**3.3. Flat intraepithelial neoplasia**

Especially in the stomach, intraepithelial neoplasia is flat and demonstrates endoscopically with only slight, uncharacteristic abnormalities. Frequently flat intraepithelial neoplasia arises in a background of chronic gastritis later in life (beyond the fifth decade). By convention, the intraepithelial neoplasia has to divide into either low grade or high grade.

Microscopically, the main characteristics of intraepithelial neoplasia consider cytology and architecture (like in adenoma):

Low-grade intraepithelial neoplasia preserves more or less the normal glandular differentiation, the epithelia show enlarged hyperchromatic nuclei, the nucleoli are not prominent, and cell pleomorphism and cell stratification are limited.

High-grade intraepithelial neoplasia demonstrates with crowding of glands, including budding and branching of some glands. The nucleoli are prominent and often intense eosinophilic.

#### *3.3.1. Clinical significance*

Flat low-grade intraepithelial neoplasia: re-endoscopy to exclude concurrent carcinoma is suggested. The risk of carcinoma is low (about 25%). Re-endoscopy twice a year and annual after two negative endoscopies is suggested.

Flat high-grade intraepithelial neoplasia: the risk of accompanied carcinoma is high (about 85%). An excision of the whole lesion/region is necessary [2, 11].

#### *3.3.2. Vienna classification of gastrointestinal epithelial neoplasia*

Geographic differences in interpretation of gastric epithelial tumours exist (generally between Western pathologists and Japanese pathologists). The Vienna classification of (pre-)cancerous lesions of the GI-tract tries to harmonize both interpretations (**Table 5**).


**Table 5.** Vienna classification of gastrointestinal epithelial neoplasia.
