title: Perineural invasion in pT3N0 rectal cancer: the incidence and its prognostic effect.
abstract: BACKGROUND
  The authors' purpose was to explore the incidence and prognostic significance of perineural invasion (PNI) in pT3N0 rectal cancer.
  
  
  METHODS
  Pathologic materials from resected specimens of 173 patients with pT3N0 rectal cancer were retrospectively collected. PNI-positivity was categorized into 2 groups: surrounding the nerve sheath (SS-PNI) and invading through the nerve sheath (TS-PNI). The rate of PNI-positivity was compared with PNI as initially recorded in the original reports. Patients' outcome was studied in groups with different PNI status, and multivariate analysis was performed to determine its prognostic value.
  
  
  RESULTS
  In this retrospective analysis, PNI-positivity was found in 24.3% of all cases, in which SS-PNI and TS-PNI were 11% and 13.3%, respectively, and was related to lymphovascular invasion. Only 7.5% of patients' specimens were reported as PNI-positive in the original reports. Detection of SS-PNI was likelier to be missed than TS-PNI. The rates of local recurrence, disease-free survival, and overall survival at 5 years were similar between the groups of SS-PNI and TS-PNI. The 5-year local recurrence rate was more than 2.5-fold higher in the PNI-positive group compared with the PNI-negative group (22.7% vs 7.9%, respectively; P = .017). Multivariate analysis proved that PNI-positivity was the only independent risk factor for predicting 5-year local recurrence rate, whereas only sampled lymph nodes was related to 5-year disease-free survival and overall survival.
  
  
  CONCLUSIONS
  PNI is a common pathologic feature in rectal cancer. The definition of PNI should include SS-PNI and TS-PNI. Rectal cancer patients who are PNI-positive are at higher risk of local recurrence and should be considered for more intensive treatment.
authors.affiliation: Department of Colorectal Surgery, Cancer Hospital of Fudan University, Department of Oncology, Shanghai Medical College, Fudan University, Shanghai, People's Republic of China.
authors.forename: Junjie
authors.initials: J
authors.lastname: Peng
authors.forename: Weiqi
authors.initials: W
authors.lastname: Sheng
authors.forename: Dan
authors.initials: D
authors.lastname: Huang
authors.forename: Alan P
authors.initials: AP
authors.lastname: Venook
authors.forename: Ye
authors.initials: Y
authors.lastname: Xu
authors.forename: Zuqing
authors.initials: Z
authors.lastname: Guan
authors.forename: Sanjun
authors.initials: S
authors.lastname: Cai
mesh_terms: D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D009361:Neoplasm Invasiveness; D009364:Neoplasm Recurrence, Local; D010524:Peripheral Nervous System Neoplasms / Q000556:secondary*; D011379:Prognosis; D012004:Rectal Neoplasms / Q000401:mortality / Q000473:pathology*