Should laterally spreading tumors granular type be resected en bloc in endoscopic resections?

Currently, granular-type laterally spreading tumors (LST-G) have been classified into uniform [LST-G (UNI)] and nodular mixed [LST-G (MIX)] subtypes. However, the progression pattern of each subtype has not been evaluated in detail. The present study was designed to assign adequate treatment strategies to each LST-G subtype, based on the progression pattern.

This retrospective study included 457 consecutive patients with 482 LST-Gs that had been removed endoscopically or surgically in a tertiary cancer center between September 2002 and December 2011. We classified the tumors as LST-G (UNI) or LST-G (MIX) subtypes. We analyzed clinicopathological characteristics and submucosal invasion rates for both subtypes, and we determined the incidence of submucosal invasions associated with the largest nodules for each subtype.

We evaluated the histopathological data from 136 LST-G (UNI) and 316 LST-G (MIX) lesions with diameters of 10-19 mm (14%), 20-29 mm (26%), 30-39 mm (25%), or >40 mm (35%). Submucosal invasions were observed in 3 (1.8%) LST-G (UNI) and 49 (15.5%) LST-G (MIX) lesions. In LST-G (MIX) lesions, the submucosal invasion incidences (within a tumor-size category) were as follows: 5.8% (10-19 mm), 11.1% (20-29 mm), 14.7% (30-39 mm), and 19.1% (>40 mm), respectively. In LST-G (MIX) lesions that showed submucosal invasions, the invasive cancers were located under the largest nodule (69%; 34/49), outside the largest nodule (25%; 12/49), or in both sites (6%; 3/49).

Our results indicated that, for LST-G (UNI) lesions, piecemeal resections would be acceptable due to the low risk of submucosal invasion. For LST-G (MIX) lesions, particularly those with diameters ≥20 mm, en bloc removal in an endoscopic resection is preferable for sufficient histological evaluation.