“…The exact incidence of malignant change varies, usually ranging from 1o% to 14% (Edwards and Truelove, 1964), whereas in the population at large the incidence is 0.06 % (Weckesser and Chinn, 1953). It is also accepted that the likelihood of developing a carcinoma increases with the duration of the colitis (Lagercrantz, 1955;Rosenqvist, Lagercrantz, Ohrling, and Edling, 1959;Slaney and Brooke, 1959), reaching definite clinical significance after 10 years (Hinton, 1966) and rising to an incidence of 56% after 30 years (de Dombal, Watts, Watkinson, and Goligher, 1966). These patients develop carcinoma at an unusually early age (Shands, Dockerty, and Bargen, 1952;Rosenqvist et al, 1959;Slaney and Brooke, 1959;Hodgson and Sauer, 1961;Edwards and Truelove, 1964).…”