大肠侧向发育型肿瘤(Laterally SpreadingTumor,LST)指起源于大肠粘膜的一类平坦隆起型病变。这类病变极少向肠壁深层垂直侵犯,而主要沿粘膜表面呈侧向浅表扩散,故称之为侧向发育型肿瘤。大肠的Serrated腺瘤指大肠的一类特殊病理形态的腺瘤,其成瘤上皮成分有明显增生,使腺管或绒毛呈现锯齿状外观,类似于增生性息肉样改变,或腺瘤成分与增生性息肉成分同时存在。以上两类肿瘤均为具有特殊形态的大肠少见肿瘤,同一病变同时具有 Lateral Spreading Tumor (LST) refers to a class of flat bulging lesions originating from the large intestine mucosa. These lesions rarely invade the deeper vertical wall of the intestine, but are mainly distributed laterally along the surface of the mucosa, so they are called lateral developmental tumors. The Serrated adenoma of the large intestine refers to a group of adenomas of the large intestine with a special pathological morphology. The tumor-epithelial component has a marked hyperplasia, a serrated appearance of the ducts or villi, similar to hyperplastic polypoid changes, or adenoma components and hyperplasia. The polyp component exists at the same time. The above two types of tumors are rare tumors of the large intestine with a special shape, and the same lesion also has