For almost all authors who have published works on adenomatous polyps, the close association between adenoma and carcinoma was obvious. Because most of these authors believed that there is conversion or transformation of an adenomatous polyp to carcinoma, many attempts were made to locate and define the transitional stage(s). Some authors considered all these "transitional stages" collectively as a condition named "precursor state" or "precancer lesion." The lesion designated with this opaque terminology was deemed to have been found in both long-standing ulcerative colitis and in an adenoma. However, it still was unclear what exactly the transitional forms were and what possibly could be the histopathologic criteria for diagnosis of it. The reader will learn in the following paragraphs that no agreement exists to this date in regard to definition and/or classification of these so-called transitional forms. Imprecise terminologies were created followed by diverse classifications and recommendations. Even recently, new terms have been introduced!

In 1967, Morson and Pang, who studied mainly ulcerative colitis, suggested first the new term "precancer" and then the term "dysplasia" to define so-called precursor or transitional forms morphologically in long-standing ulcerative colitis. [8] They were inspired by those colleagues who had studied gynecologic pathology and used the same terms, which in this area were used in cytology, for describing so-called precancerous cells of cervical mucosa. This is what Morson and Pang averred in their work in 1967 about the significance of finding a lesion called "precancer" in a patient with ulcerative colitis: "It is well recognized that the detection and treatment of precancerous lesions in an effective method of cancer control. The progress made in recent years in the screening of patients by biopsy and exfoliative cytology for precancer of the cervix is perhaps the best example." [8]

In 1973, Fenoglio and Pascal suggested the term "intraepithelial anaplasia" instead of precancer as suggested by Morson. [9] They acknowledged, however, that the term is descriptive and that a designation such as "intraepithelial carcinoma" is more justified. This is their definition of the term: "When cells confined to the epithelial layer of mucosa exhibited both a lack of differentiation and unrestricted replication as evidenced by mitotic activity at or near the luminal surface, the lesion so produce was classified as "intraepithelial carcinoma." In addition, there were loss of polarization, hyperchromatic and pleomorphic nuclei with irregular chromatin patterns and prominent nucleoli. With these criteria, although it might have been justified to use the term 'intraepithelial carcinoma' since the latter is not yet an accepted entity in ulcerative colitis; it was felt that a more descriptive name would be preferable. However, we consider these lesions to be similar if not identical to those described as "precancer" by Morson and Pang and as 'in situ carcinoma' by Evans and Pollock." [9]

However, a year later in an article written by Morson, he strictly employed the term "dysplasia" to define adenoma. "Adenomatous polyps and villous adenomas are the commonest names we give to a histologic spectrum which is all one process of epithelial dysplasia showing the same cytologic features which we recognize in other organs, for example in the cervix, as precancerous." [2]

A search through articles before 1975 revealed that Morson was the first to suggest "dysplasia" for description of the histologic changes in ulcerative colitis. He did not regard those changes to be a carcinoma. It is interesting that Morson introduced "dysplasia" in gastrointestinal pathology, more specifically colon pathology, nearly 25 years later after the suggestion of the same term by William Ober in 1949. Ober had suggested to Papanicolaou the term "dysplasia" for those cells in exfoliative cytology obtained from cervical mucosa that were not reactive nor of carcinoma. [10] This is the first record of the inappropriate use of the term dysplasia. Papanicolaou himself did not heed Ober's suggestion and never used the term later, but Reagan, another gynecologist, introduced it again in 1953 and together with Richart, Scott, and Patten played a major role in propagation of the term in gynecologic pathology. [11–12] The term "dysplasia" appeared attractive and was adopted by many pathologists in those years.

It is clear that before his article in 1974, Morson had thought about the creation of a similar system in gastrointestinal pathology like the one already used for cervical cancer in an early stage of development. He thought that such a system could also work for early detection of colonic cancer especially when it occurred along with severe inflammation of long-standing ulcerative colitis: "Here is a field in which exfoliative cytology of the colon may lead to the earlier diagnosis of malignant disease, for many of the malignant growths in ulcerative colitis are flat and infiltrating, and may be difficult to discover by radiological examination alone." [1]

Morson borrowed the term dysplasia from those gynecologists who had worked on cervical exfoliative cytology and applied it in colonic mucosa. At that time, he graded dysplasia as mild, moderate, and severe as Reagan had done it for cervical dysplasia. He first used the term for those changes that he had designated "precancer" in ulcerative colitis, but later he applied this system even for adenoma, which was deemed by him and many others who followed to be another precancerous lesion. In fact, the role of Morson in dysplasia in gastrointestinal pathology is the same as that of Reagan in gynecologic pathology. This is what Morson said about using and grading of dysplasia in an adenoma: "It is possible to grade polyps according to their cytologic features into those with mild, moderate and severe epithelial dysplasia. In general it is those with most severe dysplasia which have the greatest malignant potential. This is all part of the spectrum of neoplastic change in its benign or precancerous phase; that is, before actual invasion of normal tissues by abnormal cells takes place." [2]

Morson repeated his concept several times and continued the use of the word dysplasia in many other articles published by him between 1978 to 1993. [13–19] Here are some quotations verbatim from his articles:

"In this chapter adenomas as precancerous lesions, and the factors associated with malignant transformation of adenomas, will be discussed. The grading of adenomas into those showing mild, moderate, or severe dysplasia(see the previous chapter) has shown that , irrespective of histologic growth pattern, their malignant potential increases with increasing degree of atypia." [13]

"The precancerous lesion common to these is epithelial dysplasia which can occur in ordinary (foveolar) gastric epithelium as well as in intestinal metaplasia. The criteria for grading dysplasia in gastric epithelium into mild, moderate, and severe grades are given, and attention is drawn to the problems of differentiating inflammatory or regenerative change from mild dysplasia and intramucosal carcinoma from severe dysplasia. The clinical and epidemiological implications of gastric dysplasia are discussed with suggestions for further research." [14]

"Severe dysplasia and multiple adenomas could be valuable markers for selecting from the total adenoma population those most deserving of close surveillance in follow-up cancer prevention programs. Conceptually it would appear advantageous to think in term of the dysplasia-carcinoma sequence in the colorectum rather than the polyp-cancer or adenoma-carcinoma sequence." [15]