The T category of distal extrahepatic bile duct carcinoma (DBDC) is based on invasion depth from the basal lamina to the deepest infiltrating tumor cells. Recently, invasive tumor thickness (ITT) was proposed, defined as maximal vertical distance of invasive tumor components regardless of the basal lamina. We compared the predictive value of T category, and ITT grading in 424 surgically resected DBDCs. DBDCs were categorized as 6 Tis (1.4%), 134 T1 (<5 mm; 31.6%), 204 T2 (5 to 12 mm; 48.1%), and 80 T3 (>12 mm; 18.9%). With ITT, there were 6 G0 (no invasion; 1.4%), 3 G1 (<1 mm; 0.7%), 90 G2 (≥1 and <5 mm; 21.2%), 188 G3 (≥5 and <10 mm; 44.4%), and 137 G4 (≥10 mm; 32.3%). The 5-year survival rates of T1, T2, and T3 were 58.9%, 44.2%, and 18.2%, and those of ITT G1, G2, G3, and G4 were 33.3%, 54.1%, 51.6%, and 26.7%, respectively. The T category discriminated patient survival by overall (P<0.001) and pairwise (T1 vs. T2, P=0.007; T2 vs. T3, P<0.001) comparisons. ITT grading distinguished survival by overall and between G3-G4 (both P<0.001), with no survival differences observed between G1-G2 and G2-G3 comparisons. The T category more accurately discriminated patient survival than ITT grading. To determine the T category for DBDCs, (1) longitudinal sectioning on gross examination, especially for DBDCs with large papillary or nodular growth patterns; (2) evaluation of serial sections or alternative hematoxylin and eosin slides; (3) use of a straight or curved baseline depending on the shape of the peritumoral normal bile duct wall and/or the basal lamina of the peritumoral normal biliary epithelia/biliary intraepithelial neoplasias are recommended.

远端肝外胆管癌（DBDC）的T分类是根据从基底层到最深浸润肿瘤细胞的浸润深度。最近，提出了侵袭性肿瘤厚度（ITT），定义为侵袭性肿瘤成分的最大垂直距离，与基底层无关。我们比较了 424 例手术切除的 DBDC 的 T 类别和 ITT 分级的预测价值。DBDC 分为 6 Tis (1.4%)、134 T1 (<5 mm; 31.6%)、204 T2 (5 至 12 mm; 48.1%) 和 80 T3 (>12 mm; 18.9%)。ITT 中，有 6 个 G0（无侵犯；1.4%）、3 个 G1（<1 mm；0.7%）、90 个 G2（≥1 且 <5 mm；21.2%）、188 个 G3（≥5 且 <10 mm；21.2%）。 44.4%）和 137 G4（≥10 毫米；32.3%）。T1、T2、T3组5年生存率分别为58.9%、44.2%、18.2%，ITT G1、G2、G3、G4组5年生存率分别为33.3%、54.1%、51.6%、26.7%。分别。T 类别通过总体比较（P <0.001）和成对比较（T1 与 T2，P = 0.007；T2 与 T3，P <0.001）比较来区分患者生存率。ITT 分级按总体生存率和 G3-G4 之间的生存率进行区分（均P <0.001），在 G1-G2 和 G2-G3 比较之间未观察到生存率差异。T 类别比 ITT 分级更准确地区分患者的生存情况。为了确定 DBDC 的 T 类别，（1）肉眼检查纵向切片，特别是对于具有大乳头状或结节状生长模式的 DBDC；(2)连续切片或替代苏木精和曙红玻片的评估；(3) 建议根据肿瘤周围正常胆管壁和/或肿瘤周围正常胆管上皮/胆管上皮内瘤变的基底层的形状使用直的或弯曲的基线。