Morphological characteristics of lateral pelvic lymph nodes in locally advanced lower rectal cancer: A retrospective study

AIM: This study aimed to investigate the potential of the size and aspect ratio of metastatic and non‐metastatic lateral pelvic lymph nodes (LPLNs) as low‐risk markers for locally advanced lower rectal cancer, without treatment by neoadjuvant chemoradiation therapy or LPLN dissection. METHODS: This single‐center, retrospective cohort study evaluated 310 consecutive patients diagnosed with lower rectal cancer (T: T3/T4, N: any, and M: M0) who underwent curative surgery without neoadjuvant therapies between 2010 and 2018. The harvested LPLNs were categorized into groups A (metastasis‐positive lymph nodes), B (metastasis‐negative lymph nodes in the area bearing metastasis‐positive lymph nodes), C (metastasis‐negative lymph nodes in a metastasis‐negative area in metastasis‐positive patients), and D (lymph nodes in non‐metastatic patients). The main outcome measure was the relationship among lymph node size, aspect ratio, and metastasis in the LPLNs. RESULTS: Overall, 3962 LPLNs were harvested. The long and short axes and the aspect ratio were significantly longer and higher, respectively, in group A than in the other groups (P < .001). The aspect ratio in group B was significantly higher than that in groups C and D (P < .001). The aspect ratio in group C was significantly higher than that in group D (P < .001). Furthermore, no metastasis‐positive lymph nodes had an aspect ratio of less than 0.4. Metastasis‐positive LPLNs tended to be larger and rounder than their metastasis‐negative counterparts. CONCLUSIONS: Metastatic LPLNs in patients with lower rectal cancer are significantly larger and have a higher aspect ratio. Lymph nodes with aspect ratios of <0.4 were metastasis negative.