11^th Global Gastroenterologists Meeting

Background & Aim: Laterally spreading tumors (LSTs) are generally defined as superficial lesions≧10 mm in diameter that extend laterally rather than vertically along the colonic wall. They are divided into granular type and non-granular type; the former is further divided into homogenous (LST-G(H)) and mixed nodular (LST-G(M)) and the latter is subdivided into flat-elevated (LST-NG(F)) and pseudo-depressed(LST-NG(P)). It seems that the biological behavior is different among these four subtypes. The goal of this study is to clarify the endoscopic and pathological characteristics of each subtype and establish therapeutic strategies for LSTs based on the sub-classification.

 

Methods: We investigated consecutive 380 lesions of LST in 349 patients which were treated in our hospital between April 2010 and June 2014. The location, maximum diameter, invasive rate and the surface pit pattern were evaluated.

 

Results: The LST patients included 186 males and 163 females and the average age was 68.3 year old. The therapeutic method was EMR in 158 (piecemeal EMR: 41), ESD in 207 and surgery in 15. The most affected site by each subtype was the cecum LST-G(H), the rectum in LST-G(M), and transverse colon in LST-NG subtypes. The mean size was 29.5 mm in LST-G(H), 38.1 mm in LST-G(M), 20.5 mm in LST-NG(F), and 24.2 mm in LST-NG(P). The invasive rate in each subtype was 0.8%, 18.5%, 5.3%, and 15.9%, respectively. It seems that piecemeal resection is acceptable for LST-G(H) as the possibility of its being an invasive cancer is extremely low. Mixed granular type can also be treated with a snare provided that the nodular part cannot cut as piecemeal. It is sometimes difficult to predict in which part the flat-elevated type is invading. In such cases, the pit pattern observation is useful; when the pit pattern is type III L or IV, the corresponding part is not invasive but the area with type V pit pattern should not cut into pieces as this part is supposed to be invasive. 

 

Conclusion: The biological behavior is difficult among the four subtypes of LSTs. We should predict the histology precisely and determine the therapeutic strategy based on the subtype and also the pit pattern of the lesion surface.