Pathologic T1 subclassification of ampullary carcinoma with perisphincteric or duodenal submucosal invasion: Is it T1b?

Context: In ampullary carcinoma staging, T1 is defined as a tumor limited to the ampulla of Vater or the sphincter of Oddi, and T2 is defined as invasion into the duodenal wall. However, the definition of duodenal wall invasion is vague. Ampullary carcinoma that invades beyond the sphincteric of Oddi (perisphincteric invasion) or into the duodenal submucosa could be considered pT1b because submucosal invasion is classified as pT1b in gastrointestinal tract tumors. However, there are no data regarding T subclassifications for ampullary carcinoma with perisphincteric or duodenal submucosa invasion.
Objective: To determine the T subclassification of ampullary carcinoma that invades into perisphincteric or duodenal submucosa.
Design: Pathologically proven ampullary carcinomas with T1 or T2 were reviewed (n = 105). We reclassified tumors as pT1a that were limited to within the sphincter of Oddi (n = 40; 38%), as pT1b for tumors that invaded beyond the sphincter of Oddi or into the duodenal submucosa (n = 25; 24%), and as pT2 for tumors that invaded into duodenal proper muscle (n = 40; 38%).
Results: Lymph node metastasis and recurrence were absent in ampullary carcinoma with pT1a, whereas nodal metastasis were noted in 24% (6 of 25) and 40% (16 of 40) of the ampullary carcinomas with pT1b and pT2, respectively. Tumor recurrence/metastasis rate of ampullary carcinoma with pT1b and pT2 was 44% (11 of 25) and 40% (16 of 40), respectively. The 5-year disease-free-survival rates from ampullary carcinoma with pT1a, pT1b, and pT2 were 95% (38 of 40), 56% (14 of 25), and 58% (23 of 40), respectively (P = .003). The 5-year overall survival from ampullary carcinoma with pT1a, pT1b, and pT2 was 98% (39 of 40), 72% (18 of 25), and 60% (24 of 40), respectively.
Conclusions: The clinicopathologic outcome of ampullary carcinoma with a pT1b subclassification was worse than it was for T1a and approached the outcome for pT2.