[Distribution of micrometastatic nodules of low rectal cancer in mesorectum: a pathological study using whole-mount sections].
OBJECTIVE
To investigate the regional spread of micrometastatic nodules in the mesorectum from low rectal cancer, and provide further pathological evidence to optimize radical resection procedure for rectal cancer.


METHODS
A total of 62 patients with low rectal cancer underwent low anterior resection and total mesorectal excision (TME) was included in this study. Surgical specimens were sliced transversely and serial embedded blocks were made at 2.5 mm interval, and paraffin sections were stained with hematoxylin and eosin. The mesorectum on whole-mount sections was divided into three regions: outer region of mesorectum (ORM), middle region of mesorectum (MRM) and inner region of mesorectum (IRM). Microscopic spread were examined microscopically on the sections for the distribution in different mesorectal regions, frequency, types, involvement of lymphatic system and correlation with the primary tumor.


RESULTS
Microscopic spread of the tumor in mesorectum and ORM was observed in 38.7% (24/62) and 25.8% (16/62) of the patients, respectively. Circumferential resection margin (CRM) involved by microscopic tumor foci occurred in 6.5% (4/62) of the patients, and distal mesorectum (DMR) involvement was recorded in 6.5% (4/62) with a spread extent within 3 cm of distal border of the main lesions. Most (20/24) of the patients with microscopic spread in mesorectum were in TNM stage III.


CONCLUSIONS
Results of the present study support that complete excision of mesorectum without destruction of the ORM is essential for surgical management of low rectal cancer, and an optimal DMR clearance resection margin should not be less than 4 cm.
Wang
Zhao
Z
Department of Gastroenterological Surgery, Institute of Digestive Surgery, West China Hospital, Sichuan University, Chengdu 610041, China.
Zhou
Zong-guang
ZG
Wang
Cun
C
Han
Fang-hai
FH
Chen
You-dai
YD
Yan
Wen-wei
WW
Gao
Hong-kai
HK
Wang
Yong
Y
Li
Hong-guang
HG
D000230:Adenocarcinoma / Q000473:pathology* / Q000601:surgery; D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D008198:Lymph Nodes / Q000473:pathology; D008207:Lymphatic Metastasis; D008297:Male; D008643:Mesentery / Q000473:pathology / Q000601:surgery; D008875:Middle Aged; D009361:Neoplasm Invasiveness; D009367:Neoplasm Staging; D018365:Neoplasm, Residual; D009360:Neoplastic Cells, Circulating / Q000473:pathology; D010534:Peritoneal Neoplasms / Q000473:pathology / Q000601:surgery; D012004:Rectal Neoplasms / Q000473:pathology* / Q000601:surgery; D012007:Rectum / Q000601:surgery*