4514 Characteristics of large flat colorectal tumors (so-called laterally spreading tumors).

Abstract

Some flat adenomas spread extensively and circumferentially along the colonic wall although being very short in height compared with the large diameter of more than 10 mm. These large flat adenomas or so-called laterally spreading tumors (LSTs) are sometimes malignant, but not so advanced compared with their large diameter. Despite the large diameter, LSTs are often difficult to find, because they are extremely short and almost normal in color. The keys to detect them are a minimal color change, which is usually faintly red and a slight irregularity of the intestinal wall or interruption of the mucosal capillary network pattern. Dyespraying (usually 0.2-0.4% indigo carmine) helps clarify the margin and the extent of the tumor. [Materials and Methods] From April 1985 to August 1999, 522 LSTs were resected endoscopically and/or surgically. These lesions were classified into granular and non-granular. Endoscopic features of submucosal involvement Duke's A carcinomas in LSTs were analyzed. [Results] Rate of submucosal invasion in LST was 9.2% (48 out of 522). This rate was 9.6% (25 out of 261) in granular type and 8.8% (23 out of 261) in non-granular type. Granular LST consists of many small aggregated nodules. But sometimes it has the remarkable protruding part. Rate of submucosal invasion in Granular LST with the remarkable protruding part was 22.0% (24 out of 109). On the other hand, 68.8% of these 24 submucosal involvement Duke's A carcinomas became invasive in the protruding part exactly. Non-granular LST does not have nodules. Sometimes it has the ill-defined pseudodepression which appears after dye-spraying. This is different from the depressed carcinoma, which has the well-demarcated depression. Rate of submucosal invasion in non-granular LST with the pseudodepression was 18.0% (11 out of 61). All of these 11 submucosal involvement Duke's A carcinomas became invasive in the depressed part. [Conclusion] LSTs are good indication for EMR or endoscopic piecemeal mucosal resection (EPMR). Lesions up to 25 mm in diameter can be removed en bloc by EMR technique. Those over 25 mm would be treated with EPMR method. However, if the part of LST shows coarse protruding structure or psudodepression, the lesion is suspected to be deeply invasive, and therefore should be treated surgically. It is very important to recognize these significant laterally spreading colorectal tumors by careful observation and dye-spraying method.