The Incidence and Significance of Villous Change in Adenomatous Polyps

Abstract

A retrospective review of 108 colonic adenomatous polyps revealed focal villous change in 6% of solitary lesions, 15% of polyps with coexisting adenocarcinoma, 33% of those with coexisting villous adenoma, and 64% of polyps with carcinomatous transformation. However, a subsequent prospective analysis of 67 colonic polypoid lesions, using a dissecting microscope and more sections, indicated that the incidence of focal villous change had been underestimated. This feature was found in 35% of solitary adenomatous polyps and appeared to be directly related to the size of the polyps, reaching 75% in lesions larger than 1 cm. in diameter. The dissecting microscopic interpretations provided the correct estimate of a villous pattern in 96% of cases. Although morphologically the adenomatous polyp with focal villous change appears to represent an intermediate form between the pure adenomatous polyp and the villous adenoma, evidence for obligatory transformation and increased malignant potential of this form is inconclusive. The difficulty that may be encountered in the interpretation of a villous area in a small biopsy is discussed.