title: Tumour growth is more dispersed in pancreatic head cancers than in rectal cancer: implications for resection margin assessment.
abstract: OBJECTIVE
  The UK definition of microscopic resection margin involvement (R1) in pancreatic head cancer, based on tumour lying <1 mm from the margin, has been adopted from rectal cancer, but has never been validated. The aim of this study was to assess the adequacy of the R1 definition for pancreatic head cancers by comparing the growth patterns of rectal (RC), pancreatic (PC), ampullary (AC) and distal bile duct (DBC) adenocarcinomas.
  
  
  RESULTS
  Distances between tumour cells and tumour cell density in the tumour centre and periphery were quantified by Minimum Spanning Tree (MST) analysis in 10 cases of the four cancer groups. In RC, the MST distance was similar throughout the entire width of the tumour, whereas in PC, DBC and AC it was significantly larger at the periphery than at the tumour centre (P ≤ 0.003). While results were similar for PC and DBC, however, distances at the centre and periphery of both cancers were larger compared to AC (P ≤ 0.046). Tumour cell density dropped at the periphery of PC to 31% of that at the centre, compared to 83% in RC (P < 0.0002).
  
  
  CONCLUSIONS
  Tumour growth in pancreatic head cancers is more dispersed than in RC, particularly in the tumour periphery. Revision of the R1 definition for pancreatic head cancer may therefore need to be considered.
authors.affiliation: Department of Histopathology, St James's University Hospital, The Leeds Teaching Hospitals NHS Trust, Leeds, UK. cverbeke@doctors.org.uk
authors.forename: Caroline Sophie
authors.initials: CS
authors.lastname: Verbeke
authors.forename: Johannes
authors.initials: J
authors.lastname: Knapp
authors.forename: Ivar Prydz
authors.initials: IP
authors.lastname: Gladhaug
mesh_terms: D000230:Adenocarcinoma / Q000473:pathology* / Q000601:surgery; D021441:Carcinoma, Pancreatic Ductal / Q000473:pathology* / Q000601:surgery; D013505:Digestive System Surgical Procedures / Q000592:standards*; D018450:Disease Progression; D006801:Humans; D010190:Pancreatic Neoplasms / Q000473:pathology* / Q000601:surgery; D012004:Rectal Neoplasms / Q000473:pathology* / Q000601:surgery