Abstract
The term "Serrated adenoma (SA)" was proposed by Longacre et al in 1990 to emphasize its neoplastic character and to distinguish from MHAP. We studied histological and endoscopical macroscopic features of SA which is fit for the pathological diagnotic criteria of Longacre et al. Ninty-three SAs excised from 90 patients and 11 MHAPs excised from 11 patients by colonoscopy during the period between 1977 and 95, were studied. As control, 170 hyperplastic polyps (HPs) excised from 151 patients in the same period were used. The sizes of tumors in SA (average; 10.3 mm) and MHAP (average ; 8.2 mm) were larger than those of HP (average ; 5.4 mm). Endoscopically, HP tended to show smooth surface with whitish mucosa and SA tended to show lobular and/or granular surface and reddish mucosa. Histologically, SA could be classified into two types of growth pattern, mono-existing type purely composed of adenoma, and co-existing type composed of admixed HP. Proliferating cells in SA frequently moved from the base of the crypt to the upper portion by Ki-67 (MIB-1) stain. The index of MIB-1 was relatively high on the base of the crypt with mild or moderate atypia. On the other hand, the labeling index of MIB-1 was equal between the upper portion and lower portion of the crypt in SA with high grade atypia. This was also seen in traditional tubular adenoma. The results obtained in this study suggest that SA has a neoplastic character similar to tubular adenoma, and should be treated in the same way as tubular adenoma.
