[Precancerous stages of the oral mucosa--possible identification of obligatory precancerous conditions].

Macroscopically and microscopically precancerous lesions of the oral mucosa cannot be diagnosed with sufficient accuracy. Dysplasias represent a particular diagnostic difficulty. The reproducibility of grading of dysplasias may be increased by the quantification of morphological parameters using image analysis systems. However an unequivocal identification of obligatory precancerous lesions cannot be attained by this method. Measurement of the nuclear DNA content represents a non-morphological method for the identification of obligatory precancerous lesions. The diagnostic criterion of malignancy is aneuploidy. Structural or numerical chromosomal aberrations that are absent in benign tumours and normal cells typify aneuploidy. Aneuploidy is manifested by an atypical nuclear DNA distribution that can be identified objectively by suitable algorithms. Dysplasias of the squamous epithelium with aneuploid nuclear DNA contents are regarded as obligatory precancerous lesions. DNA measurements, computation of data and printout of a 'DNA diagnosis' are possible with a TV-image analysis system and an automated microscope within 30 min.