Metastatic potential of colorectal adenoma containing carcinoma determined by pre-operative assessment of morphology.

BACKGROUND/AIMS: Colectomy with lymphadenectomy is sometimes considered to be the appropriate management for patients with colorectal carcinoma in adenoma invading beyond the muscularis mucosa. Our study was done to determine whether gross features of the tumor would provide information to predict the metastatic potential.

MATERIAL AND METHODS

Thirty one carcinomas in adenomas from 29 patients were surgically resected. Macroscopic findings with regard to size and morphologic type were compared with the presence or absence of lymph node metastasis and vessel invasion.

RESULTS

The rate of lymph node metastasis in all cases was 20.0% (6/30). Lymphatic and venous invasion was also identified in 7 (22.6%) and 5 (16.1%) cases, respectively. There was no evidence of nodal involvement in pedunculated lesions, but the incidence of nodal involvement was 18.8% and 60.0% in sessile and protruded tumors, respectively. There was a significant correlation between morphologic type and the incidence of lymph node metastasis. The mean size of node positive tumors was 5.9 cm with a range of 3.8-9.0 cm, that is significantly larger than the value of 3.8 cm in cases of node negative tumors. All the node positive tumors exceeded 3.5 cm. With adjustment made for the morphology, the estimated risk of nodal involvement of tumors with a sessile shape and larger than 3.5 cm was 33.3%. Therefore, both large sessile and protruded types mean a high risk for lymph node metastasis.

CONCLUSIONS

Macroscopic features, size and gross type are critical factors in determining the metastatic potential of carcinoma in colorectal adenoma. We recommend segmental colectomy with lymphadenectomy for such patients.