Distribution of intraductal lesions in small invasive ductal carcinoma of the pancreas.

AIMS: To investigate the distribution of intraductal lesions in small invasive ductal carcinoma (IDC) of the pancreas.

METHODS

In 21 cases with IDCs microscopically < or = 20 mm in diameter, the intraductal lesions around a mass were studied histologically and mapped according to the pancreatic intraepithelial neoplasia (PanIN) classification.

RESULTS

PanIN-3, PanIN-2, PanIN-1B and PanIN-1A were found in 17, 10, 20 and 21 of 21 cases, respectively, and were divided into lesions in adjacent and distal areas, respectively defined as within and beyond 10 mm from the mass as follows: 100% (17/17), 100% (10/10), 95.0% (19/20) and 90.5% (19/21) in the former, while 23.5% (4/17), 50.0% (5/10), 90.0% (18/20) and 95.2% (20/21) in the latter. PanIN-3 lesions were predominantly found in the area adjacent to the mass. In some cases, significant PanIN-3 appeared to show a consecutive geographic extension around the mass via the main pancreatic duct (MPD). The distance of PanIN-3 spread was within 25 (mean 10.5) mm from the mass edge. PanIN-2 lesions were found in the area adjacent to the mass and discontinuous with the mass or PanIN-3 lesions. PanIN-1B and PanIN-1A tended mainly to exist sporadically throughout the entire pancreas. In the MPD, PanIN-3 was found in 14 (82.4%) of 17 cases and in 36 (32.1%) of 112 lesions, which was most frequent in intraductal lesions.

CONCLUSIONS

PanIN-3 lesions might be an intraductal extension of the main tumor. The resection margin of 25 mm, at least longer than 11 mm, from the mass edge will be necessary.