title: Recurrence rate and shift in histopathological differentiation of oral squamous cell carcinoma – A long-term retrospective study over a period of 13.5 years.
abstract: OBJECTIVE
  Little information is available as to whether recurrences of oral squamous cell carcinoma (OSCC) show different histopathological grades than the primary tumor and whether postoperative radiotherapy (PORT) influences the grade of differentiation in the case of recurrence. The objective of this study was the evaluation of recurrence rates and change in differentiation.
  
  
  METHODS
  This retrospective, single-institution cohort study included surgically treated OSCC patients over a 13-year period (2000-2013). The relationship among tumor size, lymph node metastases, and recurrence rate of OSCC was investigated. Primary tumor differentiation was compared with differentiation of recurrence.
  
  
  RESULTS
  A total of 429 patients (277 men and 152 women) were included in this study. Of these, 124 (28.9%) received PORT. The incidence of primary cervical metastases increased significantly with tumor size (p < 0.001). Recurrence developed in 82 patients (19.1%). Stage T1/T2 showed a significantly lower recurrence rate than stage T3/T4 (16.3% vs. 30.2%) (p < 0.01). A total of 23 (30.7%) patients with recurrence showed a change in differentiation.
  
  
  CONCLUSIONS
  Increasing primary tumor size correlates with incidence of cervical metastases and recurrence rate. Initial cervical metastases show no effect on recurrence rates. Differentiation of primary tumor does not correlate with the recurrence rate. The majority of recurrences show consistent histopathological grading.
authors.affiliation: Department of Oral and Maxillofacial Surgery, University Medical Center Freiburg, Hugstetter Straße 55, D-79106 Freiburg, Germany. Electronic address: michael.ermer@uniklinik-freiburg.de.
authors.forename: M A
authors.initials: MA
authors.lastname: Ermer
authors.affiliation: Department of Oral and Maxillofacial Surgery, University Medical Center Freiburg, Hugstetter Straße 55, D-79106 Freiburg, Germany.
authors.forename: K
authors.initials: K
authors.lastname: Kirsch
authors.affiliation: Department of Oral and Maxillofacial Surgery, University Medical Center Freiburg, Hugstetter Straße 55, D-79106 Freiburg, Germany.
authors.forename: G
authors.initials: G
authors.lastname: Bittermann
authors.affiliation: Department of Oral and Maxillofacial Surgery, University Medical Center Freiburg, Hugstetter Straße 55, D-79106 Freiburg, Germany.
authors.forename: T
authors.initials: T
authors.lastname: Fretwurst
authors.affiliation: Center for Medical Biometry and Medical Informatics, Institute for Medical Biometry and Statistics, University Medical Center Freiburg, Stefan-Meier-Str. 26, D-79104 Freiburg, Germany.
authors.forename: K
authors.initials: K
authors.lastname: Vach
authors.affiliation: Department of Oral and Maxillofacial Surgery, University Medical Center Freiburg, Hugstetter Straße 55, D-79106 Freiburg, Germany.
authors.forename: M C
authors.initials: MC
authors.lastname: Metzger
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002294:Carcinoma, Squamous Cell / Q000473:pathology*; D002454:Cell Differentiation; D015331:Cohort Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009062:Mouth Neoplasms / Q000473:pathology*; D060787:Neoplasm Grading; D009364:Neoplasm Recurrence, Local; D012189:Retrospective Studies; D055815:Young Adult
keywords: Cervical lymph node metastases; Differentiation; Grading; Oral squamous cell carcinoma (OSCC); Recurrence rate