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The relationship between age of the patient and the histologic gradation of mucosal polyps (total 331 cases) and invasive carcinoma of the large intestine was studied in a surgical series (261 cases) as well as in an autopsy series (3,178 cases). The average ages of the patients increased steadily with the advance of histologic atypism from 40.7 years with grade I polyps to 58.7 years with invasive carcinoma in the autopsy series. From the differences in average ages of the patients, a provisional estimation of the periods which might be required for polyps of each grade to become malignant and to kill patients was attempted. The following figures were suggested; 3.6 years for polyps of grade V pseudostratification, 8.3 years for grade IV, 11.4 years for grade III, 13.1 years for grade II, and 18.0 years for grade I.
Kozuka et al. (Mon,) studied this question.