On this study, " Diminutive Polyp " means any raised or protruded mucosa (5 mm or less in its diameter). Such a lesion is impossible to make the differential diagnosis from its gross appearance.
The dissected colon specimens fixed with formalin were stained with Carazzi-hematoxylin and these 277 diminutive polyps were studied dissecting microscopically. Moreover they could be classified as four types. The pit of normal mucosa usually shows circular, similar and regular. Four types are as follows.
(1) Circular Type····Pit shows circular and enlargement of the normal mucosa.
(2) Papillary Type····Pit looks like star. Owing to papillary infoldings, pit becomes small or narrow.
(3) Tubular Type····Various pit can be found from circular to oval and irregular.
(4) Sulcus Type····Pit can not seen, but sulcus formation (cerebral gyrous like) can be found. Histologically, the circular type was only elongation and enlargement with normal Lieber-Kiihn crypt, papillary type was typical hyperplastic polyp, tubular type was tubular adenomatous polyp and sulcus type was papillary adenomatous polyp.