Ploidy analysis prediction of transformation in potentially malignant oral diseases
Aims: To investigate the predictive ability of image-based ploidy analysis in a UK patient population including potentially malignant oral diseases as well as low risk cases.
Methods: Formalin-fixed paraffin embedded tissue blocks from 1171 biopsy specimens taken from 621 patients with potentially malignant diseases were selected as consecutive eligible cases accessioned between 1990 to 1999. Nuclei were extracted from sections 50 microns thick by enzyme digestion, cytospin monolayers prepared and stained with Feulgen stain and subjected to image-based ploidy analysis. DNA content was determined in a minimum of 300 cells on a Fairfield ploidy analyser, compared to internal controls and the histograms classified into diploid, tetraploid and aneuploid on the basis of previously published criteria (Sudbo et al. N Engl J Med, 2001. 344:1270). Malignant transformation was determined from pathology department, hospital records, Thames Cancer Registry and the Office of National Statistics.
Results: Lesions from 63 patients (10.1%) progressed to oral OSCC, of which all lesions were diploid in 13 cases (20.6%), at least one was non-diploid in 33 cases (52.4%). Lesions from 17 (27%) yielded inconclusive ploidy results for a variety of reasons including small specimen size. Of the 558 (89.9%), patients that did not develop carcinoma, all lesions in 211 (37.8%) were diploid, at least one was non-diploid in 122 (21.8%) and in 225 (40.4%) were inconclusive.
Conclusions: Ploidy analysis predicted malignant transformation in the majority of patients but this lower risk lesion population includes more apparently innocuous aneuploid lesions that previously published series. If applied to routine pathology service without changing procedures, many specimens would be too small for analysis.