Number and size of lymph nodes and node metastases in rectal carcinomas

Assessment of lymphatic spread is an important factor in staging rectal cancer. Knowledge of the presumed number and size of metastases present is essential before assessment of the accuracy of preoperative visualization of node metastases can be undertaken. We examined the lymph nodes of 196 patients with rectal carcinoma. Among 4985 lymph nodes, 586 metastases were found. Ninety-eight patients had metastases in pararectal nodes and in nodes along the superior rectal artery. These nodes are potentially visible by ultrasound. In 31 of these patients (32%), all metastases were 5 mm or less and in 8 cases (8%) 2 mm or less. These small nodes are difficult to see on ultrasound. We also found significant relationships between depth of invasion, grade of differentiation and lymphatic spread. These data suggest that a careful histological search for small metastases should be undertaken to avoid false-negative lymph node findings.