Mesorectal microfoci adversely affect the prognosis of patients with rectal cancer

Mesorectal involvement is a common feature in rectal tumors. Neoplastic foci can be identified at pathologic examination of the mesorectum, but their incidence and prognostic significance remain to be defined.

A series of 77 patients with extraperitoneal rectal cancer, resected with total mesorectal excision, entered the study. After fixation, the excised specimens were submitted to serial transverse sections and staining. Direct tumor infiltration, lymph node involvement, and neoplastic microfoci in the mesorectum were investigated. Patients with mesorectal foci were compared with those without deposits with regard to clinical and pathologic parameters; different patterns of foci (endovasal, endolymphatic, perineural, isolated) were also considered. Univariate and multivariate analyses were used to evaluate the impact on survival rate.

Neoplastic mesorectal involvement was found in 64 patients (83.1 percent). Direct tumor infiltration was detected in 66.2 percent, node involvement in 28.6 percent, microscopic foci in 44.2 percent of cases (endovasal in 11.7 percent, endolymphatic in 15.7 percent, perineural in 26 percent, isolated in 14.3 percent). In 7 cases (10.9 percent) microfoci alone (without any kind of other mesorectal involvement) were detected. Deposits were found in 18.8 percent of TNM Stage I tumors, in 46.9 percent of Stage II and in 59.3 percent of Stage III cancers. Similar incidence was found in patients treated with integrated therapies and surgery alone (43.3 vs. 44.7 percent, P = not significant). Poorer median (44.5 vs. 57 months, P = 0.04) five-year overall survival rate (43.4 vs. 63.3 percent, P = 0.016) and disease-free survival rate (43.3 vs. 57.7 percent, P = 0.048) were observed in patients with microscopic foci compared with those without deposits. Tumor configuration was found to be a independent prognostic factor for both overall and disease-free survival rates; furthermore, endolymphatic, perineural, and isolated foci significantly affected overall survival rate, while TNM staging affected disease-free survival rate.

The incidence of neoplastic foci in the mesorectum is high, even in early staged tumors and despite aggressive preoperative treatment. They seem to affect prognosis. Such features should, therefore, be considered when local excision of the tumor is planned. Presence of mesorectal foci should modify conventional staging of the rectal tumor.