title: Inguinal lymph node metastases are recognized with high frequency in rectal adenocarcinoma invading the dentate line. The histological features at the invasive front may predict inguinal lymph node metastasis.
abstract: OBJECTIVE
  Inguinal lymph node (ILN) metastasis occurs with high frequency in some of the patients with lower rectal cancer. The aim of this study was to identify risk factors for ILN metastasis in patients with low rectal adenocarcinoma.
  
  
  METHODS
  We retrospectively analysed 156 patients with lower rectal adenocarcinoma who underwent radical resection (R0) at a single institution.
  
  
  RESULTS
  Twenty-five (16%) patients had a tumour that invaded the dentate line, seven of whom had ILN metastasis. Invasion of the dentate line was significantly associated with a high rate of ILN metastasis, worse prognosis and local recurrence than with a tumour not invading the dentate line (P = 0.03). A Cox proportional hazard regression analysis revealed the histological characteristics at the invading front (Hif) also to be a risk factor for ILN metastasis.
  
  
  CONCLUSIONS
  Tumours which invade the dentate line have a high rate of ILN metastases and worse cancer specific end-points. The presence of poorly differentiated or mucinous adenocarcinoma components is an indication for bilateral groin irradiation.
authors.affiliation: Department of Colorectal Surgery, Seirei Hamamatsu General Hospital, Hamamatsu, Shizuoka, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Hamano
authors.forename: Y
authors.initials: Y
authors.lastname: Homma
authors.forename: Y
authors.initials: Y
authors.lastname: Otsuki
authors.forename: S
authors.initials: S
authors.lastname: Shimizu
authors.forename: H
authors.initials: H
authors.lastname: Kobayashi
authors.forename: Y
authors.initials: Y
authors.lastname: Kobayashi
mesh_terms: D000230:Adenocarcinoma / Q000473:pathology / Q000556:secondary* / Q000601:surgery; D000368:Aged; D005260:Female; D006801:Humans; D007264:Inguinal Canal; D008198:Lymph Nodes / Q000473:pathology*; D008207:Lymphatic Metastasis; D008297:Male; D008875:Middle Aged; D009361:Neoplasm Invasiveness; D009364:Neoplasm Recurrence, Local; D016016:Proportional Hazards Models; D012004:Rectal Neoplasms / Q000473:pathology* / Q000601:surgery; D012189:Retrospective Studies; D012307:Risk Factors