Is Familial Adenomatosis Coli Corroborative Evidence of the Adenoma-carcinoma Sequence "The Great Majority of Colorectal Carcinomas Arise from Adenoma"

Abstract

At present, the adenoma-carcinoma sequence of colorectal carcinomas " The great majority of colorectal carcinomas arise from adenomas " strongly insisted by Morson (1972), was been accepted in the world. Familial adenomatosis coli (FAC) has been produced as one piece of evidence in the sequence. However, it has been not clarified histopathologically whether the sequence holds good in FAC. The purpose of this study is to analyse the sequence in FAC.
Four cases of FAC totally resected the colorectum were histopathologically and morphometrically studied. Malignancies of polyps were objectively interpreted by using the indices of atypical grades (ING and ISA). The ING and ISA, ratio of area of adenomas to the flat mucosa, and number of polyps in unit area were measured by a computed image analyser.
According to the sequence, it is obvious that the probability of malignant transformation of adenoma (P) will be estimated by the formula P=CA/(AD+CA) where CA is number of carcinoma and AD number of adenoma. In the 4 cases, the mean of P showed 0.017. In the same manner, P in common cases of colorectal adenomas and carcinomas is estimated as 0.2 from the literatures.
Meanwhile, in a colorectal segment where adenomas were the most densely populated in the objects, the ratio of adenomatous area to the normal mucosa showed about 30%. When " P " is put as the probability of malignant transformation of adenoma and " P " as that of the normal mucosa per unit area, it is also clear according to the sequence that 3p: 7q=99 : 1 will hold good. Consequently, the ratio p/q is equal to 231. However, in the same way, the p/q estimated in common cases with adenomas or carcinomas of the colorectum become in about 100 times higher than that of FAC. Based on those data about-mentioned, it can be concluded that the probability of malignant transformation of adenoma in FAC is very low in comparison with that in common cases. Therefore, FAC dose not become as one piece of evidence providing we accept the sequence.
In 76 carcinomas measuring less than 2 cm in largest diameter and morphometriacally interpreted by using the indices of atypical grades (ING and ISA), de novo carcinomas were 48 representing 63% of the total, and the remnant 28 (37%) were carcinomas with adenomatous component. The proportion of the de novo to carcinoma having arisen from adenoma is similar to that previously reported by us. Regarding probabilities of P and p/q, if the histogenesis "The major part of colorectal carcinomas (70 to 80%) may arise from the flat mucosa independently of adenomas" proposed by us (1985) is taken into consideration, those two values in FAC and the common cases will become more close.