ATYPICAL MITOSES IN LESIONS OF THE ORAL-MUCOSA - A NEW INTERPRETATIONOF THEIR IMPACT UPON TUMORIGENESIS

With regard to the classification of precancerous lesions, this is the first approach to compare modes of the cell cycle in benign lesions a nd neoplasia in oral mucosa. The main objective of this study was to f ind parameters that indicate possible progress in tumorigenesis. In th is respect, histomorphological changes were compared with the DNA cont ent of individually identified nuclei in interphase and division. Thus , hyperplastic tissue was discriminated from neoplastic tissue by inve stigating pyogenic granulomas (27 cases), epulides (17), simple forms of ulcers (12), low-grade dysplasias (14), high-grade dysplasias (15) and carcinomas (41). After diagnosis, Feulgen DNA was quantified from interphase nuclei and chromosome division figures (CDFs) in 8- and 15- mu m sections. Interphase nuclei hom cases of hyperplasia were constan tly found in the range of mitotic amounts, i.e. 2 c-4 c DNA. A 4 c val ue was therefore recorded for mitotic figures. Measurements in this ty pe of lesion were carried out with a high degree of accuracy (CV at 0. 05). However, cases of neoplasia showed CDFs that were frequently beyo nd the mitotic range (>4.8 c) in morphologically identified prophases, metaphases and both hemispheres of telophases. The distribution profi le of interphase nuclei was characterised by DNA aneuploidy, with a 5 c exceeding rate (ER) > 5%. This biological variability in the amount of nuclear DNA was reflected by CV>0.20. The quantitative results corr oborated the morphological two-level classification of premalignant le sions caused by endoreplication associated with neoplasia. Thus, regul ar mitotic replication appeared to be progressively substituted by gen ome multiplication. (C) 1997 Elsevier Science Ltd.