Ultrastructure of colon pit pattern classification

Abstract

Objective To explore morphological changes in evolution of colorectal pit patterns and their relation with polyp development by observing the ultrastructure of colorectal polyps. Methods Analyses were based on data from 50 subjects with colorectal polyps diagnosed with magnifying colonoscopy. Colonoscbpy combined with endoscopic lesions staining was employed to determine the pit pattern of colorectal lesions, according to Kudo classification. Colorectal lesions were removed through endoscopy or surgery. All samples were analyzed with histopathology, scanning and transmission electron microscopy. Results The pit phttern or 50 samples included 10 cases of type Ⅰ , 8 cases of type Ⅱ, 15 cases of type Ⅲ, 9 cases of type Ⅳ, 5 cases of type Ⅴ and 3 cases of mixed-type. The positive predictive rate and the accuracy rate of differential diagnosis of neoplastic polyps, verified with histological diagnosis, were 86% and 94% , respectively. Under scanning electron microscopy, crypt morphology in type Ⅰ and type Ⅱ exhibited regular round hole shape, with epithelial cells in uniform size, abundant absorptive cells with rich microvilli and goblet cells. Crypt in type Ⅲ, type Ⅳ and type Ⅴ appeared gradual deformation accompanied by increasingly atypical hyperplasia in the epithelial cells and heterotypic tissues. Transmission electron microscopy revealed epithelium of type Ⅰ and type Ⅱ arranged regularly and connected closely, with neat microvilli at the top of cells, affluent mitochondria and endoplasmic reticulum in the cytoplasm, oval nuclear at the base, and smooth and continuous basement membrane. While the epithelium of type Ⅲ, type Ⅳ and type Ⅴ was characterized by sparse and irregular villi, swelling mitochondria and expanded endoplasmic reticulum, lysosomes of increased number, heterotypic nuclear and mitotic nuclear, and broken and disappearing substrate. Conclusion Morphological changes in pit pattern of colorectal polyps is affected by surface structure of glandular epithelial cells, the proportion and composition of the crypt surface cellsn. Ultrastructural changes in epithelial cells are the material basis of morphological changes in pit pattern and polyp development. Key words: Scanning electron microscopy; Transmission electron microscopy; Pit pattern