Endoscopic submucosal dissection (ESD) is a well-established technique for en bloc resection of large premalignant colorectal lesions, providing high R0 resection rates and low recurrence (1). Its use has expanded to include early-stage colorectal cancer (CRC) (2-5). However, the increasing adoption of ESD has led to finding of incidental high-risk histopathological features, for which post-ESD management, whether conservative or surgical, remains less clearly defined with variance among guidelines. The American Gastroenterological Association and the European Society of Gastrointestinal Endoscopy recommend ESD for lesions with high suspicion of limited submucosal invasion (1,6). For non-curative ESD, surgery is generally advised unless surgical risk is prohibitive, in which case close endoscopic and radiologic surveillance is an alternative. Positive vertical margin and lymphovascular invasion are particularly associated with residual tumor and nodal involvement (2,7). The aim of this study was to present our data on incidental CRC findings after ESD and to evaluate subsequent surveillance outcomes.

We conducted a retrospective, single-centre study including consecutive patients who underwent ESD for suspected premalignant colorectal lesions with unexpected diagnosis of colorectal cancer (CRC) on final histopathology. Between 2018 and 2025, a total of 241 colorectal lesions were resected en bloc with ESD. Clinical, endoscopic, histopathological, and follow-up data were collected and analysed, focusing on curative resection status, subsequent management, and oncological outcomes.

Of the 241 lesions, 11 (4.5%) were diagnosed as submucosal invasive carcinoma (SMIC). Lesions were located within the rectum (3/11, 27.3%) and colon (8/11, 72.7%). R0 curative resection was achieved in 1 case (9.1%), R0 non-curative in 2 (18.2%), and R1 resection with positive vertical margins in 8 cases (72.7%). Among the non-curative R0 resections, one patient underwent radical surgery with no residual malignancy identified; none of the R0 cases showed local recurrence or distant disease during follow-up (median follow-up time was 39 months (IQR 27-42.5, range 15-46)).

Of the 8 R1 resections, 6 (75%) underwent surgery and 2 (25%) were managed conservatively. Four (66.7%) of the surgical cases showed deeply invasive (≥1000 µm) submucosal carcinoma, while 2 (33.3%) had no residual malignancy. Overall, 50% of R1 resections had no recurrence at median follow-up of 13 months (IQR 9.5-15, range 5-17).

Among the 11 patients with high-risk features, 7 (63.6%) achieved curative resection with ESD alone, showing no residual disease or recurrence at follow-up despite 8 having had R1 resection. Total median follow-up time was 15 months (IQR 10–17, range 5–46).

All 4 cases with residual cancer after surgery (36.4%) showed surface features JNET 2B, variably located in the sigmoid (25%), transverse (25%), ascending colon (25%), and rectum (25%). These included 2 Paris 0-Is (50%), 1 LST-G-M (25%), and 1 LST-NG-FE (25%); all were R1 resections, and all presented with muscle-retraction during ESD. Biopsies pre-ESD were only available in two out of four patients: only low-grade dysplasia in one and focal high-grade dysplasia the other.

Incidental colorectal cancer diagnosed after ESD is infrequent but clinically relevant. Most cases, including some with R1 resection, required no additional treatment, highlighting that selected patients with limited submucosal invasion and favourable histology may potentially be safely managed conservatively, especially if elderly or comorbid. Nevertheless, achieving R0 resection remains essential to minimise the risk of residual disease or recurrence. Radical surgery offered a curative option in patients with high risk findings after ESD. Future prospective studies are needed to validate these findings and establish evidence-based recommendations for post-ESD management.