title: In vivo lymph node mapping and pattern of metastasis spread in locally advanced mid/low rectal cancer after neoadjuvant chemoradiotherapy.
abstract: OBJECTIVE
  The lymph node status is one of the strongest prognostic determinants in rectal cancers. After chemoradiotherapy (CRT), lymph nodes are difficult to detect. This study aims to evaluate the feasibility of lymph node mapping in the mesorectum after CRT to analyze the pattern of metastasis spread and to assess the reliability of blue dye injection in sentinel lymph node detection.
  
  
  METHODS
  Ten patients with cN+ mid/low RCs after CRT were prospectively enrolled. The protocol scheduled intraoperative blue dye injection, surgery, and specimen examination with fat clearance technique. The mesorectum was divided into three equal "levels" (upper, middle, and lower); each level was divided into three equal "sectors" (right anterolateral, posterior, and left anterolateral). Lymph nodes were defined "small" if ≤5 mm.
  
  
  RESULTS
  Two hundred seventy-six lymph nodes were retrieved in ten patients; 76.5 % were small lymph nodes. Six patients were pN+ (33 metastatic lymph nodes, 76 % small); small lymph node analysis upstaged one patient from N0 to N1 and four patients from N1 to N2. Metastasis distribution across sectors was continuous, without "skip sectors." The blue dye detected the sentinel lymph node in all patients; in half of the cases, it was out of the tumor sector. Blue dye identified 69.7 % of metastatic lymph nodes; its sensitivity decreased together with the metastatic deposit size (84 % macrometastases, 28.6 % micrometastases, 0 % occult tumor cells; p = 0.004).
  
  
  CONCLUSIONS
  The fat clearance technique should be the standard pathological examination in patients with RCs after CRT; N staging was improved by small lymph node identification. Lymph node metastases have a continuous spread through mesorectal sectors. Blue dye injection is effective in sentinel lymph node detection.
authors.affiliation: Department of HPB and Digestive Surgery, Ospedale Mauriziano Umberto I, Largo Turati 62, 10129, Turin, Italy.
authors.forename: E
authors.initials: E
authors.lastname: Farinella
authors.forename: L
authors.initials: L
authors.lastname: Viganò
authors.forename: M C
authors.initials: MC
authors.lastname: Fava
authors.forename: M
authors.initials: M
authors.lastname: Mineccia
authors.forename: F
authors.initials: F
authors.lastname: Bertolino
authors.forename: L
authors.initials: L
authors.lastname: Capussotti
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D059248:Chemoradiotherapy; D006801:Humans; D007430:Intraoperative Care; D008198:Lymph Nodes / Q000473:pathology*; D008207:Lymphatic Metastasis / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D020360:Neoadjuvant Therapy; D009367:Neoplasm Staging; D012004:Rectal Neoplasms / Q000188:drug therapy / Q000473:pathology* / Q000532:radiotherapy / Q000628:therapy*