The histological characteristics of clinically normal mucosa adjacent to oral cancer.

Background: The 'field cancerization' theory tries to explain the risk of local recurrences and development of second primary tumors in oral sqamous cell carcinoma (OSCC) patients. According to this theory it is assumed that clinically normal mucosa adjacent to oral cancer, except molecular, has already developed certain premalignant histopathological changes.

Aims: The aim of this study was to determine histological characteristics of clinically normal-looking mucosa at different distances from the apparent tumor lesion margins in OSCC patients.

Materials And Methods: Normal-appearing oral mucosa biopsy specimens were obtained from 30 new (untreated) oral cancer patients from sites at a distance of 10 mm and 20 mm from the tumor lesion margins and were compared with normal oral mucosa from 30 control patients with benign oral lesions.

Results: A total of 21 patients (70%) in the OSCC group demonstrated histological abnormalities under microscopic examination versus 7 (23.3%) control patients (P<0.01). Seventeen oral cancer patients (57%) showed significant difference in incidence and type of histological changes of normal-looking mucosa at a distance of 10 mm from the tumor lesion; 8 (27%) demonstrated reactive changes, 6 (20%) mild dysplasia and 3 (10%) squamous cell carcinoma, compared to histological abnormalities registered in 11 (OSCC) patients (36%) at a distance of 20 mm from the tumor; 10 (33%) displayed reactive changes and 1 (3%) mild dysplasia.

Conclusions: Histological abnormalities of clinically normal-looking oral mucosa taken at different distances from the tumor lesion indicated the existence of subclinical field change and represent an important parameter during the assessment of the adequacy of surgical resection margins in oral cancer management.