Atypical mitoses in elevated dysplasias of the stomach.

The number and topographic localization of spontaneously occurring mitotic figures were studied in 22 elevated dysplasias of the stomach. The lesions were divided into 3 equally thick zones. Mitoses occurred in 5 of 7 slight dysplasias, in 7 of 8 moderate dysplasias, and in all 7 severe dysplasias. When present, mitoses were localized to the superficial zone in slight, moderate and severe dysplasias, in the middle zone in some moderate dysplasias, and in almost all severe dysplasias. In the deeper zone, mitoses were seen in one of the moderate dysplasias and in as much as 5 of the severe dysplasias. The number of mitoses were significantly higher in moderate and severe dysplasia, when compared to slight dysplasia. The percentage of atypical mitoses increased gradually from 27% in slight dysplasia to 41% in moderate, and 52% in severe dysplasias. In the adjacent, non-dysplastic gastric mucosa, a 1.5% of atypical mitoses was found. Significantly higher amounts of atypical mitoses were recorded in severe dysplasias, as compared to slight and moderate dysplasias. The results suggest that the various types of elevated dysplasias (slight, moderate and severe) of the stomach may be distinguished, not only by the characteristics of the atypical cells in interphase--as is the case today--but also by the topographic distribution of mitoses and by the difference in percentage of atypical mitoses occurring in these lesions. The possible significance of the mitosis as a biohistological marker of the behaviour of elevated dysplasias of the stomach is discussed.