Does ampullary adenoma size predict invasion on EUS? Does invasion on EUS predict presence of malignancy?

Background and study aims: It is common practice to perform ampullectomy without endoscopic ultrasound (EUS) for ampullary lesions < 1 cm but no data exists to support it. No studies have explored whether EUS findings of invasion correlate with malignancy or high-grade dysplasia (HGD) on pathology. We explored the association between adenoma size, pathology results, and invasion on EUS.  Patients and methods: This was a single-center retrospective cohort study at a large tertiary care academic hospital. Chart review was performed for 161 patients with benign ampullary lesions on endoscopic biopsy (identified by pathology records). The primary outcomes were mean size (mm) of adenomas and pathology findings with and without intraductal and/or duodenal wall invasion on EUS.  Results: Invasion was identified by EUS in 41 (34.1 %) of 120 patients who underwent EUS. The mean size of the lesion in these patients was 20.9 mm (± 11.6 mm) compared to 13.9 mm (± 11.3 mm, P = 0.0001) in patients without invasion. A receiver operating characteristic (ROC) curve (AUC 0.73, 95 % CI 0.63 - 0.83) revealed 100 % sensitivity for absence of invasion on EUS in lesions less than 6.5 mm. Invasion on EUS had sensitivity of 63.0 % (95 % CI 47.0 % - 77.0 %) and specificity 88.0 % (95 % CI 78.0 % - 95.0 %) for presence of malignancy, HGD or invasion on pathology. Conclusions: EUS should be considered for ampullary lesions > 6.5 mm. This study provides evidence to support the practice of ampullectomy without EUS for smaller adenomas. EUS evidence of invasion is highly specific for pathologic malignancy, HGD, or invasion (which preclude endoscopic ampullectomy).