| [ Summary ] |
According to macroscopic morphology, colorectal tumors (adenoma and early carcinoma) are classified into the protruded type (0-I) and the superficial type (0-II). Superficial types are further classified into the superficial elevated type (0-IIa) and the depressed type (0-IIc). In addition, laterally spreading tumors (LST) have been identified in lesions larger than 10 mm in diameter and extending circumferentially rather than vertically. They are classified into two subtypes : granular (LST-G) and non granular (LST-NG). The histological and genetic features of each macroscopic type of colorectal tumor (protruded type, superficial elevated type, superficial depressed type and LST-G, LST-NG) were analysed. Genetically, 0-I type tumors may be divided into two groups, adenoma and adenocarcinoma. They may have adenomal components, or have adenocarcinoma appearance without adenomal components. The former revealed high incident K-ras mutation and focal p53 expression and resembled LST-G, the latter had low incident K-ras mutation and diffuse p53 expression and resembled 0-IIc. LST-NG of small size (10 ≤ <20 mm) may simulate 0-IIa tumors in terms of low incident K-ras mutation and diffuse p53 expression, as well as loss of E-cadherin membranous expression. It is important to understand that each macroscopic type of colorectal tumor has distinctive histological and genetic features. |