Background and aims: Identifying the invasive depth of cancers less than 10 mm in diameter remains a challenge. This study examines the clinicopathological characteristics of colorectal cancers less than 10 mm in diameter and invading submucosal layer (SM)3 and below, which require surgery and must never be treated by endoscopic mucosal resection.
Methods: We studied 54 cases of colorectal cancer less than 10 mm in diameter and invading the submucosa and deeper tissues, by dividing them into two groups: those invading SM1 and SM2 versus those invading SM3 and below. We investigated the clinicopathological characteristics of cancers invading SM3 and below by comparing them with cancers invading SM1 and SM2. Similarly, 38 cases, whose endoscopic findings could be analyzed, were selected and examined.
Results: In cases invading SM3 and below, the rates of moderately to poorly differentiated adenocarcinoma, lymphatic and venous permeation and lymph node metastasis were significantly higher than those invading SM1 and SM2. Among cases invading SM3 and below, the presence of endoscopic findings-including white spots of the protruded type, and fullness, white spots, hardness and protruded lesions in the depressed area of the depressed type-was significantly higher than among those invading SM1 and SM2.
Conclusion: Colorectal cancers less than 10 mm in diameter and invading SM3 and below have high malignant potential. Cancers of this invasive depth can be identified by looking for characteristics such as white spots, fullness, hardness and protruded lesions in the depressed area. Careful endoscopic observation for these signs aids in determining the appropriate treatment.