Pathological assessment of pericolonic tumor deposits in advanced colonic carcinoma: relevance to prognosis and tumor staging

The current TNM classification considers a tumor nodule in the pericolic/perirectal adipose tissue as venous invasion if the nodule has an irregular contour and as regional lymph node metastasis if the nodule has the form and smooth contour of a lymph node. However, detailed studies on the clinico-pathological implications of pericolonic tumor deposits and of extranodal extension are still lacking. We investigated the impact of these metastatic deposits in the pericolic fat in a series of 228 patients with advanced colon cancer. The pericolonic tumor deposits were characterized by their appearance, size, distance from the primary tumor and by their relation with the lymphatic tissue not organized in lymph nodes. These features were then compared with the clinico-pathological characteristics of the tumors and with the patients' survival. All these lesions were associated with reduced disease-free and overall survivals in a univariate analysis, but only pericolonic tumor deposits retained an independent prognostic role in the multivariate analysis. Our findings suggest that pericolonic tumor deposits are a destructive type of venous invasion different from other types of vessel involvement, and that these lesions may rather be included in the M category for staging purposes.