The difference in malignancy between pedunculated and sessile polypoid lesions of the gallbladder.

Surgically resected polypoid lesions of the gallbladder from 97 patients were evaluated to determine both the shape (pedunculated or sessile) and diameter of the polypoid lesions, in association with malignancy. At the time of analysis, the largest polypoid lesion examined was when two or more lesions were detected in one patient because they were histologically the same. Carcinoma was noted in 9 (13%) of the 67 pedunculated lesions and in 10 (33%) of the 30 sessile lesions. The sessile carcinoma was 14 +/- 4 mm (8-20 mm) in maximum diameter, which was not significantly larger than the 8 +/- 4 mm of the benign polyps, but significantly smaller than the 22 +/- 8 mm (14-35 mm) of pedunculated carcinomas (p less than 0.05). Cancer invasion extended beyond the muscular layer in eight cases (80%) of sessile carcinoma, and two of them were 10 mm or less in diameter. On the other hand, cancer invasion was beyond the muscular layer in two cases (22%) of pedunculated carcinoma (p less than 0.05), and these two were 30 mm or more in diameter. Likewise, sessile carcinoma was characterized by both a higher incidence of nodal involvement and poorer prognosis, compared with pedunculated carcinoma. These findings indicate that surgery should be undertaken when sessile polyps are detected by ultrasonography, even though the polyp may be less than 10 mm in diameter. On the other hand, with regard to the pedunculated type, malignancy should be suspected when the polyp is more than 10 mm in diameter.