Background: The American Joint Committee on Cancer (AJCC) T classification system for cholangiocarcinoma does not take into account the unique pathologic features of the bile duct. As such, the current AJCC T classification for distal cholangiocarcinoma may be inaccurate. Methods: A total of 147 patients with distal cholangiocarcinoma were identified from a single institution database. The prognostic importance of depth of tumor invasion relative to the AJCC T classification system was assessed. Results: The AJCC T classification was T1 (n = 11, 7.5%), T2 (n = 6, 4.1%), T3 (n = 73, 49.7%), or T4 (n = 57, 38.8%). When cases were analyzed according to depth of tumor invasion, most lesions were ≥5 mm (<5 mm, 9.5%; range, 5-12, 51.0%; >12 mm, 39.5%). The AJCC T classification was not associated with survival outcome (median survival, T1, 40.1 months; T2, 14.8 months; T3, 16.5 months; T4, 20.2 months; P = .17). In contrast, depth of tumor invasion was associated with a worse outcome as tumor depth increased (median survival, <5 mm, not reached; range, 5-12, 28.9 months; >12 mm, 12.9 months; P = .001). On multivariate analyses, tumor depth remained the factor most associated with outcome (<5 mm; hazard ratio [HR] = referent vs 5-12 mm; HR = 3.8 vs >12 mm; HR = 6.7 mm; P = .001). Conclusion: The AJCC T classification for distal cholangiocarcinoma does not accurately predict prognosis. Depth of the bile duct carcinoma invasion is a better alternative method to determine prognosis and should be incorporated into the pathologic assessment of resected distal cholangiocarcinoma.
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