COLORECTAL ADENOCARCINOMA - QUALITY OF THE ASSESSMENT OF LYMPH-NODE METASTASES

PURPOSE: We have studied 193 cases of colorectal adenocarcinoma from a population-based register to determine the minimum number of lymph no des to be examined to provide an accurate assessment of the presence o f nodal metastases. METHODS: The mean total number of lymph nodes iden tified per surgical specimen was 11 +/- 6.8 (range, 1-36) using tradit ional dissection. One hundred eighteen specimens (61 percent) were cla ssified as Dukes B. Seventy-five (39 percent) had lymph node metastase s (Dukes C) with a mean of 3.3 +/- 4.7 positive lymph nodes per specim en. With binomial distribution we calculate the probability to find at least one positive node in a sample size n with a determined proporti on of positive nodes. RESULTS: The error probability in the ganglionar assessment by traditional dissection was 0.05 with 6 examined lymph n odes and 0.01 with 10 examined nodes. CONCLUSION: We must provide the pathologist with a minimum of six examined lymph nodes per surgical sp ecimen for an optimal Dukes B assessment.