title: Malignant transformation in 1458 patients with potentially malignant oral mucosal disorders: a follow-up study based in a Taiwanese hospital.
abstract: BACKGROUND
  It is generally accepted that the development of cancer in the oral mucosa is preceded by an identifiable non-invasive precursor lesion. The aim of this follow-up study was to estimate the rate and the time to transformation in a group of patients from southern Taiwan with potentially malignant oral epithelial lesions.
  
  
  METHODS
  The follow-up time is defined as the duration between the onset of the initial diagnosis and the occurrence of confirmed oral cancer. A total of 1458 patients with histological diagnoses of various pre-malignant oral lesions were followed up between 1991 and 2001. The average age at initial diagnosis was 47.5 years. The histological diagnoses were divided into six categories: epithelial dysplasia with hyperkeratosis/epithelial hyperplasia (8.85%); epithelial dysplasia with submucous fibrosis (2.54%); submucous fibrosis (27.57%); hyperkeratosis/epithelial hyperplasia (29.01%); lichen planus (9.80%) and verrucous hyperplasia (22.22%).
  
  
  RESULTS
  Within the cohort of 1458 patients, 44 patients progressed to oral cancer in the same site as the initial lesions with an overall transformation rate of 3.02% and a mean follow-up time of 42.64 months. Eight of the 166 patients with dysplastic lesions and 15 of 423 patients with hyperkeratosis/epithelial hyperplasia progressed to malignancy. The other patients with malignant transformation originated from various pre-cancerous oral lesions and conditions (submucous fibrosis, eight of 402; lichen planus, three of 143; verrucous hyperplasia, 10 of 324).
  
  
  CONCLUSIONS
  These results indicate that patients with pre-malignant oral lesions need long-term follow up.
authors.affiliation: Department of Oral Pathology, School of Dentistry, College of Dental Medicine, Kaohsiung Medical University, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan.
authors.forename: Shue-Sang
authors.initials: SS
authors.lastname: Hsue
authors.forename: Wen-Chen
authors.initials: WC
authors.lastname: Wang
authors.forename: Chung-Ho
authors.initials: CH
authors.lastname: Chen
authors.forename: Cheng-Chung
authors.initials: CC
authors.lastname: Lin
authors.forename: Yuk-Kwan
authors.initials: YK
authors.lastname: Chen
authors.forename: Li-Min
authors.initials: LM
authors.lastname: Lin
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D002471:Cell Transformation, Neoplastic / Q000473:pathology*; D015331:Cohort Studies; D018450:Disease Progression; D004848:Epithelium / Q000473:pathology; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D006965:Hyperplasia; D007972:Leukoplakia, Oral / Q000473:pathology; D017676:Lichen Planus, Oral / Q000473:pathology; D008297:Male; D008875:Middle Aged; D009059:Mouth Diseases / Q000473:pathology; D009062:Mouth Neoplasms / Q000473:pathology*; D009914:Oral Submucous Fibrosis / Q000473:pathology; D011230:Precancerous Conditions / Q000473:pathology*; D013624:Taiwan; D013997:Time Factors; D014860:Warts / Q000473:pathology