Characteristics of small early colorectal cancer in the non-pedunculated lesions and its relationship with the depth of invasion

BACKGROUND: Colorectal cancer (CRC) exhibits high morbidity and mortality globally among malignant tumors. Early diagnosis and treatment can improve prognosis. Previously, tumor size was considered correlated with colorectal cancer invasion. However, whether small CRCs exhibit lower aggressiveness remains uncertain. To investigate the endoscopic features and risk factors for deep submucosal invasion in early, non-pedunculated CRCs with a diameter < 2 cm, and to establish a preliminary nomogram to inform clinical diagnosis and treatment. METHODS: We retrospectively analyzed clinical, endoscopic, and pathological data from 289 patients who underwent endoscopic submucosal dissection (ESD) or surgical resection for non-pedunculated polyps or early-stage colorectal cancer with a diameter < 2 cm at the Affiliated Hospital of Qingdao University between January 2015 and November 2024. Patients were grouped based on the nature and invasion depth of the lesion. Statistical descriptions were performed for each group, and a preliminary nomogram was constructed to evaluate its predictive value for deep submucosal invasion in colorectal lesions. RESULTS: The mean age of patients was 63 years, with a higher proportion of males (60.9%). Lesions measuring 10-20 mm were predominant (83.7%). The majority were located in the left colon. Flat lesions were the most common endoscopic appearance (57.8%). The final pathology results showed precancerous lesions, intramucosal cancers, superficial submucosal invasion carcinoma and deep submucosal invasion carcinoma were 40.1%, 38.4%, 8.3% and 13.2% respectively. ESD was directly performed in 95.2% of cases (275 lesions). Surface fullness (OR = 13.81), dilated blood vessels in tumor periphery (OR = 6.44), JNET2B (OR = 6.43), JNET3 (OR = 22.94), and de novo carcinoma pathway (OR = 21.61) were independent risk factors for deep submucosal invasion in early colorectal cancer. Chicken skin mucosa (CSM) (OR = 5.71), surface depression (OR = 12.38), and invasive pit pattern (OR = 161.18) were independent risk factors for malignancy in non-pedunculated colorectal polyps less than 2 cm. The preliminary nomogram constructed based on these independent risk factors demonstrated predictive value for deep submucosal invasion in early-stage colorectal cancer. CONCLUSIONS: Non-pedunculated colorectal lesions smaller than 2 cm carry risks of malignancy and deep submucosal invasion. Surface fullness, dilated blood vessels in tumor periphery, type JNET2B/3, and de novo carcinoma pathway are independent risk factors for deep submucosal invasion. CSM, surface depression, and invasive pit pattern are independent risk factors for malignancy. The nomogram prediction model constructed based on these findings provides a basis for clinical decision-making. The preliminary nomogram developed from these findings could offer some guidance for clinical decision-making.