Small carcinomas involving less than one-quarter of the rectal circumference: local excision is still associated with a high risk of nodal positivity.

Aim: A study was carried out to determine the relationship between mesorectal lymph nodal involvement and T stage in a group of patients with a rectal cancer involving less than one-quarter of the rectal circumference, such as might be selected for local excision.

Method: The data of patients having rectal resection between 2010 and 2014 were prospectively entered in a rectal carcinoma registry. A model for describing tumours involving less than one quadrant of the rectal circumference was created to facilitate the evaluation process.

Results: In all, 304 patients were included in the study. In 68 (22.4%) a small tumour (< 1 quadrant involved) was found. Of these, 26.5% had positive mesorectal lymph nodes (N+). In lesions of Stage ypT0 cancer 12.5% patients were node positive, in Stage Tis and T1 tumours there was no case of node positivity, but in Stage T2 and Stage T3 cancers the incidence of node positivity was 27.5% and 64%.

Conclusion: The study demonstrated that, even for small tumours involving only one rectal quadrant, the risk of lymph nodal involvement was about 25%. Had the patients undergone local excision the treatment would have been incomplete.