Histological factors contributing to a high risk of recurrence of submucosal invasive cancer (pT1) of the colon and rectum after endoscopic therapy.

We analyzed the histological high-risk factors for recurrence of submucosal invasive carcinomas (pT1) of the colon and rectum after endoscopic therapy, examining pT1 cancers treated primarily by endoscopic resection within a 23-year period. We compared recurrent and nonrecurrent cancers, evaluating the following "highrisk factors" of the primary lesion: massive invasion, a surgical margin<2 mm but negativity for cancer in the cut end, poorly differentiated adenocarcinoma (PD) (G3), undifferentiated carcinoma (G4), and/or positive angiolymphatic invasion. The following histological factors were defined as predictive of a low risk: minimum invasion, a surgical margin>2 mm, well or moderately differentiated adenocarcinoma (G1, G2), and no evidence of angiolymphatic invasion. We analyzed the records of 37 patients with pT1 cancers, including 15 with high-risk factors who underwent subsequent resection. Local recurrence with or without liver metastases developed in 4 of these 15 patients. The histological type was PD in three (75%) of the four recurrent lesions. All four (100%) lesions showed a desmoplastic response (DR). Only 1 (9%) of the 11 patients without recurrence after subsequent surgery had a lesion with a small component of PD, and only three (27%) lesions showed a mild DR. We concluded that endoscopic therapy is inadequate for pT1 cancers with a histological PD component, and/or a DR in the cancer stroma.