Objectives: Although sporadic nonampullary duodenal adenoma (SNDA) is regarded as a precancerous lesion, its natural course is uncertain. The aim of this study was to evaluate the risk of development of adenocarcinoma in SNDA lesions initially diagnosed as showing low-grade dysplasia (LGD; category 3) or high-grade dysplasia (HGD; category 4.1).
Methods: We analyzed 68 SNDAs, diagnosed based on initial and subsequent biopsies, in 66 consecutive patients. Of these, 46 (43 LGD lesions, 3 HGD lesions) were followed up for ≥6 months without treatment (mean 27.7±16.9 months; range 6-72 months), including 8 lesions that were eventually resected during follow-up. Sixteen lesions (eight LGD lesions, eight HGD lesions) were resected immediately, either endoscopically or surgically, and six lesions were excluded because of a short follow-up (<6 months). The histopathological diagnoses and macroscopic changes were evaluated.
Results: Among the 43 LGD lesions followed up for ≥6 months, 34 (79.1%) showed no histopathological changes during follow-up, whereas the remaining 9 (20.9%) showed progression to HGD, including 2 (4.7%) that progressed eventually to noninvasive carcinoma (category 4.2). Macroscopically, 76.7% (33 of 43) of the LGD lesions showed no notable changes in size, 16.3% (7 of 43) became undetectable, 4.7% (2 of 43) reduced in size, and 2.3% (1 of 43) became larger in size. In contrast, all the three HGD lesions that were followed up for ≥6 months remained unchanged histologically, based on biopsy, and showed no notable macroscopic changes, although one of these HGD lesions resected endoscopically revealed evidence of noninvasive carcinoma. Although we diagnosed all lesions as HGD from biopsy samples, a high percentage of cancers (54.5%, 6 of 11) were diagnosed from resected specimens. A multivariate analysis identified HGD diagnosed at first biopsy and a lesion diameter of ≥20 mm as being significantly predictive of progression to adenocarcinoma.
Conclusions: LGD lesions show a low risk of progression to adenocarcinoma, but some risk of progression to HGD, which warrants careful follow-up biopsy. However, HGD lesions and large SNDAs≥20 mm in diameter show a high risk of progression to adenocarcinoma. Therefore, they should be treated immediately.