After having read Parts I and II of this study, the reader surely realizes how much confusion exists about the true nature of an adenoma and how difficult it is for pathologists to identify some of these lesions as "still benign" or "already malignant" neoplasms. Some authors have been stuck between these two diagnoses and believed a lesion in between to be neither benign nor malignant, but rather premalignant. A review of literature made in the past and more recently of investigators from different parts of the worlds (especially Western and Japanese pathologists), shows that classifications and recommendations differ in the field of pathology and gastroenterology. Now, most pathologists and gastroenterologists still believe adenoma to be a benign tumor of colonic mucosa, and they continue to use dysplasia to describe it, or depending on how much they like to see or feel the lesion as ominous, they deal with an adenoma as a premalignant tumor. Borrowing such terms as dysplasia from gynecologic pathology by Morson or the creation of some terminologies such as "colorectal intraepithelial neoplasia" (CRIN) by Fenoglio and Pascal, clearly showed that colleagues went from specific diagnosis to nonspecific diagnosis. The CRIN is a description and not a diagnosis with specificity. It is meaningless and shrouds the true nature of this lesion.

Regarding dysplasia, it was primarily used to describe so-called adenomatous changes in ulcerative colitis and later was also used for pure adenomatous polyp of the colon, yet in both, the specific criteria for making the diagnosis were imperfectly described. Another conundrum is the grading of dysplasia. Colonic mucosal dysplasia was divided into mild, moderate, and severe, as first suggested by Morson, and then into two grades, low and high as suggested by the IBD-Dysplasia Study Group. The criteria for grading dysplasia are not consistent among pathologists from different parts of the world and are not even done consistently by the same pathologist. It is clear that the separation is absolutely subjective and firmly depends on the view and judgment of pathologists. Although every textbook of gastrointestinal pathology devotes plenty of space to describe dysplasia, in none of them can one find repeatable, reliable, understandable, and lucid criteria for histopathologic diagnosis of dysplasia of the colon. Much confusion has been created by the use of the word dysplasia for communication between pathologists and gastroenterologists. Nevertheless, the reader also must realize that treatment of adenomatous polyp in non-colitis patients or dysplasia or adenoma in patients with ulcerative colitis has not escaped from the controversies and disagreements.

However, the concept of the adenoma-carcinoma sequence and use of the term dysplasia has been criticized by some authors. In the textbook Surgical Pathology and Cytopathology, edited by Silverberg, the authors acknowledged that grading of dysplasia as mild, moderate, and severe is a deviation from the standard nomenclature of the IBD-Dysplasia Study Group (see above) and only "high grade dysplasia" could be easily recognized. [48] Although this "standard" nomenclature is not standard and the classification is very complex, acknowledging the inability to grade dysplasia by both systems by these authors is impressive. Genta believed that even the term "high grade dysplasia" is confusing and misleading and it should not be used at all. In fact "dysplasia" is more than a preneoplastic lesion; it is the earliest visible manifestation of neoplasia, the stage at which invasion has not yet occurred. [5] Finally, it is of interest to note a passage in Rosai and Ackerman's Surgical Pathology regarding adenomatous polyps. The author states, "In our opinion, adenomatous polyps, villoglanduar polyps, and villous adenomas are not adenomas (i.e., benign neoplasms of glandular tissue . . . They represent instead localized areas of epithelial dysplasia or atypical hyperplasia that have a tendency to protrude on the surface of the bowel (i.e., to become polypoid). From that point of view, the term adenomatous polyp (i.e., a protruding lesion that resembles an adenoma but is not) is a less inaccurate term than tubular adenoma, which firmly places this lesion into the erroneous category of a benign neoplasm." [49]

If adenomatous polyps are not adenoma, or benign neoplasms of glandular tissue, then what are they? In Part III, we will assess this mysterious lesion morphologically lesion based on our own material.