from the top of the tumour to the deepest invasive cells ( Fig . ), as reported previously. Microscopic perineural, lymphatic and venous invasion were not considered for this measurement.…”