The number of lymph nodes is correlated with mesorectal morphometry

Abstract

Lymph node involvement is one of the most significant prognostic factors of patients with rectal cancer. However, the distribution of mesorectal lymph nodes is not well known. This study was designed to assess lymph nodes in the mesorectum and to evaluate the correlation between the volume and weight of the mesorectum and the number of lymph nodes. The mesorectums of 20 human cadavers were studied. The volume and weight of the superior rectal mesentery, superior mesorectum and inferior mesorectum were measured. Lymph nodes were sought by manual dissection and were submitted for histological examination. The correlation between the number of lymph nodes and the volume and weight of the mesorectum was evaluated by non-parametric Spearman test. A total of 178 lymph nodes were identified. The mean number of lymph nodes per specimen was 9.2 +/- 4.5. The lymph nodes were mostly smaller than 3 mm and located in the superior and posterior parts of the mesorectum. A positive correlation was found between the number of mesorectal lymph nodes and the volume and weight of the mesorectum. The number of lymph nodes in the superior rectal mesentery was independent of its volume and its weight. Mesorectal lymph nodes are mainly located above the peritoneal reflection within the posterior mesorectum. The positive correlation between the volume or the weight of the mesorectum and the number of mesorectal lymph nodes should be considered as a possible means to determine the minimum number of mesorectal lymph nodes required for histological examination.